service manual
WARNING: If the information in these instructions is
not followed exactly, a fire or explosion may result
causing property damage, personal injury, or death.
—
Do not store or use gasoline or other flammable vapors and liquids in the vicinity of this or any other
appliance.
—
WHAT TO DO IF YOU SMELL GAS
• Evacuate all persons from the vehicle.
• Shut off the gas supply at the gas container or
source.
• Do not touch any electrical switch or use any
phone or radio in the vehicle.
• Do not start the vehicle’s engine or electric
generator.
• Contact the nearest gas supplier or qualified
service technician for repairs.
• If you cannot reach a gas supplier or qualified
service technician, contact the nearest fire
department.
• Do not turn on the gas supply until the gas leak(s)
has been repaired.
—
Installation and service must be performed by a qualified installer, service agency, or the gas supplier.
SERVICE MANUAL
AHE-375-P02
© 2012 Aqua-Hot Heating Systems Inc.
Table of Contents
General Information
Danger, Warning, Caution, and Note Box Definitions................................................... Page 6
Section 1: Introduction To The Aqua-Hot 375-LP
Technical Information ................................................................................................... Page 7
I.D. Label Sample ........................................................................................................ Page 8
Operating Instructions .................................................................................................. Page 9
Aqua-Hot Heater Overview .......................................................................................... Page 10-12
Aqua-Hot Operational Flow-Chart ................................................................................ Page 13
Antifreeze and Water Heating Solution……………………………………………………..Page 14-15
Section 2: Interior Switch Panel
Propane-Burner Switch ................................................................................................ Page 16
Electric Element Switch ................................................................................................ Page 16
Switch Panel Wiring Schematic .................................................................................. Page 17 - 19
Section 3: Exhaust System
Exhaust System Requirements .................................................................................... Page 20
Section 4: Aqua-Hot Components
Interlock Switch ............................................................................................................ Page 21
Float Switch .................................................................................................................. Page 22-23
Propane-Burner Control Thermostat ............................................................................ Page 23-24
Electric Element Control Thermostat ............................................................................ Page 25-26
Electric Element High Limit Thermostat ....................................................................... Page 27
Propane-Burner High Limit Thermostat (Left) .............................................................. Page 28
Propane-Burner High Limit Thermostat (Right) ............................................................ Page 29
Low Temperature Cutoff Thermostat ............................................................................ Page 30-32
Interior Heating Zone Check Valve............................................................................... Page 33-34
Domestic Water Tempering Valve ................................................................................ Page 35-36
Interior Heating Zone Circulation Pumps 1 & 2 ............................................................ Page 37-39
Stir Pump (Circulation Pump #2) .................................................................................. Page 40
Electric Heating Element .............................................................................................. Page 41-42
Electric Heating Element A.C. Relay ............................................................................ Page 43-44
Interior Heating Zone Relay - Heat Exchanger Fans .................................................... Page 45-46
Interior Heating Zone Relay - Circulation Pump ........................................................... Page 47-48
Interior Heating Zone Relay - Replacement Procedure ................................................ Page 49
© 2012 Aqua-Hot® 375P02-LP Hydronic Heating System Service Manual—Rev. D
Table of Contents
Section 5: Filling/Draining The Aqua-Hot 375P With Heating Solution
Filling the Aqua-Hot ................................................................................................ Page 50-52
Draining the Aqua-Hot ............................................................................................ Page 53
Section 6: Propane-Burner
General Recommended Maintenance ...................................................................... Page 54
General Component Overview ............................................................................... Page 55-56
Propane-Burner Operational Overview .................................................................... Page 57
Controller Wiring Schematic ................................................................................... Page 58
Section 7: Detaching and Reattaching the Propane-Burner
Detaching the Burner ............................................................................................. Page 59-62
Reattaching the Burner...…………………………………………………………………Page 63-66
Section 8: Propane-Burner Components and Repair Information
Mounting Gasket .................................................................................................... Page 67
Hot Surface Igniter ................................................................................................. Page 67-69
Insulation, Refractory ............................................................................................. Page 70-71
Dual Stage Propane Gas Valve.............................................................................. Page 72-73
Combustion Blower Fan ......................................................................................... Page 74-75
Exhaust “High Back Pressure” Switch .................................................................... Page 76
Fan Validation Switch ............................................................................................. Page 77
Fan Validation Switch Relay ................................................................................... Page 78
Buck Boost Converter (Combustion Blower Fan) ................................................... Page 79
Buck Boost Converter (Hot Surface Igniter) ........................................................... Page 80
Flame Sensor ......................................................................................................... Page 81
Fenwal Burner Controller ....................................................................................... Page 82-84
© 2012 Aqua-Hot® 375P02-LP Hydronic Heating System Service Manual—Rev. D
Table of Contents
Section 10: Troubleshooting
The Propane-Burner switch has been turned on; however, the Propane-Burner fails
to operate ..................................................................................................................... Page 85
The Propane-Burner switch has been turned on and the Propane-Burner’s Blower
Motor has begun to operate; however, the Propane-Burner does not ignite ................ Page 86
The Propane-Burner switch has been turned on; however, multiple attempts are
required before the Propane-Burner will ignite ............................................................. Page 86
The Aqua-Hot’s exhaust system “woofs/pops” when the Propane-Burner Ignites ........ Page 86
The Propane-Burner will ignite, but short cycles (only runs for a short amount of
time before shutting down) ........................................................................................... Page 86
The Aqua-Hot is operating, but an interior and/or fresh water tank heating zone is
not working….…………………………………………………………..……………………..Page 87
The Aqua-Hot is at operating temperature; however, the interior and/or fresh
water tank heat exchanger fans are not operating ....................................................... Page 87
The Aqua-Hot is operating, but the domestic hot water system is not producing
hot water ...................................................................................................................... Page 87
The Electric Element switch has been turned on; however, the Aqua-Hot’s
120 Volt-AC electric heating element does not operate ............................................... Page 88
Appendix A: Wiring Diagram .........................................................................................Page 89-91
Appendix B: Wire Gauge Chart ........................................................................................... Page 92
Appendix C: Winterization Process.................................................................................... Page 93
Appendix D: Extreme Cold Weather Operation ............................................................Page 94-95
Appendix E: Propane Burner Combustion Air Adjustment Procedure .....................Page 96-97
© 2012 Aqua-Hot® 375P02-LP Hydronic Heating System Service Manual—Rev. D
GENERAL INFORMATION:
This manual is designed to aid trained and qualified service
technicians with the process of troubleshooting and servicing
the Aqua-Hot 375-LP Hydronic Heating System.
The Aqua-Hot features a 12 Volt-DC powered PropaneBurner and a 120 Volt-AC, 1500-Watt Electric Heating Element. These two heating sources are used in conjunction
with an FDA approved “GRAS” (Generally Recognized as
Safe) propylene glycol based boiler antifreeze and water
heating solution in order to provide a continuous supply of
domestic hot water, interior/fresh water tank heating, independent interior zone heating.
Please note that all Danger, Warning, Caution, and Note boxes, appearing as needed throughout this manual, must be
reviewed and adhered to during servicing of the Aqua-Hot in
order to avoid potential hazards which could result in injury,
death, product damage, and/or property damage.
Should additional assistance be needed, please contact the
Technical Support Department at 1-800-685-4298, Monday
through Friday between the hours of 7:00 AM and 4:00 PM
Mountain Standard Time.
Danger, Warning, Caution, and Note Box Definitions
Danger, Warning, Caution, and Note boxes appear throughout this manual as a means of alerting the service technician
to important information.
Indicates that personal injury is likely or imminent
Indicates that serious damage to the heater will occur
and personal injury is possible as well.
Indicates that damage to the heater is possible.
NOTE: Indicates information that requires special
attention by the service technician.
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 6 —
SECTION 1: INTRODUCTION
TO THE
AQUA-HOT 375-LP
Figure 1
Propane Burner, Heat Input (Firing Rate)................................................................................................................................. 64,377 BTU/hr
Propane Burner, Fuel Consumption (Continuous Operation) ............................................................................. 0.72 gal/hr, 2.72 liters/hr
Heater, Voltage/Maximum Power Consumption .......................................................................................................12 Volt-DC/122 watts
Electric Heating Element specifications .................................................................................................................... 120 Volt-AC/1500 watts
Zone Heat Circulation Pump specifications ....................................................................................................(2) 12 Volt-DC/21 watts each
Number of Heating Zones ..............................................................................................................maximum of 2, plus Bay Heat Exchanger
Domestic Water Heating Capacity ................................................................................................................................continuous/on-demand
Dimensions ...................................................................................................................................................................16.75”H x 18”W x 29.5”L
Dry Weight .......................................................................................................................................................................... approximately 155 lbs.
Wet Weight.......................................................................................................................................................................... approximately 200 lbs.
NOTE: All vehicle installations must comply with the requirements listed in the Recreational Vehicle Industry Association’s (RVIA) ANSI/NFPA 1192 Handbook for Recreational Vehicle Standards. To receive a copy of this handbook
and other pertinent RVIA Standards, write to: Recreation Vehicle Industry Association, 1896 Preston White Drive,
P.O. Box 2999, Reston, VA 22090-0999, call them at (703) 620-6003, or visit them online at www.rvia.org.
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 7 —
SECTION 1: INTRODUCTION
TO THE
AQUA-HOT 375-LP
For installation only in a compartment that is completely closed off from living quarters and accessible only from the outdoors.
The Exhaust System MUST NOT terminate beneath
the vehicle or under an openable window or vent.
Combustion Air MUST BE supplied from outside
the vehicle.
CAUTION: THIS APPLIANCE OPERATES ON BOTH
AC AND DC POWER,
USE COPPER CONDUCTORS ONLY!
Use a 25-Amp fuse for over-current protection for
the DC power supply.
Use a circuit breaker that cuts power at 20-Amps
maximum for over-current protection for the 120VAC power supply.
Mount the Heater near a bay/storage door so that
the Access Cover can be easily removed for service.
WARNING: DO NOT OPERATE APPLIANCE WITH
ACCESS COVERS REMOVED.
Minimum Heater Clearances:
Front—Open Access
Back— 0 inches
Top — 6 inches
Sides—0 inches
Install in strict compliance with local codes, NFPA
1192, and the manufacturer’s instructions
Minimum Heater Clearances:
Front - Open Access
Back - 0 inches
Top - 6 inches
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 8 —
SECTION 1: INTRODUCTION
TO THE
AQUA-HOT 375-LP
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 9 —
SECTION 1: INTRODUCTION
TO THE
AQUA-HOT 375-LP
Figure 2
Pump-1 and
Pump-2 Inlet
Ports
Zone 1 and 2
Outlet Ports
I.D. Label
Propane Inlet
Hot Water
Outlet Port
Terminal Block
Access Area
Cold Water
Inlet Port
Operating
Instructions
Site Access
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 10 —
SECTION 1: INTRODUCTION
TO THE
AQUA-HOT 375-LP
12
Propane Burner
High-Limit Thermostats
11
Figure 3
Float Switch
1
10
Low Temp. Cut-off
Thermostat
13
2
Propane Burner
Control Thermostat
3
9
14
6
8
4
5
7
1
2
3
4
5
6
INTERLOCK SWITCH
ZONE-1 RELAY
ZONE-2 RELAY
FUSE BLOCK
CIRCULATION PUMP - ZONE 1
PROPANE-BURNER
7
8
9
10
11
12
SYSTEM DRAIN
PROPANE-BURNER CONTROLLER
PROPANE BURNER CONTROL THERMOSTAT
LOW TEMPERATURE CUT-OFF THERMOSTAT
FLOAT SWITCH
DIESEL-BURNER HIGH-LIMIT THERMOSTATS
Electric Element High-Limit Thermostat
13
Electric Element Control Thermostat
14 1500 Watt Electric Element
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 11 —
SECTION 1: INTRODUCTION
TO THE
AQUA-HOT 375-LP
Figure 4
120 Volt-AC
Relay
Zone 1 Relay
Zone 2 Relay
Fuse Block
Ground Strip
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 12 —
SECTION 1: INTRODUCTION
Chart 1
TO THE AQUA-HOT
375-LP
Aqua-Hot Operational Flowchart
Heat source is selected from the
Interior Switch Panel.
Propane-Burner is activated
by the Burner switch.
Electric Heating Element is
activated by the Electric
switch.
The Boiler Tank heats the
antifreeze and water heating
solution to 190*F.
Heating Zone Thermostat
calls for heat.
The heated antifreeze and water heating
solution flows through the Hydronic Heating System transferring heat to the heat
exchanger, which is, in turn, transferred to
the surrounding zone.
A hot water faucet (e.g., kitchen
sink, shower, etc.) is opened.
Continuous hot water is supplied
to the faucet.
The cooled antifreeze and water heating
solution is returned to the boiler tank to
be reheated.
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 13 —
SECTION 1: INTRODUCTION
Antifreeze and Water Heating Solution:
As the antifreeze type and mixture ratio is essential to the
Aqua-Hot’s performance and ability to comply with regulations, the following information is being supplied to
understand various types of antifreeze, the quality of water necessary, and the mixture ratio. Aqua-Hot Heating
Systems Inc. recommends CAMCO’s Boiler Antifreeze 100°.
TO THE AQUA-HOT
375-LP
tivity characteristics. Although these types of antifreeze
products are considered less toxic and safer than ethylene
glycol for people, pets, and the environment, they are not
“Generally Recognized as Safe” (GRAS) rated by the FDA.
Therefore, they must be marked with a “harmful if swallowed” warning. This additional warning is required because these types of antifreeze products contain high levels
of chemical inhibitors. Due to their potentially hazardous
properties, they should never be used in the Aqua-Hot’s
Hydronic Heating System.
Antifreeze Types:
Antifreeze Mixture Water Quality:
The following information addresses the necessary usage of
a propylene glycol based “boiler “ type antifreeze in the Aqua-Hot. Propylene glycol is a safer alternative to the more
toxic ethylene glycol antifreeze; however, as mandated by
IAPMO (International Association of Plumbing and Mechanical Officials), only those propylene glycol based “boiler”
type antifreezes deemed “Generally Recognized as
Safe” (GRAS) by the FDA should be utilized.
Because of the significant impact various types of antifreeze
can have on a hydronic heating system, including the level of
safety provided, it has been recognized that there is a need to
provide an explanation regarding two additional prominent
types of antifreeze/coolant available. The following information should be utilized as an educational means of ensuring that the proper type of propylene glycol based antifreeze
is selected:
RV & Marine Antifreeze:
These types of propylene glycol based antifreeze products
are formulated specifically for “winterizing” applications
only. Although RV & Marine antifreeze is often “Generally
Recognized as Safe” by the FDA, it should never be used in
the Aqua-Hot’s Hydronic Heating System Boiler Tank. This
type of antifreeze is not formulated to transfer heat, which is
essential to the heating system’s functionality and does not
contain rust inhibitors. Please note, however, that RV &
Marine antifreeze can be utilized to winterize the Aqua-Hot’s
domestic water heating system.
Automotive Antifreeze/Coolant:
These types of propylene glycol based antifreeze products
are formulated specifically to protect automotive engines
against corrosion, freezing temperatures, and overheating.
They also have excellent heat transfer and thermal conduc-
In order to ensure maximum performance and longevity of
an Aqua-Hot heating system’s boiler tank and associated
components, it has been determined that there is a need to
use distilled, de-ionized, or soft water in combination with
concentrated propylene glycol for the Aqua-Hot’s antifreeze
and water heating solution,. Please note that this is only necessary when mixing concentrated propylene glycol antifreeze
with water; suppliers of pre-mixed antifreeze are responsible
for the use of high-quality (distilled, de-ionized, or soft) water when preparing their antifreeze for sale.
Hard water possesses a high-level of calcium and magnesium
ions, which deplete the propylene glycol antifreeze’s corrosion inhibitors. This, in turn, causes the antifreeze and water
heating solution to begin turning acidic, which can corrode
the Aqua-Hot’s boiler tank and associated components prematurely. Therefore, concentrated propylene glycol should be
diluted with distilled, de-ionized, or soft water that is 80 ppm
or less in total hardness. The local water agency should have
up-to-date water quality reports that should indicate if the
local tap water is within this guideline.
Antifreeze Terms and Mixture Ratio:
The following information addresses the process of selecting
an antifreeze and water mixture ratio that provides adequate
freeze, boiling, and rust/anti-corrosive protection. A 50/50
mixture ratio is recommended, which will result in a freeze
point of approximately -28°F and a boil point of approximately 222°F.
The following information should be utilized for the purpose
of clarifying some terms commonly associated with antifreeze.
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 14 —
SECTION 1: INTRODUCTION
Freeze Point and Burst Point:
Antifreeze lowers the freezing point of any liquid, to which it
has been added, by preventing the formation of ice crystals;
however, as the ambient temperature continues to decline,
the water in the solution will attempt to attain a solid state.
The point in which the water begins to solidify is termed the
“Freeze Point.” Although the water in the solution has begun to freeze, producing a “slushy” consistency, the antifreeze in the solution will continue to combat the normal
expansion of the solution as it freezes. The point in which
the solution can begin to expand, due to colder temperatures,
is called the “burst point.” Once the solution reaches the
burst point, the potential is present for ruptured pipes to exist. The burst point of the antifreeze and water heating solution is dependent upon the brand of propylene glycol employed.
TO THE
AQUA-HOT 375-LP
Antifreeze is also primarily responsible for heat transfer
characteristics. Therefore, as water is an excellent heat conductor, it is added to the mixture. A 50/50 solution of propylene glycol antifreeze and water is recommended to provide the best performance combination of the aforementioned functions. If excess propylene glycol exists within an
antifreeze and water heating solution, the water’s heat absorption properties are compromised, which could ultimately
inhibit the Aqua-Hot from providing adequate domestic hot
water and interior heating.
Additionally, if the antifreeze and water heating solution
contains over 70 percent antifreeze, the freezing point is actually raised, resulting in less freeze protection.
Boiling Point:
The Aqua-Hot utilizes the antifreeze and water heating solution as a transportation means for the heat produced from the
internal processes. The antifreeze absorbs the heat created
until its boiling point is reached; it is at this point that the
liquid turns to a gas and is expelled to prevent the heating
system from overheating. Each time the boiling point is
reached, a loss of efficiency occurs because the heat produced is expelled rather than used for the function of the
heating system. Therefore, a higher boiling point is desired
in order to combat the loss of efficiency, which allows the
antifreeze to transport the heat created from the internal process throughout the motor home where it can be used productively rather than dissipating due to its change from a
liquid to a gas.
Rust and Anti-Corrosive Inhibitors:
Another major function of antifreeze is to provide protection
to the internal metal components of the Aqua-Hot Hydronic
heating system from corrosion and rust. Antifreeze is able to
perform this function by the addition of rust- and anticorrosive inhibitors, which are designed specifically to activate in a water solution.
Summary:
Antifreeze has three basic functions: freeze protection, boilover protection, and anti-corrosion and rust protection.
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 15 —
SECTION 2: INTERIOR SWITCH PANEL
Figure 5
Electric Element Switch:
Propane Burner Switch:
The Propane-Burner switch activates the Aqua-Hot’s Propane-Burner; reference Figure 5. This procedure allows the
Propane-Burner to operate and supply heat to the Aqua-Hot’s
Boiler Tank, which will heat the Aqua-Hot’s antifreeze and
water heating solution to the maximum operating temperature of 190±5°F in approximately 10-20 minutes.
The indicator light, will illuminate whenever the PropaneBurner switch is in the ON position.
Please note that the Propane-Burner is the Aqua-Hot’s primary heat source for heating both the interior and/or the
domestic hot water (such as when cool ambient temperatures
exist and/or when there is a high demand for domestic hot
water).
NOTE: If the burner switch light fails to illuminate makes
sure the access cover is properly installed. Also, if the heater is low on the water/antifreeze solution both the burner and
the electric lights will be out.
NOTE: This feature is only operational whenever the
Motor home is connected to 120 Volt-AC power or
when the generator is operating.
The Electric Element switch activates the Aqua-Hot’s 120
Volt-AC Electric Heating Element; reference Figure 5. This
procedure allows the 120 Volt-AC Electric Heating Element
to operate and supply heat to the Aqua-Hot’s Boiler Tank,
which will heat the Aqua-Hot’s antifreeze and water heating
solution to the maximum operating temperature of 190±5°F
in approximately 1-2 hours.
The indicator light, adjacent to the Electric Element switch,
will illuminate whenever the Electric Element switch is in
the ON position.
Please note that the 120 Volt-AC Electric Heating Element is
the Aqua-Hot’s secondary heat source for heating both the
interior and/or the domestic hot water during low heating
demand situations (such as when moderate ambient temperatures exist and/or when there is a low demand for domestic
hot water).
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 16 —
SECTION 2: INTERIOR SWITCH PANEL:
MANUFACTURED BEFORE
JANUARY 2011
Figure 6a
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 17 —
SECTION 2: INTERIOR SWITCH PANEL:
MANUFACTURED BETWEEN
JANUARY 2011 TO AUGUST 2011
Figure 6b
Figure 6c
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 18 —
SECTION 2: INTERIOR SWITCH PANEL:
MANUFACTURED AFTER
09/01/2011
Interior Switch Panel, Rear View
Figure 6d
Jumper Wire
10
Switch
Burner
Switch
Electric Element
Switch
9
10
2
2
4
4
Mount Location
9
Switch
Mount Location
Pin# 2
Terminal Block AO
Pin# 2
Terminal Block DO
Pin# 4
Terminal Block A1
Pin# 4
Terminal Block D1
Pin# 10
Jump to Pin # 5
Pin# 10
Terminal Block L+
Pin# 9
Chassis Ground
Pin# 9
Terminal Block L-
Electric Element Switch to
Terminal Block Connections
Burner Switch to
Terminal Block Connections
Figure 6e
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 19 —
SECTION 3: EXHAUST SYSTEM REQUIREMENTS
Because the Aqua-Hot’s exhaust is hot and must be kept
away from any heat-sensitive material, the exhaust system
should be checked to ensure that it continues to meet the
following requirements:

The exhaust must not be directed downward as a fire
could result when parked in dry, grassy areas.

The exhaust must not terminate underneath the vehicle,
underneath an openable window or vent, in the awning
area of the motor home (if applicable), or near slide-out
areas.


A maximum of one 90° and one 45° exhaust pipe bends
are allowed.

The exhaust must be able to freely exit away from the
vehicle without any obstructions.

Two-inch standard automotive-type exhaust piping
should be used with a maximum of two 90-degree pipe
bends and should not exceed 11 feet.

The Exhaust Tip must be used to deflect wind gusts
NOTE: The Exhaust Tip has a required clearance of one
inch between the band on the exhaust tip and the end of the
exhaust pipe. Improper installation of the exhaust tip may
result in the propane burner “short cycling” due to back
pressure.

The 3-inch and 4-inch black-pipe nipples and the exhaust elbow - originally supplied with the Aqua-Hot,
must be present.

The exhaust should be inspected for excessive bends,
excessive length, kinks or any type of restriction.
The total length of the exhaust pipe shall not exceed 11’.
Figure 7
Exhaust Tip
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 20 —
SECTION 4: AQUA-HOT COMPONENTS
This section details various components of the Aqua-Hot
that may require troubleshooting and/or replacement in
the event of a malfunction. The Propane-burner and its
components are detailed in Section 8 of this manual.
If continuity is not present with the button pushed in, follow
the instructions in this section to replace the interlock switch.
Replacement Procedure:
Replacement parts can be ordered through Aqua-Hot’s
Web site at www.aquahot.com or by calling 1-800-6854298.
FAILURE TO DISCONNECT ALL POWER SUPPLIES AND/OR
TO ALLOW THE HEATER TO COOL BEFORE SERVICING
If additional assistance is needed, the Technical Support
Team can also be reached, Monday through Friday, from
7:00 AM to 4:00 PM Mountain Standard Time at 1-800685-4298.
COULD CAUSE SERIOUS DAMAGE OR PERSONAL INJURY.
1.
Disconnect the interlock switch’s wires by pulling the
quick connectors from the switch’s spade terminals.
2.
Release the interlock switch from the Aqua-Hot cabinet
by pushing in on the locking tabs and pulling the interlock switch.
3.
Remove the defective interlock switch from the AquaHot.
4.
Install the replacement interlock switch onto the AquaHot ensuring that the locking tabs snap into place.
5.
Connect the Aqua-Hot’s wires to the replacement interlock switch with yellow wire #31 connected to the terminal labeled “NO” and yellow wire #9 connected to the
terminal labeled “COM.”
Sensors/Switches
Interlock Switch:
The interlock switch is a safety device designed to ensure
that the Aqua-Hot’s access cover is securely installed before
allowing the Propane-Burner to operate. For location of interlock switch reference Figure 3.
Note: If the cover is removed or the interlock switch is defective the Propane-burner switch indicator light will not
illuminate.
Troubleshoot the interlock switch if the following condition
has occurred:


The Propane-Burner fails to operate.
The light on the Burner Switch fails to illuminate.
NOTE: If the interlock switch’s wires are reversed, the
interlock switch will only allow the Propane-Burner to
operate when the access cover is removed and the button on
the switch is released.
Troubleshooting:
NOTE: The interlock switch will prevent the PropaneBurner from operating without the access cover intact; therefore, the switch will need to be manually pressed during testing for the switch’s functionality.
1.
Turn the Propane-Burner switch on, from the interior
switch panel and ensure that the boiler tank has sufficiently cooled in order to require heat from the Propaneburner.
2.
Disconnect the yellow and white wires from the interlock switch noting that wire #31 is connected to the terminal labeled “NO” and wire #9 is connected to the terminal labeled “COM.”
3. Using an ohmmeter, check the interlock switch for
continuity while the button is pushed in.
Figure 8
Connect
Wire # 9
“COM”
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
Connect
Wire # 31
“NO”
— Page 21 —
SECTION 4: AQUA-HOT COMPONENTS
Replacement Procedure:
Float Switch:
The Float Switch monitors the level of antifreeze and water
heating solution within the Aqua-Hot’s boiler tank to ensure
that an adequate volume exists. Reference Figure 9 for location.

TO ALLOW THE HEATER TO COOL BEFORE SERVICING
COULD CAUSE SERIOUS DAMAGE OR PERSONAL INJURY.
1.
Ensure that the Aqua-Hot has been completely shut
down and that all power sources have been disconnected. Also, because this replacement procedure will
involve the boiler tank and the potential for hot coolant,
be sure the heater has adequately cooled.
2.
Drain the antifreeze and water heating solution from the
Aqua-Hot’s boiler tank using the drain valve, Approximately 2 gallons will need to be drained..
3.
Disconnect the float switch’s wires by separating the
quick-disconnect terminals.
4.
Using a 7/8 socket, remove the defective float switch
from the Aqua-Hot’s boiler tank.
5.
Verify Fuse “B”, on the Fuse Block is sending power to
the float switch.
Wrap the threads of the replacement float switch with a
thread seal tape.
6.
Inspect the wire harness for damaged or severed wires.
If no wires are found to be damaged or severed,
continue.
Screw the replacement float switch into the port on the
Aqua-Hot’s boiler tank and tighten securely with a 7/8
socket, ensuring the N.O. stamp in on top.
7.
Connect the replacement float switch’s wires in the
same configuration as the removed float switch’s wires.
8.
Refill the Aqua-Hot’s Boiler tank with the proper water/
antifreeze mixture. Reference Section 5 in this manual
for instructions on filling and draining the Aqua-Hot
unit.
Troubleshoot the Float Switch if one of the following conditions has occurred:

FAILURE TO DISCONNECT ALL POWER SUPPLIES AND/OR
The Propane-Burner and/or Electric Heating element fail
to operate.
The Propane Burner and/or Electric Heating Element
Switches Fail to illuminate.
Troubleshooting:
1.
2.
3.
4.
5.
Verify that the Aqua-Hot’s boiler tank is full of the antifreeze and water heating solution.
Verify that the connections for the wires on the float
switch are securely plugged into the wiring harness.
Verify the functionality of the Float Switch by
completing the following:
A. Disconnect the wires from the Float Switch.
B. Install a jumper wire between the wires on the harness, #65 & #66, in order to bypass the Float
Switch.
If the Propane-Burner and/or electric heating element come on when the jumper wire is installed,
follow the instructions in this section to replace the
float switch
9. Test for proper operation.
Be sure to install the replacement float switch with
the “N.O.” stamp on top, failure to do so, will allow
the diesel/electric to come on with no antifreeze in
the boiler tank.
NOTE: The Float Switch can be tested by performing a
Continuity Test. With the heater full of antifreeze there
should be continuity between the wires on the Float Switch.
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 22 —
SECTION 4: AQUA-HOT COMPONENTS
Figure 9
Float Switch
Thermostats
Control Thermostat: Propane-Burner
The Propane Burner’s control thermostat is installed into the
Aqua-Hot’s boiler tank and monitors the temperature of the
antifreeze and water heating solution to determine when it is
at operating temperature and when it requires heat. The Aqua-Hot is considered to be at operating temperature between
158°F and 190°F. Reference Figure 10 for the location of
the Control Thermostat..
Troubleshoot the control thermostat if one of the following
conditions has occurred:


The Propane-Burner Fails To operate.
There is a lack of hot domestic water and interior heat.
If there is no continuity, follow the instructions in
this section for replacing the control thermostat.
If continuity exists, complete the following:
1.
Turn the Propane-Burner switch on from the interior
switch panel and ensure that the boiler tank has sufficiently cooled in order to require heat from the dieselburner.
Inspect the control thermostat’s wiring and
connections for any signs of damage or
corrosion.
C. If the Propane-Burner does come and run, but there
is still a lack of domestic hot water/interior coach
heat:
1.
Troubleshooting:
1.
B. Disconnect the control thermostat’s wires from their
connections, and, using an ohmmeter, check for
continuity.
Check operational temperature of the control
thermostat by using a digital thermometer. If
the temperature range of the control thermostat
is not within specifications, replace the control
thermostat.
Note: The operational range of the Propane-Burner ‘s
If the burner does not come on and run, check the following:
control thermostat is 158° F - 190° F.
A. Verify that the temperature of the boiler tank has
fallen below the 158°F minimum operating
temperature by checking with a digital thermometer.
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 23 —
SECTION 4: AQUA-HOT COMPONENTS
Replacement Procedure:
FAILURE TO DISCONNECT ALL POWER SUPLIES AND/OR TO
4.
Using a 7/8 socket, unscrew the control thermostat from
the Aqua-Hot’s boiler tank.
5.
Wrap the threads of the replacement control thermostat
with a thread seal tape.
6.
Screw the replacement control thermostat into the port
on the Aqua-Hot boiler tank and tighten securely with a
7/8 socket.
7.
Reconnect control thermostat wires.
8.
Refill the Aqua-Hot boiler tank with the antifreeze and
water heating solution.
9.
Test the Aqua-Hot for normal operation using a digital
thermometer.
ALLOW THE HEATER TO COOL BEFORE SERVICING COULD
CAUSE SERIOUS DAMAGE OR PERSONAL INJURY.
1.
2.
3.
Ensure that the Aqua-Hot has been completely shut down
and that all power sources have been disconnected. Also,
because this replacement procedure will involve the boiler
tank and the potential for hot coolant, be sure the heater
has adequately cooled.
Drain 2 gallons of the antifreeze and water heating solution from the Aqua-Hot boiler tank using the drain valve.
Disconnect the defective control thermostat’s wires by
separating the quick-disconnect terminals. Reference
Figure 10 for location.
Figure 10
185 °F Propane Burner
Control Thermostat
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 24 —
SECTION 4: AQUA-HOT COMPONENTS
Thermostats (continued)
Control Thermostat: Electric Element
The control thermostat for the 120 VAC Electric Heating
Element is installed on the Aqua-Hot’s boiler tank and monitors the temperature of the antifreeze and water heating solution to determine when it is at operating temperature and
when it requires heat. The Aqua-Hot is considered to be at
operating temperature between 158°F and 190°F.
Troubleshoot the electric element control thermostat if one of
the following conditions has occurred:


The Electric Element Fails To operate.
There is a lack of hot domestic water and interior heat.
For continuous domestic hot water to be present,
the Propane-Burner must also be selected as a heating
source.
NOTE:
Troubleshooting:
1.
2.
Turn the electric element switch on from the interior
switch panel and ensure that the boiler tank has sufficiently cooled in order to require heat from the electricelement.
Using a Digital Clamp-on Amp meter, place it around
the Black wire, #51, coming off of the electric element.
Set the Clamp-on Amp meter to register AC amps.
The 1500 Watt electric element should pull 11.5 12.5amps.
NOTE: The coach must either be plugged into shore power,
If the Electric Element is not within spec check the
following:
FAILURE TO DISCONNECT ALL POWER SUPPLIES AND/OR TO
ALLOW THE HEATER TO COOL BEFORE SERVICING COULD
CAUSE SERIOUS DAMAGE OR PERSONAL INJURY.
A. Verify that the temperature of the boiler tank has
fallen below the 158°F minimum operating
temperature by checking with a digital thermometer.
B. Disconnect the control thermostat’s wires, #52 &
#54, from their connections, and, using an
ohmmeter, check for continuity on the control
thermostat.
If there is no continuity, follow the instructions in
this section for replacing the control thermostat.
3. If the Electric Element does come and run, but there is
still a lack of domestic hot water/interior coach
heat:
1. Check operational temperature of the control
thermostat by using a digital thermometer.
If the temperature range of the control thermostat is
not within specifications, replace the control
thermostat.
Note: The operational range of the Electric Element
control thermostat is 158° F - 190° F.
or the generator must be on, for there to be 120vac at the
heater.
Figure 11
185° F
Control Thermostat
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 25 —
SECTION 4: AQUA-HOT COMPONENTS
Thermostats (continued)
Control Thermostat: Electric Element
(continued)
Replacement Procedure:
1. Ensure that the Aqua-Hot has been completely
shut down and that all power sources have been
disconnected.
2. Locate the control thermostat for the electric
element. Reference Figure 12.
3. Disconnect the defective control thermostat’s
wires by separating the quick-disconnect terminals.
4. Using a 5/8 wrench or socket, remove the defective control thermostat from the Aqua-Hot.
5. Install the replacement control thermostat, tightening only to 15 in/lbs. Do not over-tighten.
6. Connect the replacement control thermostat’s
wires in the same configuration as the removed
thermostat’s wires.
7. Test for proper operation, by using a digital
thermometer.
NOTE: The coach must either be plugged into shore
power, or the generator must be on, for there to be
120 VAC at the heater.
Figure 12
185° F
Control Thermostat
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 26 —
SECTION 4: AQUA-HOT COMPONENTS
AC High-Limit Thermostat:
The AC high-limit thermostat serves as a safety measure in
the event that the electric heating element continues to operate after the maximum operating temperature is reached.
The high-limit thermostat allows the current for the heating
element to pass through it until the boiler tank reaches a temperature of 215°F. Should this temperature be reached, the
high-limit thermostat blocks the current to the element,
which prevents it from continuing to provide heat to the boiler tank.
NOTE: If the high limit thermostat is tripped, it is recommended to test both the A.C. and D.C. control thermostats
for proper operation.
Replacement Procedure:
FAILURE TO DISCONNECT ALL POWER SUPPLIES AND/OR
TO ALLOW THE HEATER TO COOL BEFORE SERVICING
COULD CAUSE SERIOUS DAMAGE OR PERSONAL INJURY.
1.
Ensure that the Aqua-Hot has been completely shut
down and that all power supplies have been
disconnected.
2.
If applicable, remove the heat shrink insulation covering
the wires and terminals on the defective high-limit thermostat.
3.
Remove the two wires from the defective high-limit
thermostat by pulling firmly on the wires.
4.
Using a 5/8 wrench or socket, remove the defective high
-limit thermostat from the Aqua-Hot’s boiler tank.
5.
Install the replacement high-limit thermostat into the
port on the Aqua-Hot’s boiler tank and finger-tighten
only (15 in/lbs). Do Not Over-Tighten.
If there is no continuity, press the white reset button on
the thermostat and re-check for continuity.
6.
Connect the wires removed from the defective high-limit
thermostat to the replacement high-limit thermostat.
If continuity is still not present after the reset button has
been pressed, follow the instructions in this section to
replace the AC high-limit thermostat.
7.
Test for normal operation.
Troubleshoot the AC high-limit thermostat if the following
condition has occurred:

The electric heating element fails to operate.
Troubleshooting:
1.
Disconnect all power supplies.
2.
Verify that the boiler tank’s temperature is below 215°F.
3.
Locate the AC high-limit thermostat and remove its
wires. Reference Figure 13 for location
4.
Using a digital volt meter, set to check continuity, check
the thermostat for continuity.
Figure 13
215* A.C. High Limit Thermostat
Reset Button
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 27 —
SECTION 4: AQUA-HOT COMPONENTS
DC High-Limit Thermostat: Left
The left DC high-limit thermostats serve as a safety measure
in the event that the Propane-Burner continues to operate
after the maximum operating temperature is reached. The
high-limit thermostats allow the current for the PropaneBurner to pass through them until the boiler tank reaches a
temperature of 215°F. Should this temperature be reached,
the left high-limit thermostat will trip, which will prevent the
Propane-Burner from operating.
Troubleshoot the Left DC high-limit thermostat if the following condition has occurred:

The Propane-Burner fails to operate.
NOTE: If the high limit thermostat is tripped, it is recommended to test both the A.C. and D.C. control thermostats
for proper operation.
Replacement Procedure:
FAILURE TO DISCONNECT ALL POWER SUPPLIES AND/OR
TO ALLOW THE HEATER TO COOL BEFORE SERVICING
COULD CAUSE SERIOUS DAMAGE OR PERSONAL INJURY.
1.
Ensure that the Aqua-Hot has been completely shut
down and that all power sources have been
disconnected.
2.
Remove the two wires from the defective high-limit
thermostat by pulling firmly on the wires.
3.
Using a 5/8 wrench or socket, remove the defective high
-limit thermostat from the Aqua-Hot’s boiler tank.
4.
Install the replacement high-limit thermostat into the
port on the Aqua-Hot’s boiler tank and finger-tighten
only (15 in/lbs). Do Not Over-Tighten
Troubleshooting:
1.
Disconnect all power supplies.
2.
Verify that the boiler tank’s temperature is below 215°F.
3.
Locate the Left DC high-limit thermostat and remove its
wires. Reference Figure 14 for location
4.
Using a digital volt meter, set to check continuity, check
the thermostat for continuity.
5.
Connect the wires removed from the defective high-limit
thermostat to the replacement high-limit thermostat.
If there is no continuity, press the white reset button on
the thermostat and re-check for continuity.
6.
Test for proper operation.
If continuity is still not present after the reset button has
been pressed, follow the instructions in this section to
replace the Left DC high-limit thermostat.
Figure 14
215° D.C. High Limit Thermostats
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 28 —
SECTION 4: AQUA-HOT COMPONENTS
DC High-Limit Thermostat: Right
The DC high-limit thermostats serve as a safety measure in
the event that the Propane-Burner continues to operate after
the maximum operating temperature is reached. The highlimit thermostats allow the current for the Propane-Burner to
pass through them until the boiler tank reaches a temperature
of 215°F. Should this temperature be reached, the right highlimit thermostat tells the control board that the fan has
stopped and it goes into a shutdown sequence and possible
lockdown for an hour.
Troubleshoot the right DC high-limit thermostat if the following condition has occurred:


Propane-Burner fails to operate.
If the Combustion Blower Fan fails to operate.
Troubleshooting:
NOTE: If the high limit thermostat is tripped, it is recommended to test both the A.C. and D.C. control thermostats
for proper operation.
Replacement Procedure:
FAILURE TO DISCONNECT ALL POWER SUPPLIES AND/OR
TO ALLOW THE HEATER TO COOL BEFORE SERVICING
COULD CAUSE SERIOUS DAMAGE OR PERSONAL INJURY.
1.
Ensure that the Aqua-Hot has been completely shut
down and that all power sources have been disconnected.
2.
Remove the two wires from the defective high-limit
thermostat by pulling firmly on the wires.
3.
Using a 5/8 wrench or socket, remove the defective high
-limit thermostat from the Aqua-Hot’s boiler tank.
4.
Install the replacement high-limit thermostat into the
port on the Aqua-Hot’s boiler tank and finger-tighten
only (15 in/lbs).
1.
Disconnect all power supplies.
2.
Verify that the boiler tank’s temperature is below 215°F.
3.
Locate the Right DC high-limit thermostat and remove
its wires. Reference Figure 15 for location
5.
Connect the wires removed from the defective high-limit
thermostat to the replacement high-limit thermostat.
4.
Using a digital volt meter, set to check continuity, check
the thermostat for continuity.
6.
Test for proper operation.
If there is no continuity, press the white reset button on
the thermostat and re-check for continuity.
If continuity is still not present after the reset button has
been pressed, follow the instructions in this section to
replace the Right DC high-limit thermostat.
Figure 15
215° D.C. High Limit Thermostats
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 29 —
SECTION 4: AQUA-HOT COMPONENTS
Low-Temperature Cut-off Thermostat:
(For heaters manufactured before Serial Number A375-10060)
The low-temperature cut-off thermostat operates the domestic water priority system by blocking the interior heating
feature when domestic hot water is being used. This ensures
that even heat is provided for domestic hot water, which
avoids the possibility of cold water pockets during showers.
If the Heater works properly with the thermostat bypassed,
follow the instructions in this section to replace the lowtemperature cutoff thermostat.
Lack of Hot Water
1.
If the “Low Temp Cutoff Thermostat” Does not trip when
domestic hot water is being used or when the Aqua-Hot
falls below operating temperature, complete the following:
NOTE: The Low Temperature Cut-Off thermostat disables
the interior heating zone fans, only.
A. Using a temperature sensor, verify that the lowtemperature cutoff thermostat is below 90°F, which is
necessary for the thermostat to trip.
Troubleshoot the low-temperature cut-off thermostat if the
following conditions have occurred:
B. Inspect the wiring to ensure that the Aqua-Hot is
wired properly and that the low-temperature cutoff
thermostat has not been bypassed via jumper wires.


There is a lack of interior heat.
There is a lack of hot water .
2.
Troubleshooting:
Lack of Interior Heat
1.
C. Ensure the Domestic water lines have been plumbed
properly into and out of the heater.
Determine if the conditions are right for the “Low Temp
Cut-off Thermostat to be reset
A. Verify that the Aqua-Hot is at operating temperature
- between 158°F and 190°F.
B. Verify that the domestic hot water is not being used.
Disconnect the Low Temperature Cut-Off thermostat’s
wires from the Aqua-Hot’s wiring harness, and test for
proper operation.
A. If the Heater makes good hot water with the Low
Temperature Cut-Off Thermostat disconnected,
replace the Low Temperature Cut off Thermostat.
NOTE: It is recommended to test the cold water coming
into the heater, before replacing the Low Temperature CutOff thermostat. Warm fresh water being supplied to the
heater will result in the Low Temperature Cut-off thermostat
not tripping.
If the “Low Temp Cutoff ” thermostat is not reset (i.e.
has continuity) after it has been determined that it
should be reset, complete the following:
A.
Using a temperature sensor, verify that the lowtemperature cutoff thermostat is above 100°F.
If the thermostat is below 90°F, verify that the Aqua
-Hot is up to operating temperature and that a hot
water faucet is not leaking.
B. Disconnect the low-temperature cut-off thermostat’s
wires from the Aqua-Hot’s wiring harness, then,
jump the wiring harness wires for the thermostat
together to bypass the thermostat. Wires 23 &24.
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 30 —
SECTION 4: AQUA-HOT COMPONENTS
Low-Temperature Cut-off Thermostat:
(For heaters manufactured before Serial Number A375-10060)
NOTE: The Low Temperature Cut-Off thermostat disables the interior heating zone fans and the heating zone
pumps.
The low-temperature cut-off thermostat operates the domestic water priority system by blocking the interior heating
feature when domestic hot water is being used. This ensures
that even heat is provided for domestic hot water, which
avoids the possibility of cold water pockets during showers.
Troubleshoot the low-temperature cut-off thermostat if the
following conditions have occurred:

There is a lack of interior heat.

There is a lack of hot water .
If the Heater works properly with the thermostat bypassed,
follow the instructions in this section to replace the lowtemperature cutoff thermostat.
Lack of Hot Water
1.
A. Using a temperature sensor, verify that the lowtemperature cutoff thermostat is below 90°F, which is
necessary for the thermostat to trip.
B. Inspect the wiring to ensure that the Aqua-Hot is
wired properly and that the low-temperature cutoff
thermostat has not been bypassed via jumper wires.
C. Ensure the Domestic water lines have been plumbed
properly into and out of the heater.
Troubleshooting:
Lack of Interior Heat
1.
2.
Determine if the conditions are right for the “Low Temp
Cut-off Thermostat to be reset
B. Verify that the domestic hot water is not being used.
If the “Low Temp Cutoff ” thermostat is not reset (i.e.
has continuity) after it has been determined that it
should be reset, complete the following:
Using a temperature sensor, verify that the lowtemperature cutoff thermostat is above 100°F.
If the thermostat is below 90°F, verify that the Aqua
-Hot is up to operating temperature and that a hot
water faucet is not leaking.
B. Disconnect the low-temperature cut-off thermostat’s
wires from the Aqua-Hot’s wiring harness, then,
jump the wiring harness wires for the thermostat
together to bypass the thermostat. Wires 23 &24.
Disconnect the Low Temperature Cut-Off thermostat’s
wires from the Aqua-Hot’s wiring harness, and test for
proper operation.
A. If the Heater makes good hot water with the Low
Temperature Cut-Off Thermostat disconnected,
replace the Low Temperature Cut off Thermostat.
A. Verify that the Aqua-Hot is at operating temperature
- between 158°F and 190°F.
A.
If the “Low Temp Cutoff Thermostat” Does not trip when
domestic hot water is being used or when the Aqua-Hot
falls below operating temperature, complete the following:
NOTE: It is recommended to test the cold water coming
into the heater, before replacing the Low Temperature CutOff thermostat. Warm fresh water being supplied to the
heater will result in the Low Temperature Cut-off thermostat
not tripping.
Replacement Procedure:
FAILURE TO DISCONNECT ALL POWER SUPPLIES AND/OR TO
ALLOW THE HEATER TO COOL BEFORE SERVICING COULD
CAUSE SERIOUS DAMAGE OR PERSONAL INJURY.
1. Ensure that the Aqua-Hot has been completely shut down
and that all power sources have been
disconnected.
2.
Locate the low-temperature cut-off thermostat on the cold
domestic water inlet pipe on the Aqua-Hot.
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 31 —
SECTION 4: AQUA-HOT COMPONENTS
3.
Disconnect the defective low-temperature cut-off thermostat’s wires by separating the quick-disconnect terminals.
4.
Using a 5/8 wrench or socket, remove the defective lowtemperature cut-off thermostat from the Aqua-Hot.
5.
Install the replacement low-temperature cut-off thermostat tightening only to 15 in/lbs. Do not overtighten.
6.
Connect the replacement low-temperature cut-off thermostat’s wires in the same configuration as the removed
thermostat’s wires.
7.
Test for proper operation.
Figure 16
Low Temperature Cutoff
Thermostat
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 32 —
SECTION 4: AQUA-HOT COMPONENTS
Valves
Interior Zone Check Valve:
Replacement Procedure:
FAILURE TO DISCONNECT ALL POWER SUPPLIES AND/OR
TO ALLOW THE HEATER TO COOL BEFORE SERVICING
Check valves are installed into the zone outlet ports for each
heating loop to ensure that the antifreeze and water heating
solution only flows in one direction. If the heating solution
attempts to backflow into the boiler tank, the check valve
closes to prevent that from happening.
COULD CAUSE SERIOUS DAMAGE OR PERSONAL INJURY.
1.
Ensure that the Aqua-Hot has been completely shut
down and that all power sources have been disconnected. Also, because this replacement procedure will involve the boiler tank and the potential for hot coolant, be
sure the heater has adequately cooled.
2.
Drain the antifreeze and water heating solution from the
Aqua-Hot’s boiler tank using the drain valve.
3.
Remove the Check Valve Access cover, on the side of
the Aqua-Hot.
4.
Using constant tension pliers, loosen and slide back the
constant tension clamps securing the hoses to the defective check valve.
5.
Remove the hoses from the defective check valve.
6.
Remove both the 90* hose barb and the straight hose
barb fittings from the defective check valve.
7.
Clean the 90* hose barb and straight hose barb fittings,
then wrap the 90* hose barb and the straight hose barb
threads with a thread seal tape.
8.
Install the 90* hose barb and straight hose barb fittings
on the replacement check valve, ensuring that they are
installed properly with the 90* hose barb on the arrow
side of the check valve. Reference Figure 17.
9.
Install the replacement check valve onto the Aqua-Hot’s
boiler tank. The arrow on the check valve must point
towards the back of the boiler tank.
Troubleshoot the check valves if the following condition has
occurred:

The zone pump and fans are operating, but there is still a
lack of interior heat in a particular zone.
Troubleshooting:
1.
Verify that the heating zone is operating properly by
checking the following:
A. Check the Room Thermostat, to ensure it is calling
for heat.
B. Check the circulation pump for operation by visually inspecting it for rotation of the pump.
2.
With the circulation pump operating, tap on the check
valve and wait five minutes to evaluate if interior heat is
now present.
If interior heat is present after tapping on the check
valve, the check valve was stuck closed .
3.
Check the Aqua-Hot’s antifreeze and water heating solution’s ratio of water to propylene glycol. The mixture
ratio should be approximately 50/50. If the solution is
comprised fully of antifreeze (100%), the check valves
will continue to stick.
NOTE: Storing the motor home for an extended period of
time can cause the check valves to stick. If, after the initial
release of the stuck check valve, it continues to stick, or if it
never releases follow the instructions in this section to
replace the check valve.
10. Slide the hoses back onto the replacement check valve
and set the constant tension clamp back into place.
11. Refill the Aqua-Hot’s boiler tank with the antifreeze and
water heating solution. Reference Section 5.
12. Test for proper operation.
13. Reinstall the Check Valve Access Cover.
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 33 —
SECTION 4: AQUA-HOT COMPONENTS
Figure 17
Check Valve Assembly
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 34 —
SECTION 4: AQUA-HOT COMPONENTS
Tempering Valve:
5.
Remove the Tempering Valve Assembly from the AquaHot.
A. Disconnect the hot and cold water lines, located on
the front of the Aqua-Hot boiler tank.
B. Loosen the retaining nut on the Hot Water Bulkhead
fitting.
C. Remove the Tempering Valve Assembly, by
lowering the assembly and pulling it out the front of
the Aqua-Hot.
6.
Remove the brass fittings from the defective Tempering
valve.
The tempering valve for the Aqua-Hot mixes the heated domestic water from the boiler tank with cold domestic water at
a preset ratio to reduce the risk of scalding.
Troubleshoot the tempering valve if the following condition
has occurred:


There is a lack of hot domestic water.
The Domestic hot water is too hot.
Troubleshooting:
1.
Inspect the tempering valve to ensure that it has not been
leaking.
7.
Clean and wrap the threads on the brass fittings with a
thread seal tape.
2.
Test the tempering valve’s functionality by turning the
knob. If the tempering valve’s knob does not turn
freely, follow the instructions in this section to replace
the tempering valve.
8.
Install the brass fittings onto the replacement tempering
valve.
9.
Re-Install the tempering valve Assembly onto the AquaHot.
3.
Test the temperature of the hot water using a digital
thermometer at one of the hot water faucets. Water
Temperature should range between 115° F - 123° F. If
the proper range cannot be set follow the instructions in
this section to replace the tempering valve.
Replacement Procedure:
FAILURE TO DISCONNECT ALL POWER SUPPLIES AND/OR
TO ALLOW THE HEATER TO COOL BEFORE SERVICING
COULD CAUSE SERIOUS DAMAGE OR PERSONAL INJURY.
1.
Turn the motor home’s water pump off.
2.
Locate and remove the Domestic Water Access Panel
3.
Drain the water pressure by opening the faucets and allowing the water to drain.
4.
10. Reconnect the hot and cold water lines onto the hot and
cold pipes, located on the front of the Aqua-Hot boiler
tank.
11. Re-Install the retaining nut on the Hot Water Bulkhead
fitting.
12. Reconnect the motor home’s water lines to the tempering valve assembly, ensuring they are plumbed correctly.
13. Turn the motor home’s water pump back on and check
for leaks and the presence of hot domestic water.
14. Verify that the replacement tempering valve has been set
to the proper setting by taking a digital thermometer to
a hot water faucet and set the water temperature between
115*F - 123*F.
15. Re-Install the Domestic Water Access Panel
Disconnect the motor home’s water lines from the tempering valve assembly, on top of the Aqua-Hot.
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
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SECTION 4: AQUA-HOT COMPONENTS
Figure 18
Bulk Head Fitting
Retaining Nut
Front of Heater
Hot Water
Outlet Port
Cold Water
Inlet Port
Mixer Valve Assembly
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
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SECTION 4: AQUA-HOT COMPONENTS
Pumps - Manufactured before serial number
Replacement Procedure:
A375-110060
FAILURE TO DISCONNECT ALL POWER SUPPLIES AND/OR TO
Zone Pumps #1 and #2:
The Zone pumps first draw the heated antifreeze and water
heating solution from the Aqua-Hot’s boiler tank, then propel it through the Hydronic heating system’s interior heat
plumbing.
ALLOW THE HEATER TO COOL BEFORE SERVICING COULD CAUSE
SERIOUS DAMAGE OR PERSONAL INJURY
1.
Ensure that the Aqua-Hot has been completely shut down and
that all power sources have been disconnected. Also, because
this replacement procedure will involve the potential for hot
coolant, be sure the heater has adequately cooled.
Troubleshoot the Zone pumps if the following condition has
occurred:
2.
Drain the antifreeze and water heating solution from the AquaHot’s boiler tank using the drain valve.


3.
Release the pump from the mounting bracket by inserting an
Awl between the locking teeth and gently prying the locking
teeth apart. Then remove the defective pump from the bracket
mounted to the Aqua-Hot.
4.
Disconnect the defective pump’s wires by pulling out on the
“Red Locking Tab” on the harness plug, and separating the
harness plug from the defective pump.
The Zone pump is not operating.
There is a lack of heat in the coach.
NOTE: Reference the wiring Schematic for heaters manufactured before 09/2011.in Appendix A.
Troubleshooting:
1. Turn on the interior room thermostat corresponding to the
Zone pump not operating.
A. Using a Volt Meter , Check for voltage on the Fuse
Block for the zone pumps, #56(WHT).
a. If No voltage, replace the fuse.
b. If Yes continue.
NOTE: Not all harnesses have the “Red Locking Tab”. If the
harness does not have the “Red Locking Tab”, the harness can be
separated by simply pulling the plug out of the pump.
B. Using a Volt Meter, Check and ensure that the zone
relay is sending voltage to the pump at pin 4.
a. If No voltage is present troubleshoot the
zone relay.
b. If Yes continue.
5.
Using constant tension pliers, loosen and slide back the constant tension clamps securing the hoses to the zone pump.
6.
Remove the hoses from the defective zone pump.
7.
Slide the hoses back onto the replacement zone pump and set
the constant tension clamps back into place.
8.
Reconnect the harness plug into the replacement pump. Be
sure to push in on the red locking tab, to secure the plug to the
replacement pump.
C. Check the Zone pump for voltage.
a. If there is voltage and the zone pump is not
operating, follow the zone pump replacement procedure in this book.
NOTE: The zone pump can be tested by connecting it to an
external 12 Volt-DC power source to verify that the pump is
defective.
9. Install the replacement pump onto the mounting bracket, and
squeeze the pump bracket together with a pair of channel lock
pliers, to secure the pump.
10. Refill the Aqua-Hot’s boiler tank with the antifreeze and water
heating solution. Reference Section 5 for filling instructions.
11. Test the Aqua-Hot for normal operation.
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
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SECTION 4: AQUA-HOT COMPONENTS
Pumps - Manufactured starting with serial
Replacement Procedure:
number A375-110060
Zone Pumps #1 and #2:
The Zone pumps first draw the heated antifreeze and water
heating solution from the Aqua-Hot’s boiler tank, then propel it through the Hydronic heating system’s interior heat
plumbing.
Troubleshoot the Zone pumps if the following condition has
occurred:


The Zone pump is not operating.
There is a lack of heat in the coach.
FAILURE TO DISCONNECT ALL POWER SUPPLIES AND/OR TO
ALLOW THE HEATER TO COOL BEFORE SERVICING COULD CAUSE
SERIOUS DAMAGE OR PERSONAL INJURY
1.
Ensure that the Aqua-Hot has been completely shut down and
that all power sources have been disconnected. Also, because
this replacement procedure will involve the potential for hot
coolant, be sure the heater has adequately cooled.
2.
Drain the antifreeze and water heating solution from the AquaHot’s boiler tank using the drain valve.
3.
Release the pump from the mounting bracket by inserting an
Awl between the locking teeth and gently prying the locking
teeth apart. Then remove the defective pump from the bracket
mounted to the Aqua-Hot.
4.
Disconnect the defective pump’s wires by pulling out on the
“Red Locking Tab” on the harness plug, and separating the
harness plug from the defective pump.
NOTE: Reference the wiring Schematic for heaters manufactured after 09/2011, in Appendix A.
Troubleshooting:
1. Turn on the interior room thermostat corresponding to the
NOTE: On heaters manufactured after 09/2011 the Low
Temp Cut Off Thermostat will shut down the pumps if hot
water is being used. Therefore, Before troubleshooting the
heating zone circulation pumps verify the Low Temp CutOff thermostat has continuity.
Zone pump not operating.
A. Using a Volt Meter , Check for voltage on the Fuse
Block for the zone pumps, #58(ORG).
a. If No voltage, replace the fuse.
b. If Yes continue.
B. Using a Volt Meter, Check and ensure that the zone
relay is sending voltage to the pump at pin 4.
a. If No voltage is present troubleshoot the
zone relay.
b. If Yes continue.
C. Check the Zone pump for voltage.
a. If there is voltage and the zone pump is not
operating, follow the zone pump replacement procedure in this book.
NOTE: The zone pump can be tested by connecting it to an
external 12 Volt-DC power source to verify that the pump is
Defective.
NOTE: Not all harnesses have the “Red Locking Tab”. If the
harness does not have the “Red Locking Tab”, the harness can be
separated by simply pulling the plug out of the pump.
5.
Using constant tension pliers, loosen and slide back the constant tension clamps securing the hoses to the zone pump.
6.
Remove the hoses from the defective zone pump.
7.
Slide the hoses back onto the replacement zone pump and set
the constant tension clamps back into place.
8.
Reconnect the harness plug into the replacement pump. Be
sure to push in on the red locking tab, to secure the plug to the
replacement pump.
9. Install the replacement pump onto the mounting bracket, and
squeeze the pump bracket together with a pair of channel lock
pliers, to secure the pump.
10. Refill the Aqua-Hot’s boiler tank with the antifreeze and water
heating solution. Reference Section 5 for filling instructions.
11. Test the Aqua-Hot for normal operation.
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
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SECTION 4: AQUA-HOT COMPONENTS
Awl Inserted into
the mounting
bracket
Figure 19
Zone Pump 1
Zone Pump 2
Harness Plug
with
Red Locking Tab
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
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SECTION 4: AQUA-HOT COMPONENTS
Figure 20
Zone Pump 2/Stir Pump
If Propane-Burner combustion blower fan is running,
and no voltage is present at the #45 wire, check Combustion Blower Fan Buck Boost for power at the red
#93 wire. If no power is present Trouble shoot the
Combustion Blower Fan Buck Boost.
Stir Pump (Zone Pump #2):
The stir pump circulates the antifreeze and water heating
solution within the Aqua-Hot’s boiler tank in order to ensure
even-heating of the solution. To accomplish this, the stir
pump draws the solution from the bottom of the tank and
deposits it back into the top of the tank, after circulation
through Heating Loop #2.
B. Using a Volt Meter check the zone 2 relay for
voltage on the #4 pin.
If there is no voltage at zone 2 relay, check
wire #45 for damage.
Troubleshoot the stir pump if the following condition has
occurred:

C. Using a Volt Meter check the #2 zone pump for
voltage.
There is a lack of hot domestic water.
Troubleshooting:
If voltage is present and the pump still fails to operate follow the circulation pump replacement
procedure in this book.
NOTE: In order for the stir pump to operate, the Propane
burner combustion blower fan must be running.
3.
If it is determined that the pump is active, verify that the
pump is operating properly by checking both connected
hoses for heat.
1.
Verify that the Propane Burner combustion blower fan is
running.
2.
If the Propane burner combustion blower fan is running
and the stir pump still is not operating:
If both hoses are hot, the pump is working properly.
A. Using a Volt Meter, test for dc voltage at the
Propane burner electronic controller, at the #45 red
wire.
If one hose is hot, or neither hose is hot:
1. check the cold hose for a blockage.
2. Trouble Shoot the Zone Check Valve
If no blockage exists on either hose, and it is determined the check valve is not stuck: follow the instructions in this section to replace the Zone pump #2.
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
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SECTION 4: AQUA-HOT COMPONENTS
Electrical - AC
If the Electric Switch is on, and operating properly:
A. Check the temperature of the Aqua-Hot’s boiler
tank.
Electric Heating Element:
The electric heating element uses AC power as an alternate
power source for heating the Aqua-Hot’s boiler tank.
If the boiler tank temperature is below 158°F, Verify that the control thermostat for the electric element is operating properly.
Troubleshoot the electric heating element if the following
condition has occurred:

There is a lack of hot domestic water and interior heat
when the electric element is selected as the heating
source.
Troubleshooting:
If the boiler tank is above 185°F, the Aqua-Hot is at
operating temperature and requires no heat.
4.
Check functionality of the A.C. Relay. Refer to A.C.
Relay troubleshooting, in this section.
5.
Verify that the electric heating element is receiving adequate AC power by completing the following:
NOTE: For continuous domestic hot water to be present,
the Propane-Burner must be selected also as a heating
source.
1.
2.
3.
A. Remove the AC access cover.
B. Using an AC voltmeter, verify that 110 volts of AC
power are present.
Verify that the motor home is either plugged into shore
power or that the generator is running to provide AC
power.
Verify that the “Electric” Switch is in the ON position,
on the interior switch panel inside the motor home.
C. Using a digital clamp on amp-meter, verify that
11.2 to 13 amps are present at the element’s wires.
NOTE: If there is 11.2 to 13 amps of A.C. Current present
the electric element is operating properly.
Using a Volt Meter, Verify the presence of 12vdc
voltage at the terminal block on both the AI (power in
from the switch) and AO (power out to the switch) pins.
D. Disconnect the coach from shore power/turn off
generator and Check the electric element’s wires for
continuity by completing the following:
If there is no 12VDC voltage present, complete the following:
A. Verify that the electric element switch on the interior switch panel is on.
B. Verify that the heater is full of antifreeze. If the
heater is full of antifreeze, verify the Float Switch is
functioning properly.
C. Install a jumper wire on the terminal block, between
the AI and AO pins to bypass the electric element
switch.
If the “Electric Heating Element ” works with the jumper wire installed, replace the Electric Switch, on the interior switch panel.
5.
a.
Disconnect the wires from the electric heating
element.
b.
Disconnect the wires from the AC terminal
block.
c.
Check the black and white wires, individually,
for continuity.
Check the electric heating element for functionality by
completing the following:
A. Disconnect all power supplies.
B. Remove all wires from the electric heating element.
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
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SECTION 4: AQUA-HOT COMPONENTS
C. Using a digital volt meter, set to register ohms, check
the electric heating element for the proper ohms, reading of 10 - 11 Ohms
5.
Using a 7/8 inch socket, remove the defective electric heating element from the Aqua-Hot’s boiler tank.
6.
Wrap the new electric element threads with a thread seal
tape.
7.
Install the replacement 1500-watt electric heating element
into the boiler tank, and securely tighten .
8.
Connect the wires removed from the defective electric
heating element to the replacement electric heating element utilizing crimp terminals.
9.
Reinstall the propane burner. Reference Section 7.
If the proper ohms do not exist follow the instructions
in this section to replace the electric heating element.
Replacement Procedure:
FAILURE TO DISCONNECT ALL POWER SUPPLIES AND/OR TO
ALLOW THE HEATER TO COOL BEFORE SERVICING COULD
CAUSE SERIOUS DAMAGE OR PERSONAL INJURY.
1.
2.
Ensure that the Aqua-Hot has been completely shut down
and that all power sources have been disconnected. Also,
because this replacement procedure will involve the boiler
tank and the potential for hot coolant, be sure the heater
has adequately cooled.
10. Refill the Aqua-Hot’s boiler tank with the antifreeze
and water heating solution. Reference Section 5.
11. Test for proper operation.
Drain the antifreeze and water heating solution from the
Aqua-Hot’s boiler tank using the drain valve.
3. Remove the Propane-Burner. Reference Section 7.
4.
Remove the two wires secured to the defective electric
heating element by cutting them with wire cutters.
Figure 21
1500 Watt Electric Element
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
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SECTION 4: AQUA-HOT COMPONENTS
AC Relay:
The AC relay is an electrical device where the DC circuit
from the electric switch determines whether the AC power is
permitted to flow to the electric heating element. This allows the 12 VDC electric switch to switch the 120 VAC
electric heating element on and off in conjunction with the
interior switch panel and control thermostat even though the
electric heating element is on a separate circuit.
Troubleshoot the AC relay if the following condition has
occurred:

6. Locate the VAC relay.
A. Check pins 1 & 0 for 12 VDC power and ground.
1. Pin 1 is - and Pin 0 is +.
If there is no 12VDC + and - present:
1. check wires for damage or loose
connections.
2. Follow the instructions in this manual for
trouble shoot the Electric element Control
thermostat.
The electric heating element fails to operate.
FAILURE TO DISCONNECT ALL POWER SUPPLIES AND/OR
Troubleshooting:
1.
2.
3.
4.
TO ALLOW THE HEATER TO COOL BEFORE SERVICING
Disconnect the AC power source to the motor home
(unplugging from shore power or shutting off the generator).
Turn the electric element switch on the interior switch
panel to the ON position.
Verify the Following:
A. The Electric Element Switch is operating properly
B. The Control Thermostat is Calling for heat.
C. The Float Switch is functioning properly.
Using a voltmeter, check pin AI on the terminal block
for 12 Volts-DC. If no voltage is present:
A. Check the B fuse on fuse block, for power. If no
power is present check fuse.
B. If fuse is good, follow the troubleshooting guide for
the float switch.
5.
COULD CAUSE SERIOUS DAMAGE OR PERSONAL INJURY.
B. Ensure that all the A.C. power supplies to the coach
have been disconnected.
1.
Turn the electric switch to the on position and
Verify it is sending 12VDC power to the A.C.
relay.
2.
Locate the AC wires connected to the AC relay
(pins 4 and 2), and remove the AC wires from
the relay.
3.
Using an ohmmeter, check the relay AC pins
(4 and 2) for continuity.
If no continuity exists, follow the instructions in this
section to replace the AC relay.
Using a Voltmeter check pin A0, on terminal block, for
power.
A. If no power is present follow troubleshooting
guide for the electric element switch.
B. If 12 Volts of DC power are present, continue:
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
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SECTION 4: AQUA-HOT COMPONENTS
AC Relay:
Replacement Procedure:
FAILURE TO DISCONNECT ALL POWER SUPPLIES AND/OR
TO ALLOW THE HEATER TO COOL BEFORE SERVICING
COULD CAUSE SERIUOS DAMAGE OR PERSONAL INJURY.
1.
Ensure that the Aqua-Hot has been completely shut
down and that all power sources have been disconnected.
2.
Also, ensure that the motor home is not connected to
shore power and that a generator is not running during
this replacement procedure.
3.
Locate the A.C. Relay on side of unit, Reference Figure
22 for location of A.C. Relay.
4.
Release the wires from the defective A.C. relay by removing the corresponding screw terminals.
5. Remove A.C. Relay from the side of the heater.
6.
Attach the replacement A.C. relay to the side of heater.
7.
Using the wiring diagram in Appendix A, connect the
wires previously removed, to the replacement AC relay.
8.
Test for proper operation.
NOTE: The motor home must be plugged into shore
power or the generator must be running for the electric
element to be operational.
Figure 22
A.C. Relay
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
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SECTION 4: AQUA-HOT COMPONENTS
Zone Relay: Interior Heat Exchanger Fans
For heaters manufactured before serial number
A375-110060
The Zone relay is an electrical device where the DC circuit
from the Interior Room Thermostat determines whether the
DC power is permitted to flow to the circulation pump and
the heat exchanger fans. This allows the Interior Room
Thermostat to switch both the fans and circulation pump on.
Troubleshoot the Zone relay if either of the following conditions have occurred:


The Interior fans fail to operate.
The circulation pump fails to operate
Troubleshooting:
If the Interior
1.
2.
heat exchanger Fans fail to operate:
Turn the corresponding room thermostat on, on the interior of the motor home, ensuring the thermostat is set at
the maximum heat setting, to ensure they will call for
heat.
Since the Aqua-Hot 375-LP is a hot water priority system, make sure the Low Temperature cut-off Thermostat
is not tripped, by Making sure the heater is up to operating temperature, and that domestic hot water is NOT
being used. Reference the Low Temperature Cut-off
thermostat troubleshooting in this section.
3. Locate the Fuse block, and using a volt meter, check for
12VDC on the C Fuse.
If no power is present check fuse.
4. On the zone relay, check pin 6 for 12 VDC +.
If no power is present inspect wire #24 for damage.
5. On the Zone relay check pin 1 for 12 VDC +
If no power is present check E fuse
6. On the Zone Relay check pin 0 for ground.
If there is not a ground present, verify that the room
thermostat is calling for heat, and that it is sending a
ground signal to the relay.
NOTE: If there is no ground for pin 0, it is possible to bypass the motor homes’ interior room thermostat by supplying an external ground to the terminal block for the particular zone being trouble shot. If the zone works with the interior room thermostat bypassed the problem is located in the
motor home, not within the heating system.
5. On the zone relay, check pin #8 for 12 VDC +.
If no voltage is present follow the replacement
procedure for the zone relay in this section.
Figure 23a
Zone Relay
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
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SECTION 4: AQUA-HOT COMPONENTS
Zone Relay: Interior Heat Exchanger Fans
For heaters manufactured starting with serial
number A375-110060
The Zone relay is an electrical device where the DC circuit
from the Interior Room Thermostat determines whether the
DC power is permitted to flow to the circulation pump and
the heat exchanger fans. This allows the Interior Room
Thermostat to switch both the fans and circulation pump on.
Troubleshoot the Zone relay if either of the following conditions have occurred:


The Interior fans fail to operate.
The circulation pump fails to operate
Troubleshooting:
If the Interior
1.
2.
heat exchanger Fans fail to operate:
Turn the corresponding room thermostat on, on the interior of the motor home, ensuring the thermostat is set at
the maximum heat setting, to ensure they will call for
heat.
Since the Aqua-Hot 375-LP is a hot water priority system, make sure the Low Temperature cut-off Thermostat
is not tripped, by Making sure the heater is up to operating temperature, and that domestic hot water is NOT
being used. Reference the Low Temperature Cut-off
thermostat troubleshooting in this section.
3. Locate the Fuse block, and using a volt meter, check for
12VDC on the C Fuse.
A. If no power is present check fuse.
4. On the zone relay, check pin 1 for 12 VDC +.
A. If no power is present inspect wire #24 for damage.
B. Verify the LTCO has continuity
5. On the Zone relay check pin 6 for 12 VDC +
If no power is present check E fuse
6. On the Zone Relay check pin 0 for ground.
If there is not a ground present, verify that the room
thermostat is calling for heat, and that it is sending a
ground signal to the relay.
NOTE: If there is no ground for pin 0, it is possible to bypass the motor homes’ interior room thermostat by supplying an external ground to the terminal block for the particular zone being trouble shot. If the zone works with the interior room thermostat bypassed the problem is located in the
motor home, not within the heating system.
5. On the zone relay, check pin #8 for 12 VDC +.
If no voltage is present follow the replacement
procedure for the zone relay in this section.
Figure 23b
Zone Relay
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
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SECTION 4: AQUA-HOT COMPONENTS
Zone Relay: - Circulation Pump
For heaters manufactured before serial number
A375-110060
The Zone relay is an electrical device where the DC circuit
from the Interior Room Thermostat determines whether the
DC power is permitted to flow to the circulation pump and
the heat exchanger fans. This allows the Interior Room
Thermostat to switch both the fans and circulation pump on.
Troubleshoot the Zone relay if either of the following conditions have occurred:


The Interior fans fail to operate.
The circulation pump fails to operate
Troubleshooting:
If the Circulation
1.
Pump Fails to operate:
Turn the corresponding room thermostat on, on the interior of the motor home, ensuring the thermostat is set at
the maximum heat setting, to ensure they will call for
heat.
NOTE: Even though the Aqua-Hot 375 is a Hot Water Priority system, and utilizes a Low Temperature Cut-Off thermostat to shut the heat exchanger fans off, on the inside of
the motor home, this function does not shut down the circulation pumps. It only shuts the interior heat exchanger fans
off, and therefore will not cause the pumps to not operate.
2. Locate the Fuse block, and using a volt meter, check for
12VDC on the D Fuse.
If no power is present check fuse.
3. On the zone relay, check pin 2 for 12 VDC +.
If no power is present inspect wire #58/#59 for
damage.
4. On the Zone relay check pin 1 for 12 VDC +
If no power is present check E fuse
5. On the Zone Relay check pin 0 for ground.
If there is not a ground present, verify that the room
thermostat is calling for heat, and that it is sending a
ground signal to the relay.
NOTE: If there is no ground for pin 0, it is possible to bypass the motor homes’ interior room thermostat by supplying an external ground to the terminal block for the particular zone being trouble shot. If the zone works with the interior room thermostat bypassed the problem is located in the
motor home, not within the heating system.
6. On the zone relay, check pin #4 for 12 VDC +.
If no voltage is present follow the replacement
procedure for the zone relay in this section.
Figure 24a
Zone Relay
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
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SECTION 4: AQUA-HOT COMPONENTS
Zone Relay: - Circulation Pump
For heaters manufactured starting with serial
number A375-110060
The Zone relay is an electrical device where the DC circuit
from the Interior Room Thermostat determines whether the
DC power is permitted to flow to the circulation pump and
the heat exchanger fans. This allows the Interior Room
Thermostat to switch both the fans and circulation pump on.
Troubleshoot the Zone relay if either of the following conditions have occurred:


The Interior fans fail to operate.
The circulation pump fails to operate
Troubleshooting:
If the Circulation
Pump Fails to operate:
1.
Turn the corresponding room thermostat on, on the interior of the motor home, ensuring the thermostat is set at
the maximum heat setting, to ensure they will call for
heat.
2.
Since the Aqua-Hot 375-LP is a hot water priority system, make sure the Low Temperature cut-off Thermostat
is not tripped, by Making sure the heater is up to operating temperature, and that domestic hot water is NOT
being used. Reference the Low Temperature Cut-off
thermostat troubleshooting in this section.
2. Locate the Fuse block, and using a volt meter, check for
12VDC on the D Fuse.
a. If no power is present check fuse.
3. On the zone relay, check pin 2 for 12 VDC +.
a. If no power is present inspect wire #58/#59 for
damage.
4. On the Zone relay check pin 1 for 12 VDC +
a. If no power is present check C Fuse
b. Verify the LTCO has continuity
5. On the Zone Relay check pin 0 for ground.
a. If there is not a ground present, verify that the room
thermostat is calling for heat, and that it is sending a
ground signal to the relay.
NOTE: If there is no ground for pin 0, it is possible to bypass the motor homes’ interior room thermostat by supplying an external ground to the terminal block for the particular zone being trouble shot. If the zone works with the interior room thermostat bypassed the problem is located in the
motor home, not within the heating system.
6. On the zone relay, check pin #4 for 12 VDC +.
a. If no voltage is present follow the replacement
procedure for the zone relay in this section.
Figure 24b
Zone Relay
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
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SECTION 4: AQUA-HOT COMPONENTS
Zone Relay - Replacement Procedure
FAILURE TO DISCONNECT ALL POWER SUPPLIES AND/OR
TO ALLOW THE HEATER TO COOL BEFORE SERVICING
COULD CAUSE SERIUOS DAMAGE OR PERSONAL INJURY.
Ensure that the Aqua-Hot has been completely shut
down and that all power sources have been disconnected.
4. Remove the Zone Relay from the side of the heater.
5.
Attach the replacement Zone Relay to the side of heater.
2.
Locate the Zone Relay on side of unit, Reference Figure
24c for location of A.C. Relay.
6.
3.
Release the wires from the defective Zone relay by removing the corresponding screw terminals.
Using the wiring diagram in Appendix A, connect the
wires previously removed, to the replacement Zone Relay.
7.
Test for proper operation.
1.
Figure 24c
Zone Relay
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 49 —
SECTION 5: FILLING
THE
AQUA-HOT
WITH HEATING SOLUTION
Filling the Hydronic Heating System:
Only propylene glycol based “boiler” type antifreeze
deemed “GRAS” (Generally Recognized as Safe) by the
FDA shall be used in the Aqua-Hot’s Hydronic heating
system. Failure to use the above specified antifreeze type
could result in serious injury or death.
Ensure that the overflow tube is connected from the AquaHot’s expansion tank connection to the expansion tank’s
bottom connection and from the expansion tank’s top connection through the overflow tube hole in the motor home’s
bay floor prior to beginning this antifreeze and water heating
solution fill procedure. Failure to do so could result in an
antifreeze spill in the motor home’s bay. Reference Figure
30.
Figure 25
In order to provide the best freeze protection, boil-over protection, and anti-corrosion and rust protection, a 50/50 mixture of “GRAS” approved propylene glycol boiler antifreeze
and water is recommended.
Reference Section 1: Antifreeze and Water Heating Solution
for additional information regarding the antifreeze and water
heating solution. Be sure to use a “GRAS” boiler-type propylene glycol based antifreeze rather than an RV and Marine
antifreeze or an automotive antifreeze/coolant.
If assistance is needed in selecting an appropriate antifreeze,
please contact the Aqua-Hot Heating Systems Product Application Department at 1-800-685-4298.
1.
Open the Aqua-Hot’s drain valve located at the front of
the heater. Reference Figure 25.
2.
Connect a piece of 1/2 inch PEX-type tubing to the drain
valve. This piece should be long enough to transport the
antifreeze and water heating solution from its source to
the Aqua-Hot.
NOTE: It is recommended to use a pump, and pump the
antifreeze into the boiler tank, through the drain valve.
Figure 26
Drain
Valve
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 50 —
SECTION 5: FILLING
3.
4.
5.
Fill the Aqua-Hot completely with the 50/50 mixture of
antifreeze and water heating solution. This will take
approximately five gallons; look for the solution to enter
the overflow tube attached to the expansion tank connection on top of the Aqua-Hot.
When refilling, open the air-release valve located on the
expansion tank connection to release air pockets. Reference Figure 24. Hold the valve open until all air is released. Be sure the valve is closed when finished by
hand-tightening. Look for the solution to enter the overflow tube attached to the expansion tank connection on
top of the Aqua-Hot.
THE
AQUA-HOT
WITH HEATING SOLUTION
NOTE: All air is bled from the heating system when the
antifreeze solution enters the boiler tank on the inlet ports,
for the interior zone heating loops, and fluid comes out of the
expansion tank port.
8.
Once the systems have been purged, disconnect the wire
from the ground source and the terminal block.
9.
Check the Aqua-Hot’s expansion tank and top it off to
the cold level mark with the 50/50 antifreeze and water
mixture, if necessary.
10. Ensure that each thermostat’s connection wiring is still
in its original configuration. Reference Appendix A.
Close the drain valve.
Purging the System by Grounding the Zone
Thermostat Connection:
1.
Ensure that the boiler tank has been filled with the appropriate mixture of antifreeze and water heating solution.
2.
Locate Terminal Block for switches, heat exchangers,
fans and thermostats. Reference Figure 26.
3.
Locate the thermostat connection terminals T1 and T2.
Reference Figure 27.
4.
Connect a wire to the desired zone terminal to be purged
and connect the opposite end of the cable to a ground
source. Reference Figure 27.
NOTE: The circulation pump will activate as soon as the
terminal is connected to a ground source; therefore,
disconnect the wire from the ground source during the
antifreeze and water heating solution filling procedure.
5.
Allow the circulation pump to operate for approximately
1-3 minutes in order to purge the corresponding heating
loop, then remove the wire from the ground source.
6.
Open the drain valve and completely fill the Aqua-Hot’s
boiler tank with additional antifreeze and water heating
solution.
7.
Repeat steps 5 and 6 for both heating loops until all air
has been completely bled from the entire heating system.
— Page 51 —
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 51 —
SECTION 5: FILLING
THE
AQUA-HOT
WITH HEATING SOLUTION
Figure 27
Terminal Block
for Switches,
Heat Exchanger
Fans and
Thermostats
Figure 28
Zone 1 Thermostat Connection Terminal
Zone 2 Thermostat Connection Terminal
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 52 —
SECTION 5: DRAINING
THE
AQUA-HOT
WITH HEATING SOLUTION
TO DRAIN THE AQUA-HOT
Only propylene glycol based “boiler” type antifreeze
deemed “GRAS” (Generally Recognized as Safe) by the
FDA shall be used in the Aqua-Hot’s Hydronic heating
system. Failure to use the above specified antifreeze type
could result in serious injury or death.
Ensure that the overflow tube is connected from the AquaHot’s expansion tank connection to the expansion tank’s
bottom connection and from the expansion tank’s top connection through the overflow tube hole in the motor home’s
bay floor prior to beginning this antifreeze and water heating
solution fill procedure. Failure to do so could result in an
antifreeze spill in the motor home’s bay. Reference Figure
30.
In order to provide the best freeze protection, boil-over protection, and anti-corrosion and rust protection, a 50/50 mixture of “GRAS” approved propylene glycol boiler antifreeze
and water is recommended.
Ensure that the Aqua-Hot has been completely shut down
and that all power sources have been disconnected. Also,
because this replacement procedure will involve the boiler
tank and the potential for hot coolant, be sure the heater has
adequately cooled.
1.
Connect a piece of 1/2 inch PEX-type tubing or rubber
hose to the drain valve. This piece should be long
enough to transport the antifreeze and water heating
solution from the Aqua-hot to a bucket.
2.
Open the Aqua-Hot’s drain valve located at the front of
the heater. Reference Figure 27.
Note: The Aqua-Hot 375 holds approximately 5 gallons of the antifreeze and water heating solution.
Reference Section 1: Antifreeze and Water Heating Solution
for additional information regarding the antifreeze and water
heating solution. Be sure to use a “GRAS” boiler-type propylene glycol based antifreeze rather than an RV and Marine
antifreeze or an automotive antifreeze/coolant.
If assistance is needed in selecting an appropriate antifreeze,
please contact the Aqua-Hot Heating Systems Product Application Department at 1-800-685-4298.
Figure 29
Drain
Valve
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 53 —
SECTION 6: PROPANE-BURNER GENERAL RECOMMENDED MAINTENANCE
General Recommended Maintenance
Monthly
Figure 30
Check the Aqua-Hot’s antifreeze and water heating solution to
ensure that it is filled to the proper level. This solution level
should be checked in the Aqua-Hot’s Expansion Tank and
should only be checked when the Aqua-Hot is at maximum
operating temperature (i.e., when the Propane-Burner cycles
OFF at 190±5°F). The antifreeze and water heating solution’s
level should be at the “HOT” mark on the Expansion Tank;
reference Figure 30.
If the antifreeze and water heating solution needs replenishing,
fill the Aqua-Hot’s Expansion Tank to the “HOT” level mark.
Be sure to reference Section 1: Antifreeze and Water Heating
Solution for the proper antifreeze type and mixture. If the
antifreeze and water heating solution frequently needs replenishing, please contact the Aqua-Hot Heating Systems Technical Department at 1-800-685-4298 for assistance.
Annually
The Aqua-Hot operates on both AC and DC power. Be
sure to disconnect the 120 Volt-AC power supply prior to
cleaning or servicing. Failure to do so could result in
serious personal injury, electrical shock, or even death!
Operating the Aqua-Hot’s Propane-Burner or the 120
Volt-AC Electric Heating Element without the antifreeze
and water heating solution will cause serious damage to
the heater.
There is no recommended Annual Service for the PropaneBurner. If it fails to operate refer to the Propane-Burner
Trouble shooting section in this manual.
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 54 —
SECTION 6: PROPANE-BURNER COMPONENT OVERVIEW
Figure 31
Combustion
Fan
Dual Stage Gas
Valve
Exhaust
“High” Back
Pressure
Switch
Hot Surface
Igniter
Flame Sensor
Refractory
Igniter
Insulation
Fan
Validation
Switch
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 55 —
SECTION 6: PROPANE-BURNER COMPONENT OVERVIEW
Figure 32
Burner
Controller
Hot Surface
Igniter
Buck Boost
Combustion
Blower Motor
Buck Boost
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 56 —
SECTION 6: PROPANE-BURNER OPERATIONAL OVERVIEW
1. The Interior Switch Panel’s PropaneBurner switch is moved to the ON position authorizing the Propane burner to be
used as a heat source.
10. The Control Thermostat is checked
to ensure there is still a need for heat.
Chart 2
11. The Propane-Burner Controller
continues to run through a cycle of the
following checks until one of these
scenarios does not check out:
2. The Indicator Light on the Interior
Switch Panel’s Propane-Burner switch is
illuminated.



3. The Control Thermostat is checked to
determine if there is a need for additional
heat.


4. The Combustion Blower Fan is
Activated for 15 seconds.
5. The Fan Validation Switch verifies the
Combustion Blower Fan is operating.
Checking for a flame
Checking that the Control Thermostat is still calling for heat
Checking that the interior switch
Panel’s Propane-Burner Switch is
still in the ON position.
Checking that the High-Limit
Thermostats have not over-temped
Checking that the Interlock Switch
has not been tripped
12. The Propane-Burner begins a shutdown procedure when one of the following occurs:


6. The Hot Surface Igniter is activated
for 8 seconds.


7. The Dual Stage Gas Valve is activated, which allows the propane gas to enter
into the Combustion Chamber where it
mixes with air and is ignited by the Hot
Surface Igniter.

The flame extinguishes
The Control Thermostat signals
that there is no longer a need for
heat.
The Propane-Burner switch, on the
Interior Switch Panel, is turned to
the OFF position.
Either of the High-Limit
Thermostats over-temp.
The Interlock Switch is tripped
2 Times
13. The Dual-Stage Gas Valve is
deactivated.
8. The Flame Sensor verifies that a flame
is present.
NO
Inter-Purge
10 seconds
14. A 2-Mintue Purge Cycle takes
place.
YES
9. Hot surface igniter is de-activated.
15. The Combustion Blower Motor is
deactivated
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 57 —
SECTION 6: DIESEL BURNER CONTROLLER WIRING SCHEMATIC
Figure 34
1 - Indicator Light (-)
2 - Indicator Light (+)
3 - A-Fuse
4 - Ground
5 - Thermostat Orange
6 - Thermostat White
7 - Interlock Switch
8 - Left High Limit Thermostat
9 - Left High Limit Thermostat
12 - Right High Limit Thermostat
13 - Right High Limit Thermostat
14 - Stir Pump
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 58 —
SECTION 7: DETACHING
AND
REATTACHING
THE
PROPANE-BURNER
Instructions for Detaching the Propane-Burner
WARNING!
Be sure to move the Burner switch on the Interior Switch Panel to the OFF position and disconnect the Propane
-Burner’s power supply before detaching the Propane-Burner from the Aqua-Hot. Failure to turn off the
Propane-Burner and disconnect power could result in serious bodily injury.
CAUTION!
Be sure to turn off the Propane Fuel Supply at the port on top of the Aqua-Hot prior to beginning this
replacement procedure.
Step 1: Turn Off the Propane-Burner Switch
Figure 37
1. Move the Interior Switch Panel’s Propane-Burner switch to the “OFF” position.
Step 2: Remove the Access Cover
Figure 38
1. Remove the Aqua-Hot’s access cover by locating
the bolts securing it in place.
2. Unscrew the bolt securing the front of the cover in
place.
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 59 —
SECTION 7: DETACHING
3. Unscrew the bolt securing the top of the cover in
place.
Figure 39
AND
REATTACHING
THE
PROPANE-BURNER
4. Lift the access cover off and set it aside.
Figure 39A
Step 3: Disconnect the Propane-Burner from the Propane-Burner Controller
Set Screws
1. Locate both the Propane-Burner’s white, electrical
plug connection to the Propane-Burner Controller
and both of the green plug connections to the
Buck Boosts.
2. Loosen the set screws, securing the green plugs
to the buck boosts,
Figure 40
Figure 40A
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 60 —
SECTION 7: DETACHING
AND
REATTACHING
THE
PROPANE-BURNER
Figure 41
3. Pull the plugs completely out of the Propane-Burner Controller
and the Buck Boosts.
NOTE: There are also 3 wires connected to the propane-burner controller, that will need to be
removed, by firmly pulling on the quick connect terminals.
Step 4: Remove the fuel line from the Propane-Burner
CAUTION!
Be sure to turn off the Propane Fuel Supply at the port on top of the Aqua-Hot prior to beginning this
procedure.
1. Locate the gas valve assembly on the PropaneBurner and the corresponding fuel lines.
Figure 42
2. Using an 11/16 wrench, loosen the nut securing the
fuel line to the gas valve assembly.
Figure 42A
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 61 —
SECTION 7: DETACHING
AND
REATTACHING
THE
PROPANE-BURNER
Step 5: Remove the Propane-Burner from the Aqua-Hot
1. The Propane-Burner is secured to the Aqua-Hot
with four nuts that can be removed by using a 9/16
inch socket wrench with a wobble extension.
2. Carefully lift the Propane-Burner away from the
Aqua-Hot.
Figure 43
Figure 44
3. Remove the Mounting Gasket from the boiler tank’s front plate
and the Propane-Burner.
Figure 45
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 62 —
SECTION 7: DETACHING
AND
REATTACHING
THE
PROPANE-BURNER
Instructions for Reattaching the Propane-Burner
Step 1: Replace the Mounting Gasket
1. Clean the boiler tank’s front plate.
Figure 46
2. Install a new mounting gasket into place.
Figure 47
Step 2: Reinstall the Propane-Burner
1. Align the Propane-Burner’s front air-tube plate
with the combustion chamber and slide onto the
bolts protruding from the boiler tank.
Figure 48
2. Finger tighten all four nuts previously removed to
secure the Propane-Burner to the boiler tank.
Figure 49
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 63 —
SECTION 7: DETACHING
AND
REATTACHING
THE
PROPANE-BURNER
3. Using a 9/16 socket wrench with a wobble extension, tighten
the three nuts securely.
Figure 50
Step 3: Reconnect the Fuel Line
1. Connect the Supply Fuel Line to the PropaneBurner’s Gas Valve Assembly.
2. Using an 11/16 wrench, tighten the nut on the
fuel line to the Gas Valve Assembly to secure
the line in place.
Figure 51
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 64 —
SECTION 7: DETACHING
AND
REATTACHING
THE
PROPANE-BURNER
Step 4: Reconnect the Propane-Burner to the Propane-Burner Controller
1. Connect the propane burner harness to the propane burner controller and buck boost converters. Remember to attach the 3 separate wires,
previously disconnected from the propane burner
controller.
A. Wire #r 86 connects to the PWR terminal.
B. Wire # 92 connects to the BLO terminal.
C. Wire # 82 connects to the HIS+ Terminal
2. Press firmly on connectors to secure them to the
Propane Burner Controller. Secure the Buck Boost
Converter plugs by screwing in the set screws,
previously loosened.
Figure 54
Figure 53
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 65 —
SECTION 7: DETACHING
AND
REATTACHING
THE
PROPANE-BURNER
Step 5: Reinstall the Access Cover
1. Set the access cover back into place on the Aqua-Hot.
Figure 55
2. Insert the bolts in the two locations on the Aqua-Hot to secure the cover in place; tighten the bolts securely.
NOTE: The access cover must be installed prior to operation as
a safety switch exists, which will prevent the Aqua-Hot
from operating whenever the access cover is not properly installed.
CAUTION!
Be sure to turn the Gas Valve, on top of the heater, ON, prior to starting the Propane-Burner. Failure to do so could
result in a Propane-Burner malfunction.
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 66 —
SECTION 8: PROPANE BURNER COMPONENTS
AND
REPAIR INFORMATION
Mounting Gasket:
The Aqua-Hot operates on both AC and DC power. Be
sure to disconnect the 120 Volt-AC power supply from the
Aqua-Hot prior to servicing. Failure to do so could result
in serious personal injury, electrical shock, or even death!
Function:
The Mounting Gasket creates a tight seal between the Combustion Chamber and the Propane-Burner Mounting Plate.
Figure 57
Hot Surface Igniter
Replacement Indicator:
The Mounting Gasket should be replaced each time the
Propane-Burner is detached from the Aqua-Hot.
Replacement Procedure:
The Aqua-Hot operates o both AC and DC power. Be sure
to disconnect the 120 Volt-AC power supply from the Aqua
-Hot prior to servicing. Failure to do so could result in serious personal injury, electrical shock, or even death!
Function:
Be sure to shut off the Fuel Supply line prior to beginning this
replacement procedure.
1.
Follow the “Detaching and Reattaching the PropaneBurner” procedure located in Section 7 of this manual.
2.
Remove the existing Mounting Gasket from the Boiler
Tank’s front plate and from the Propane-Burner Mounting
Plate. Be sure to clean the old gasket completely off of
both plates
3.
4.
Set the replacement Mounting Gasket into place on the
Boiler Tank’s front plate.
Following the procedure for “Detaching and Reattaching
the Propane-Burner,” reattach the Propane-Burner to the
Aqua-Hot.
Be sure to open the shut-off valve for the Fuel Supply prior to
starting the Propane-Burner.
The Hot Surface Igniter ignites the propane fuel. It will activate 15 seconds after the initial start up process begins, and
will be activated 5 seconds prior to the propane dual stage gas
valve opening, to ensure it is up to the proper ignition temperature of 1300° F, before propane enters the burn chamber.
Replacement Indicator:
Replace the Hot Surface Igniter if:
1. It fails to ignite the propane fuel.
2. If it is cracked or damaged.
Troubleshooting
NOTE: The interlock switch will prevent the Propane-Burner
from operating without the access cover intact; therefore, the
switch will need to be manually pressed during this troubleshooting procedure.
1. Turn the Propane-Burner switch to the ON position, on the
interior Switch Panel.
2. After approximately 15 seconds, the Propane-Burner
Controller will activate the Hot Surface Igniter.
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 67 —
SECTION 8: PROPANE BURNER COMPONENTS
AND
REPAIR INFORMATION
Hot Surface Igniter - (continued)
A. Check the Burner Controller for 12 VDC at the
Hot Surface igniter wire, # 82. If no voltage exists
follow the procedure for replacing the Propane
Burner Controller
B. Check the Hot Surface Igniter Buck Boost for 12
VDC at wires #80 and #81. If no voltage is present
follow the procedure for replacing the Buck Boost
converter.
4. With the Hot Surface Igniter removed, and the Propane Gas
Ball Valve closed, turn the Propane-Burner Switch, on the interior switch panel to the ON position.
5. After the 15 second prime cycle, the Propane Burner Controller will activate the Hot surface Igniter.
NOTE: The Hot Surface Igniter will be activated for 10 seconds before the Propane-Burner Controller deactivates it, due
to a no flame condition.
6. After the Hot Surface Igniter is activated, watch the tip to
If voltage does exist:
make sure it gets glowing, red hot.
C. Using a D.C. Clamp-on type amp meter. Test
the Hot surface Igniter wires, #80 or #81, and see
if the Hot Surface Igniter is pulling amps. It
should pull approximately 2 amps. If the Hot surface
Igniter is not pulling any amps follow the Hot
Surface Igniter Replacement Procedure.
7. If the igniter does get glowing, red hot it is working properly. If it does not glow, follow the Hot Surface igniter replacement Procedure.
Replacement Procedure
Visual Inspection Procedure
It is possible to view the Hot Surface Igniter, to verify functionality.
1. Turn the Propane-Burner switch to the OFF position, on the
interior switch panel.
2. Close the Propane Gas Ball Valve, on the top of the heater,
where the propane line connects to the heater.
3. Using a 7/64 Allen Wrench, loosen the Hot Surface
Igniter and remove.
The Hot Surface Igniter is extremely HOT, use caution when
handling or serious burns may occur.
Be careful not to drop or hit the Hot Surface Igniter or serious
damage can occur to the Hot Surface Igniter’s ceramic casing.
The Aqua-Hot operates o both AC and DC power. Be sure
to disconnect the 120 Volt-AC power supply from the Aqua
-Hot prior to servicing. Failure to do so could result in
serious personal injury, electrical shock, or even death!
1. Turn the Propane-Burner Switch to the OFF position, on the
switch panel inside the motor home.
2. Disconnect the wires by pulling firmly on the red quick disconnect fitting.
3. Using a 7/64 Allen Wrench, loosen the Hot Surface Igniter
and remove.
Be careful not to drop or hit the Hot Surface Igniter or serious
damage can occur to the Hot Surface Igniter ceramic casing.
4. Install the replacement Hot Surface Igniter.
5. Using a 7/64 Allen Wrench, tighten the Hot Surface Igniter
in place.
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 68 —
SECTION 8: PROPANE BURNER COMPONENTS
AND
REPAIR INFORMATION
Hot Surface Igniter - (continued)
6. Reconnect the wires previously disconnected.
7. Test for proper operation.
Hot Surface Igniter
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 69 —
SECTION 8: PROPANE BURNER COMPONENTS
AND
REPAIR INFORMATION
Replacement Procedure
Refractory
The Aqua-Hot operates o both AC and DC power. Be sure
to disconnect the 120 Volt-AC power supply from the Aqua-Hot prior to servicing. Failure to do so could result in
serious personal injury, electrical shock, or even death!
1. Turn the Propane-Burner Switch to the OFF position, on the
switch panel inside the motor home.
2. Turn the propane fuel supply valve, located on the top of
the heater, to the OFF position.
3. Loosen and disconnect the propane fuel line, from the dual
stage gas valve, on the propane burner.
Function:
The Refractory acts as an insulator, to protect the hot surface
igniter from being overheated by the flame. Troubleshoot the
Refractory if the propane burner “POPS” on ignition, or if the
propane burner fails to ignite.
Replacement Indicator:
4. Using a 9/16” socket, loosen and remove the four nuts,
securing the propane burner to the heater.
5. Locate and remove the screws securing the defective
refractory to the propane burner.
6. Locate and remove both the Hot Surface Igniter and the
Flame Sensor.
Replace the Refractory if it becomes damaged
7. Remove the defective refractory.
NOTE: Improper handling of the burner may cause the Refractory to shift it’s position on the propane burner, causing it
to cover the hot surface igniter. This will result in the propane
fuel being ignited late, or not at all.
8. Install the replacement refractory onto the propane burner,
ensuring both the flame sensor and hot surface igniter holes
are aligned properly.
9. Reinstall both the Hot Surface Igniter and the Flame Sensor.
Troubleshooting
NOTE: The interlock switch will prevent the Propane-Burner
from operating without the access cover intact; therefore, the
switch will need to be manually pressed during this troubleshooting procedure.
1. Follow the instructions for troubleshooting the Hot Surface
Igniter.
2. If the Hot Surface Igniter is functioning properly follow the
instructions for removing the Propane Burner.
10. Secure the Refractory to the burner using the screw
previously removed.
11. Reinstall the propane burner to the heater, and tighten the
nuts securing the burner in place.
12. Connect the propane fuel line to the dual stage gas valve,
and securely tighten.
13. Turn the propane fuel supply valve to the on position.
14. Test for proper operation.
3. With the Propane Burner removed ensure the Refractory is
securely in place on the propane burner, seated against the
Propane Burner mounting plate.
NOTE: If the Refractory is cracked or damaged, it will need
to be replaced.
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 70 —
SECTION 8: PROPANE BURNER COMPONENTS
AND
REPAIR INFORMATION
Refractory: (Continued)
Flame Sensor
Hot Surface
Igniter
Refractory
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 71 —
SECTION 8: PROPANE BURNER COMPONENTS
Dual Stage Propane Gas Valve
Function:
The Dual Stage Propane Gas Valve will activate approximately 6 seconds after the Hot Surface Igniter has been
activated, to allow propane gas to enter the combustion
chamber.
NOTE: Both Stages of the Dual Stage Propane Gas Valve
must be activated before propane gas will flow into the combustion chamber.
AND
REPAIR INFORMATION
3. Once it has been determined that the Propane-Burner
Controller is sending power to the Dual Stage Propane Gas
Valve, Verify 12 VDC at both sides of the Dual Stage
Propane Gas Valve.
A. Using a Digital Volt Meter, check the #87 (green) wire,
on the right side of the gas valve for 12 VDC, and the #88
(blue) wire, on the left side of the gas valve for 12 VDC.
If no voltage is present inspect wire harness for damage.
NOTE: The #87 (green) and the #88 (blue) wires are spliced
together inside the Propane-Burner Harness, next to White
Propane-Burner controller plug.
Replacement Indicator:
Replace the Dual Stage Propane Gas Valve if either stage fails
to open, Failing to allow propane gas to enter the combustion
chamber.
4. If both stages of the Dual Stage Propane Gas Valve are receiving 12 VDC, but either stage fails to open, the Dual Stage
Propane Gas Valve must be replaced. Follow the Dual Stage
Propane Gas Valve Replacement procedure in this section.
NOTE: Before Troubleshooting the Dual Stage Propane Gas
Valve, verify the coach has propane, and that all Propane shut
off valves are in the open position.
Troubleshooting:
NOTE: The interlock switch will prevent the Propane-Burner
from operating without the access cover intact; therefore, the
switch will need to be manually pressed during this troubleshooting procedure.
1. Turn the Propane-Burner Switch, on the interior switch panel, to the ON position.
NOTE: After the 15 second Prime Cycle, and the 5 second
Hot Surface Igniter Cycle the Propane-Burner should activate
both stages of the Dual Stage Propane Gas Valve.
Dual Stage Propane Gas Valve
2. Once it has been determined that the Dual Stage Propane
Gas Valve should be activated, verify that the Propane
Burner Controller is sending 12 VDC to Both Stages of the
Dual Stage Propane Gas Valve.
Burner
Controller
A. Using a Digital Volt Meter, check the #87 (green) wire,
on the White Plug, plugged into the Propane-Burner
Controller for 12 VDC. If no voltage is present replace
the Propane-Burner Controller.
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 72 —
SECTION 8: PROPANE BURNER COMPONENTS
AND
REPAIR INFORMATION
CAUTION!
Be sure to turn OFF the Propane Fuel Supply, at the port on top of the Aqua-Hot prior to beginning this
replacement procedure.
Dual Stage Propane Gas Valve (continued)
Propane inlet port
ball valve
The Aqua-Hot operates o both AC and DC power. Be sure
to disconnect the 120 Volt-AC power supply from the Aqua
-Hot prior to servicing. Failure to do so could result in
serious personal injury, electrical shock, or even death!
Replacement Procedure:
1. Shut off the propane fuel supply, by turning the propane
inlet port ball valve to the OFF position.
2. Using an 11/16 wrench, remove the propane supply line
from the Dual Stage Propane Gas Valve.
3. Using a 1/2” Wrench, loosen and remove the dual stage
propane gas valve from the propane burner.
NOTE: It may be necessary to use a back up wrench to prevent damage to the propane burner, when removing the dual
stage gas valve.
4. Remove and clean the steel fittings on the defective dual
stage gas valve, to use on the replacement dual stage gas
valve.
5.
Wrap the threads of the steel fittings with a thread sealant
recommended for use with propane gas fittings.
6.
Install the steel fittings onto the dual stage gas valve, as
they were previously removed.
7.
Connect the dual stage gas valve to the propane burner.
8.
Connect the propane supply line to the dual stage gas
valve.
9.
Turn the Propane inlet port ball valve to the ON position.
10. Test for propane leaks.
11. Test for proper operation.
Dual Stage Propane Gas Valve
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 73 —
SECTION 8: PROPANE BURNER COMPONENTS
Combustion Blower Fan
Function:
A. Using a digital volt meter check the #92 wire going into
the Buck Boost Converter for 12 VDC. If there is no
voltage inspect wire for loose connections or damage.
B. If there is power going into the Buck Boost Converter
on wire #92, check wire # 99 for 12 VDC exiting the
Buck Boost Converter, going to the combustion blower
fan.
Replacement Indicator:
Replace the Combustion blower fan if it is damaged or not
working.
NOTE: If the Fan Validation Switch has continuity before the
combustion blower fan is activated the Propane Controller will
not allow the combustion blower fan to start.
NOTE: If the air shutter is not adjusted properly the burner
may not ignite, or it may make a loud rumbling sound. For
proper adjustment procedure reference Appendix E.
Troubleshooting:
REPAIR INFORMATION
5. If the Right D.C. Hi-Limit thermostat is functioning
properly, verify that the Buck Boost Converter for the
Blower motor is operating properly.
The Combustion Blower fan creates combustion air, which
is blown into the combustion chamber to mix with the propane fuel, before it is ignited. Reference Appendix E for
the proper adjustment procedure.
NOTE: The interlock switch will prevent the Propane-Burner
from operating without the access cover intact; therefore, the
switch will need to be manually pressed during this troubleshooting procedure.
AND
If there is power going to the Combustion Blower Fan, but it
still fails to operate, replace the Combustion Blower Fan.
Replacement Procedure:
1. Turn the Propane-Burner Switch to the OFF position on the
Interior Switch Panel, inside the motor home.
2. Disconnect the wires, connecting the combustion blower
fan to the harness.
3. Using a 3/8” socket, loosen the nuts securing the combustion blower fan to the propane burner. Reference figure ?.
4. Discard the gasket sealing the combustion blower fan to the
propane burner.
1. Turn the Propane-Burner Switch to the ON position, on the
Interior Switch Panel.
2. Verify the following:
A. The control Thermostat is calling for heat.
B. The interlock switch is not tripped.
C. The float switch is not tripped.
D. There is 12 VDC going to the Propane-Burner
Controller.
3. Verify that the Propane-Burner Controller is sending power
to the combustion blower motor.
A. Using a digital Voltmeter check wire #92 (green) for 12
VDC, at the white plug, plugged into the Propane
Burner Controller. If no voltage is present replace the
Propane-Burner Controller.
5.
Using a Phillips head screwdriver, and a 9mm socket, remove the air shutter assembly from the defective combustion blower fan. Reference Figure ?.
6.
Using a Phillips head screwdriver and a 9mm socket, install the Air shutter assembly onto the replacement combustion blower fan. Torque = 12 in/lbs.
7.
Replace discard gasket with a new replacement gasket.
8.
Using a 3/8” socket. Secure the combustion blower fan
assembly to the propane burner. Torque = 35 in/lbs.
9.
Reconnect the wires, previously disconnected.
10. Test for proper operation.
4. If the Propane-Burner Controller is sending power out on
wire #92 (green), verify that the right hi-limit thermostat is
operating properly. Follow the troubleshooting guide for
the Right D.C. Hi-Limit thermostat in section 4.
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 74 —
SECTION 8: PROPANE BURNER COMPONENTS
AND
REPAIR INFORMATION
Gasket
Combustion Blower Fan
Propane Burner
Controller
3/8” Socket
Phillips
Screwdriver
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
9mm Socket
— Page 75 —
SECTION 8: PROPANE BURNER COMPONENTS
Exhaust “High Back Pressure” Switch
REPAIR INFORMATION
Replacement Procedure:
1.
Disconnect the two wires, connected to the switch, by
firmly pulling on the quick disconnect terminals.
2.
Using a 5/32” Allen Wrench, loosen the two screws, securing the switch to the left side of the propane burner.
3.
Remove the defective switch.
4.
Secure the replacement switch to the side of the propane
burner, using the screws previously removed.
5.
Reconnect the wires, previously removed from the defective switch.
6.
Test for proper operation.
Function:
The purpose of the Exhaust “High Back Pressure” Switch, is to
monitor back pressure inside the combustion chamber, and shut
the burner down if it senses high back pressure. It is normally
closed, and if it senses high back pressure it will trip and will
interrupt the Flame Sensor signal, shutting down the propane
burner.
AND
Replacement Indicator:
Replace the Exhaust “High Back Pressure” Switch if it fails to
operate properly or is damaged.
Troubleshooting Procedure:
NOTE: The interlock switch will prevent the Propane-Burner
from operating without the access cover intact; therefore, the
switch will need to be manually pressed during this troubleshooting procedure.
1. Turn the Propane-Burner Switch, on the interior switch
panel to the OFF position, and let the Propane-Burner
completely shut down.
Exhaust “High Back
Pressure” switch
2. Located the Exhaust “High Back Pressure” Switch, on the
left side of Propane Burner.
3. Disconnect the two wires, connected to the switch, by
firmly pulling on the quick disconnect terminals.
4. Using a Digital Voltmeter, check the Exhaust “High Back
Pressure” Switch for continuity.
A. If no continuity exists replace the Exhaust “High Back
Pressure” Switch.
B. If there is continuity while the propane burner is off,
inspect exhaust for signs of damage, that may cause
back pressure into the exhaust chamber.
NOTE: Before Replacing the High Back Pressure Switch, it
is recommended to inspect the exhaust pipe for damage or
restrictions.
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 76 —
SECTION 8: PROPANE BURNER COMPONENTS
Fan Validation Switch
AND
REPAIR INFORMATION
C. With the combustion blower fan running, using a digital
voltmeter and re-check the fan validation switch for
continuity .
Function:
The purpose of the Fan Validation Switch, is to monitor the
combustion blower fan, and verify that it is operating properly.
The Fan Validation Switch is normally open.
i. If there is continuity, with the combustion blower fan
running the fan validation switch is operating
properly.
ii. If there is no continuity, with the combustion blower
fan running, the fan validation switch is defective
and will need to be replaced.
Replacement Indicator:
Replace the Fan Validation Switch if it fails to operate properly or is damaged.
Replacement Procedure:
Troubleshooting Procedure:
1.
Disconnect the two wires, connected to the fan validation
switch, by firmly pulling on the quick disconnect
terminals.
2.
Using a 5/32” Allen Wrench, loosen the two screws, securing the fan validation switch to the Right side of the propane burner.
3.
Remove the defective fan validation switch.
4.
Secure the replacement fan validation switch to the side of
the propane burner, using the screws previously removed.
5.
Reconnect the wires, previously removed from the defective fan validation switch.
6.
Test for proper operation.
NOTE: The interlock switch will prevent the Propane-Burner
from operating without the access cover intact; therefore, the
switch will need to be manually pressed during this troubleshooting procedure.
NOTE: If the Fan Validation Switch has continuity before the
combustion blower fan is activated the Propane Controller will
not allow the combustion blower fan to start
1. Turn the Propane-Burner Switch, on the interior switch panel to the OFF position, and let the Propane-Burner completely shut down.
2. Locate the Fan Validation Switch, on the right side of Propane Burner.
Fan Validation
Switch
3. Disconnect the two wires, connected to the switch, by firmly pulling on the quick disconnect terminals.
4. Using a Digital Voltmeter, check the fan validation switch
for continuity.
A. If continuity exists when the combustion blower fan is
NOT running replace the fan validation switch.
B. If there is no continuity while the propane burner is off,
Turn the Propane Burner to the ON position, and verify
that the combustion blower fan is running.
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 77 —
SECTION 8: PROPANE BURNER COMPONENTS
AND
REPAIR INFORMATION
that the combustion blower fan is running.
Fan Validation Switch Relay
C. With the combustion blower fan running, using a digital
voltmeter and re-check the fan validation switch relay
for continuity .
Function:
The purpose of the Fan Validation Switch Relay , is to reduce
the amount of amps going to the Fan Validation Switch. It
takes the normal .5 amps and reduces it to .1 amps, to extend
the life of the Fan Validation Switch.
i. If there is continuity, with the combustion blower fan
running the fan validation switch is operating
properly.
ii. If there is no continuity, with the combustion blower
fan running, the fan validation switch is defective
and will need to be replaced.
Replacement Indicator:
Replace the Fan Validation Switch Relay if it fails to operate
properly or is damaged.
NOTE: The interlock switch will prevent the Propane-Burner
from operating without the access cover intact; therefore, the
switch will need to be manually pressed during this troubleshooting procedure.
Troubleshooting Procedure:
1. Turn the Propane-Burner Switch, on the interior switch panel to the OFF position, and let the Propane-Burner completely shut down.
Replacement Procedure:
1.
Locate the Fan Validation Switch Relay.
2.
Disconnect the wires connected to the Fan Validation
Switch Relay. Note the location of each wire.
3.
Reconnect the wires to the new Fan Validation Switch
Relay, refer to the wiring diagram in appendix A for proper placement of the wires on the relay.
4.
Test for proper operation
2. Locate the Fan Validation Switch Relay, on the right side
of Propane Burner.
3. Disconnect the two wires, #84 & #91, connected to the relay, by firmly pulling on the quick disconnect terminals.
4. Using a Digital Voltmeter, check the fan validation switch
Relay for continuity.
Fan Validation
Switch Relay
A. If continuity exists when the combustion blower fan is
NOT running replace the fan validation switch Relay.
B. If there is no continuity while the propane burner is off,
Turn the Propane Burner to the ON position, and verify
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 78 —
Buck Boost Converter - Combustion Blower Fan
Function:
The purpose of the Buck Boost Converter is to maintain a preset
output voltage,
NOTE: There are two different Buck Boost Converters. One is
for the Combustion Blower Fan, and the other one is for the Hot
Surface Igniter.
Replacement Indicator:
Replace the Buck Boost Converter if it fails to
operate properly or is damaged.
Troubleshooting Procedure:
NOTE: The interlock switch will prevent the Propane-Burner
from operating without the access cover intact; therefore, the
switch will need to be manually pressed during this troubleshooting procedure.
1. Turn the Propane-Burner Switch to the ON position, on the
Interior Switch Panel.
5. If the propane Burner Controller is sending power and
ground to the buck boost converter, verify that the buck
boost converter is receiving the power and ground signals.
Through the individual wires. The power wire is #92, the
ground wire is #95.
A. If an individual wire is not sending the proper
signal, replace that individual wire.
6. Verify that the buck boost converter is sending power and
ground to the combustion blower motor, wire #99 is the
power wire, and wire #98 is the ground. This voltage should
be approximate 12.5 VDC, when the supply voltage is between 11 VDC - 15 VDC.
A. If the voltage going to the motor, from the buck boost
converter is not 12.5 VDC, when the supply voltage is
between 11 VDC - 15 VDC replace the buck boost
converter.
Combustion Blower Fan
Buck Boost Converter
2. Verify the following:
A. The control Thermostat is calling for heat.
B. The interlock switch is not tripped.
C. The float switch is not tripped.
D. There is 12 VDC going to the Propane-Burner
Controller.
3. Verify that the Propane-Burner Controller is sending power
to the Buck Boost Converter at the BLO pin, on the controller.
A. If the propane burner controller is not sending a power
signal to the buck boost converter, replace the propane
burner controller.
4. Verify that the Propane Burner Controller is sending a ground
signal to the buck boost converter at the GND pin, on the
Controller
B. If the propane burner controller is not sending a ground
signal to the buck boost converter, replace the propane
burner controller.
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 79 —
Buck Boost Converter - Hot Surface Igniter
Function:
The purpose of the Buck Boost Converter is to maintain a preset
output voltage,
NOTE: There are two different Buck Boost Converters. One is
for the Combustion Blower Fan, and the other one is for the Hot
Surface Igniter.
Replacement Indicator:
Replace the Buck Boost Converter if it fails to
operate properly or is damaged.
Troubleshooting Procedure:
NOTE: The interlock switch will prevent the Propane-Burner
from operating without the access cover intact; therefore, the
switch will need to be manually pressed during this troubleshooting procedure.
B. If the propane burner controller is not sending a ground
signal to the buck boost converter, replace the propane
burner controller.
5. If the propane Burner Controller is sending power and
ground to the buck boost converter, verify that the buck
boost converter is receiving the power and ground signals.
Through the individual wires. The power wire is #82, the
ground wire is #11.
A. If an individual wire is not sending the proper
signal, replace that individual wire.
6. Verify that the buck boost converter is sending the proper
power and ground signals to the hot surface igniter, wire #80
is the power wire, and wire #81 is the ground wire. This
voltage should be approximate 12.5 VDC, when the supply
voltage is between 11 VDC - 15 VDC.
A. If the voltage going to the motor, from the buck boost
converter is not 12.5 VDC, when the supply voltage is
between 11 VDC - 15 VDC replace the buck boost
converter.
1. Turn the Propane-Burner Switch to the ON position, on the
Interior Switch Panel.
2. Verify the following:
A. The control Thermostat is calling for heat.
B. The interlock switch is not tripped.
C. The float switch is not tripped.
D. There is 12 VDC going to the Propane-Burner
Controller.
Hot Surface Igniter
Buck Boost Converter
3. Verify that the Propane-Burner Controller is sending power
to the Buck Boost Converter at the HSI pin, on the controller.
A. If the propane burner controller is not sending a power
signal to the buck boost converter, replace the propane
burner controller.
4. Verify that the Propane Burner Controller is sending a ground
signal to the buck boost converter at the GND pin, on the
Controller
NOTE: The Propane Burner Controller sends a GND signal out
on wire #95. Wire #95 then goes to the combustion blower fan’s
buck boost, and is tied into Wire #11, which is the ground wire
for the Hot Surface Igniter’s buck Boost.
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 80 —
SECTION 8: PROPANE BURNER COMPONENTS
AND
REPAIR INFORMATION
Flame Sensor
Function:
The purpose of the Flame Sensor, is to monitor the flame of the
propane burner and verify that it is burning properly. The
flame sensor turns the heat from the flame into a mili-volt signal that the propane burner controller senses.
Replacement Indicator:
Replace the Flame Sensor if it fails to operate properly or is
damaged.
Troubleshooting Procedure:
NOTE: The interlock switch will prevent the Propane-Burner
from operating without the access cover intact; therefore, the
switch will need to be manually pressed during this troubleshooting procedure.
1.
Flame current is the current which passes through the
flame from the sensor to ground to complete the primary
safety circuit. The minimum flame current necessary to
keep the system from lockout is 0.7µA microamps. To
measure flame current, DISCONNECT INPUT VOLTAGE, then insert a 0-50µA DC meter and capacitor in series with the sensor electrode and wire per Figure 5. Meter
should read 0.7µA or higher while flame is established. If
meter reads below “0” on scale, meter leads are reversed.
Disconnect power and reconnect meter leads for proper
polarity.
Flame Sensor
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 81 —
SECTION 8: PROPANE BURNER COMPONENTS
Fenwal Burner Controller
Function:
When a call for heat is received from the control thermostat
supplying 12 volts to PWR, the controller will reset, perform a
self check routine, and a pre-purge delay begins. Following the
pre-purge period the gas valve is energized and the hot surface
igniter will commence for the trial for ignition period.
When flame is detected during the trial for ignition, the hot
surface igniter is shut off immediately and the gas valve remains energized. The thermostat and main burner flame are
constantly monitored to assure the system continues to operate
properly. When the thermostat is satisfied and the demand for
heat ends, the main valve is de-energized immediately.
Replacement Indicator:
Replace the Propane Burner Controller if it fails to operate
properly or is damaged.
Troubleshooting Procedure:
NOTE: The interlock switch will prevent the Propane-Burner
from operating without the access cover intact; therefore, the
switch will need to be manually pressed during this troubleshooting procedure.
Failure to Light - Lockout
AND
REPAIR INFORMATION
Flame Failure - Re-Ignition
1.
If the established flame signal is lost while the burner is
operating, the control will respond within 0.8 seconds.
The Hot Surface Igniter will be energized for a trial for
ignition period in an attempt to relight the burner. If the
burner does not light, the controller will de-energize the
gas valve. The controller will make two more attempts to
relight the burner. If the burner does no relight, the control
will go into lockout as noted above in “Failure to Light”.
If the flame is re-established, normal operation resumes.
Flame Current Check
1.
Flame current is the current which passes through the
flame from the sensor to ground to complete the primary
safety circuit. The minimum flame current necessary to
keep the system from lockout is 0.7µA microamps. To
measure flame current, DISCONNECT INPUT VOLTAGE, then insert a 0-50µA DC meter and capacitor in series with the sensor electrode and wire per Figure 5. Meter
should read 0.7µA or higher while flame is established. If
meter reads below “0” on scale, meter leads are reversed.
Disconnect power and reconnect meter leads for proper
polarity.
When monitoring flame current, use a 1.5µF \by pass capacitor
to protect the meter from damage.
1. Should the Propane Burner fail to light, or the flame is not
detected during the first trial for ignition period, the gas
valve is de-energized and the control goes through an interpurge delay before another ignition attempt. The controller
will attempt two additional trials before going into lockout
and the valve relay will be de-energized immediately.
NOTE: Recover from lockout requires a manual reset by
removing 12 VDC for a period of 5 seconds.
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 82 —
SECTION 8: PROPANE BURNER COMPONENTS
AND
REPAIR INFORMATION
Fenwal Burner Controller
Fenwal Burner
Controller
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 83 —
SECTION 8: PROPANE BURNER COMPONENTS
AND
REPAIR INFORMATION
Fenwal Burner Controller
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 84 —
SECTION 10: TROUBLE SHOOTING
This troubleshooting section has been separated into various
Aqua-Hot troubleshooting scenarios, which may be experienced by the heater. This troubleshooting section will begin
with the most probable cause of failure and the corresponding
remedy and will advance to the least probable cause and remedy in order to expedite the troubleshooting process and pinpoint the problem quickly. If additional assistance is needed,
please contact the Aqua-Hot Heating Systems Technical Support Department by phone at 1-800-685-4298 (Monday through
Friday, 7:00 AM to 4:00 PM Mountain Standard Time) or
through Aqua-Hot Heating Systems’ website by going to
www.aquahot.com and clicking on the “Contact Us” link, then
filling out the contact information for submittal.
The Aqua-Hot operates on both AC and DC power. Be
sure to disconnect the 120 Volt-AC power supply from the
Aqua-Hot prior to servicing. Failure to do so could result
in serious personal injury, electrical shock, or even death!
NOTE: Be sure to check the Interior Switch Panel’s DieselBurner switch for a blinking fault code prior to completing the following troubleshooting procedures.
NOTE: Please note that, due to the Interlock Safety Switch,
the Aqua-Hot will not operate if the access cover is
removed.
The Propane-Burner switch has been turned on; however, the Propane-burner fails to operate:
1.
Is the Propane-Burner switch’s indicator light illuminated?
A. NO
a.
c.
d.
e.
f.
Check for 12-Volt power at the B-fuse on the fuse block - does it exist?
Test the float switch for functionality.
Check the Propane-Burner switch for functionality.
Check the Interlock switch for functionality.
Check the fan validation switch for continuity. If there is continuity before the combustion blower fan starts to run, the
propane burner controller will not allow the combustion blower fan to run.
B. YES
b.
e.
f.
Check the Control Thermostat (The Aqua-Hot’s normal operating range is 160-190°F) for functionality by locating the
control thermostat on the heater, disconnecting the wires and placing a jumper wire on the harness between
wires #10 & #11.
Check the Propane-Burner Controller for functionality.
Check the Propane-Burner’s Blower Motor for functionality by placing a direct power and ground source to the motor
and checking for operation.
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 85 —
SECTION 10: TROUBLE SHOOTING
The Propane-Burner switch has been turned on, and the Propane-burner’s Blower Motor has begun
to operate; however, the Propane-burner does not ignite:
1.
2.
3.
4.
5.
6.
7.
Test both of the Propane-Burner’s High-Limit Thermostats for continuity; if continuity does not exist, press the reset button on
the High-Limit Thermostat.
Check the vehicle’s fuel supply to ensure that an adequate amount of fuel exists.
Check the Propane Burner’s High back Pressure Switch for proper functionality
Check the Propane-Burner’s Hot Surface Igniter for proper functionality.
Check the Propane-Burner’s Flame Sensor for proper functionality
Check the Propane-Burner’s Dual Stage Gas Valve for Proper functionality
Check the Combustion Blower Fan Air Adjustment setting, and adjust if necessary
The Propane-Burner switch has been turned on; however, multiple attempts are required before
the Propane-burner will ignite:
1.
2.
3.
Check the Propane-Burner’s Hot surface Igniter for proper functionality.
Check The Flame Sensor.
Check the Combustion Blower Fan Air Adjustment setting
The Aqua-Hot’s exhaust system “Woofs/Pops” when the Propane-burner is ignites:
1.
Check The Propane-Burner’s Hot surface Igniter for proper functionality.
The Propane-burner will ignite, but short cycles
(only runs for a short amount of time before shutting down)
1.
2.
3.
4.
5.
Check The Propane-Burner’s control thermostat for proper functionality.
Check the Propane-Burner’s Flame Sensor for proper functionality
Check the Propane-Burner’s High Back Pressure Switch for proper functionality
Verify the exhaust pipe is not damaged or plugged, which would cause high back pressure.
Verify the Exhaust Tip has been properly installed.
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 86 —
SECTION 10: TROUBLE SHOOTING
The Aqua-Hot is operating, but an interior and/or fresh water tank heating zone is not working.
1.
2.
3.
4.
5.
6.
7.
Is the Low Temp Cutoff Thermostat Tripped?
A. Unhook Thermostat Wires and using a volt meter, check thermostat for continuity.
Verify that the heat exchangers in that zone are working.
Check for loose wires.
Ensure that the check valve is not stuck in a closed position.
While the circulation pump is running, place hand on lines to check for the presence of hot antifreeze and water heating solution.
Is the Zone Relay functioning properly?
Is the Room Thermostat signaling the Aqua-Hot heater?
The Aqua-Hot is at operating temperature; however, the interior and/or fresh water tank
heat exchanger fans are not operating:
1.
2.
3.
4.
5.
6.
When each particular zone’s room thermostat is turned on, does the corresponding relay activate?
Is the Low Temp Cutoff Thermostat tripped?
A. Unhook Thermostat Wires and using a volt meter, check thermostat for continuity.
Check for power at the relay for the fans, Pin (8).
Check the heat exchanger for loose wires.
Using a voltmeter, check for 12-Volts at the malfunctioning fan.
If applicable, is the switch for the fan on?
The Aqua-Hot is operating, but the domestic hot water system is not producing hot water.
1.
2.
3.
4.
5.
6.
7.
8.
9.
Reference Section 1, pages 13-14, and ensure that the Aqua-Hot is using the appropriate antifreeze type and mixture ratio.
Verify that the water outlet’s domestic hot water flow rate is at or below 1.25 Gallons per Minute (GPM).
Verify that the outside water faucet is turned off.
Is the propane-burner operating?
Verify that the tempering valve is properly adjusted. Temperature of water coming out of hot water faucet should be between
115° F - 123° F.
Ensure that the Low-Temp Cut-Off Thermostat is operating properly.
Ensure that the Boiler Tank’s Stir Pump is operating.
Check Temperature of the cold water coming in.
Make sure the heater has not been bypassed.
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 87 —
SECTION 10: TROUBLE SHOOTING
The Electric Element switch has been turned on; however, the Aqua-Hot’s 120 volt-ac electric heating
element does not operate (i.e., lack of hot water and/or interior heat):
NOTE: The Aqua-Hot is not designed to provide continuous hot water
using the Electric Heating Element only.
1.
2.
3.
4.
5.
Ensure that the motor home is plugged into shore power or has the generator running.
Ensure the Aqua-hot is not up to maximum operating temperature, by checking it with a digital thermometer.
With the Interior Switch Panel’s Electric Element switch on, locate the Electric Element’s 120VAC relay and check for DC voltage at Pin #0 (+) and Pin #1 (-); reference Appendix A.
Ensure that the 12 Volt switch is turned on and that the relay engages.
Test the VAC Relay to ensure that it is working properly, using extreme caution.
A. With the Electric Element switch on, check for AC voltage at both VAC power supply terminals on the relay (terminals #4
and #2).
B. Inspect the VAC Relay and the Relay’s wires for damage.
C. Turn the VAC Breaker off and disconnect both VAC power supply wires from the VAC Relay terminals. Turn the Electric
Element switch on and off while checking for continuity across the two open terminals on the VAC Relay. If no continuity
exists, replace the VAC Relay.
6.
Check the Electric Heating Element’s High-Limit Thermostat for continuity; if no continuity, press the reset button on the thermostat.
7.
Verify that the 120 Volt-AC Electrical Heating Element is operating properly.
A. Disconnect the motor home from VAC shore power and switch off the motor home’s generator.
B. Detach and remove the propane-Burner.
C. Check the Electric Heating Element for continuity. If no continuity, replace the Electric Heating Element.
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
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APPENDIX A: WIRING DIAGRAM -
MANUFACTURED BEFORE
JANUARY 2011
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
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APPENDIX A: WIRING DIAGRAM -
MANUFACTURED
BETWEEN JANUARY 2011 THRU AUGUST 2011
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
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APPENDIX A: WIRING DIAGRAM
-
MANUFACTURED AFTER
09/01/2011
NOTE: Heaters starting with serial numbers A375-10060 will require this wiring schematic. Starting with this serial number the
Low Temperature Cut-Off Thermostat will shut down both the interior heating zone fans, and the zone circulation pump, when running hot water.
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
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APPENDIX B: WIRE GAUGE CHART
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
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APPENDIX C: WINTERIZATION PROCCESS
Not winterizing the Aqua-Hot when freezing temperatures
are present will result in serious damage to the Aqua-Hot’s
Domestic Water Heating System. Also, be sure to use an
FDA approved, “GRAS” rated antifreeze for winterization.
NOTE: The Aqua-Hot can continue to be used for interior
zone heating once the domestic water heating system
has been drained and winterized.
The Aqua-Hot’s Domestic Water Heating System must be
completely drained of domestic water any time the heater is
stored where freezing temperatures may be experienced.
Winterizing the Domestic Water Heating System:
Please follow these instructions when winterizing the AquaHot’s Domestic Water Heating System; reference Figure 89:
1.
Completely drain the fresh water storage tank.
2.
Disconnect the domestic water demand pump’s suction
line from the fresh water storage tank.
3.
Attach an adequate piece of hose onto the suction side of
the domestic water demand pump.
4.
Place the opposite end of the hose into an adequate supply
of FDA-approved “GRAS” RV Antifreeze.
5.
Open and close all interior and exterior water faucets, one at
a time, until only pure RV Antifreeze is present. Perform
this procedure for both the hot and cold faucets.
6.
Remove the hose and reconnect the domestic water demand
pump’s suction line to the fresh water storage tank.
An FDA approved “GRAS” rated winterization antifreeze
must be used. YOU CANNOT BLOW DOMESTIC WATER
COIL OUT WITH AIR TO WINTERIZE AQUA-HOT.
De-Winterizing the Domestic Water Heating System:
For de-winterization, completely fill the fresh water storage tank.
Open and close all interior and exterior water faucets, one at a
time, until only clear water is present/visible.
Reference Figure 8.
If disinfecting the potable water system after de-winterizing, be
sure to follow RVIA’s “Instructions for Disinfection of Potable
Water Systems on Recreation Vehicles.” These instructions
can be obtained by contacting the Recreational Vehicle Industry
Association at (703) 620-6003, visiting them online at
www.rvia.com, or writing to them at the following address:
Recreation Vehicle Industry Association
1896 Preston White Drive
P.O. Box 2999
Reston, VA 20195-0999
Arrows indicate directional flow
Aqua-Hot 375LP Heater
Figure 89
To Hot Water Faucets
Domestic
Hot Water
Outlet
Domestic
Cold Water
Inlet
Fresh
Water Storage
AT—Indicates options for mounting an
Accumulator Tank.
To Cold WaDemand
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 93 —
APPENDIX D: EXTREME COLD WEATHER OPERATION
Propane-Burner
When storing the Motor home: Not winterizing the AquaHot when freezing temperatures are present will result in
serious damage to the Aqua-Hot’s Domestic Water Heating
System. Also, be sure to use an FDA approved, “GRAS”
rated antifreeze for winterization.
1. If the Propane-Burner Fails to operate:
A. Is there propane in the motor home?
NOTE: The Aqua-Hot can continue to be used for interior
zone heating once the domestic water heating system
has been drained and winterized.
120 Volt-A.C. Electric Heating Element
Please note that the 120 Volt-AC Electric Heating Element is
the Aqua-Hot’s secondary heat source for heating both the
interior and/or the domestic hot water during low heating demand situations (such as when moderate ambient temperatures
exist and/or when there is a low demand for domestic hot water).
NOTE: In extreme cold weather it may be necessary to activate the 120 Volt-A.C. Electric Heating Element for
1 - 2 hours prior to activating the burner to preheat the
burner, on the initial start up cycle only.
If the 120 Volt-AC Electric Heating Element is not providing
enough heat, turn the Propane-Burner on, in conjunction with
the 120 Volt-AC Electric Heating Element.
Figure 90
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 94 —
APPENDIX D: EXTREME COLD WEATHER OPERATION
If there is a lack of interior Heat:
Note:
The 120 Volt-AC Electric Heating Element is
the Aqua-Hot’s secondary heat source for heating both
the interior and/or the domestic hot water during low heating demand situations (such as when moderate ambient
temperatures exist and/or when there is a low demand for
domestic hot water). If the ambient temperature is ex-
1. Is the Propane-Burner activated?
2. Is the Propane-Burner operating Properly?
3. What is the antifreeze concentration, inside of the
Aqua-Hot Boiler Tank?
4. Was the heating system properly installed, following the
375 LP installation manual?
Figure 91
A. Are there at least 5 heat exchangers installed in
the Interior of the motor home?
B. Are there cold air returns installed for every heat
exchanger? Reference Figure 92.
C. Are the heat exchangers mounted as close to the
hot air outlet grill as possible? Reference
Figure 91.
Figure 92
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 95 —
APPENDIX E: PROPANE BURNER COMBUSTION AIR ADJUSTMENT PROCEDURE
1. Locate and Remove the Access Cover.
Reference figure 1.
NOTE: The interlock switch will prevent the Propane-Burner
from operating without the access cover intact; therefore, the
switch will need to be manually pressed during this adjustment
procedure.
2. Locate the Combustion blower fan, located on the top of the propane burner. Reference figure 2.
3. Using a 7/64 Allen Wrench Loosen the
locking screw, which secures the Air
Shutter Assembly to the Combustion
Blower Fan. Reference figure 3.
NOTE: When adjusting the air on the propane burner inspect
the flame through the sight glass. The fist part of the flame
should be glowing blue and the burner mixing tube should be
glowing orange. Reference figures 4 & 5.
Access
Cover
Figure E1
Interlock
Switch
4. Adjust the air as needed by turning the
air shutter.
Combustion
Blower
fan
5. Using a 7/64 Allen Wrench tighten the
locking screw, which secures the Air
Shutter Assembly to the Combustion
Blower Fan.
6. Install the Access Cover.
Figure E2
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 96 —
APPENDIX E: PROPANE BURNER COMBUSTION AIR ADJUSTMENT PROCEDURE
Locking
Screw
Air
Shutter
Assembly
Figure E3
Sight
Glass
Mixing
Tube
Figure E4
Figure E5
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
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© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 98 —
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 99 —
AHE-375-P02
SERVICE MANUAL
15549 East Highway 52 | Fort Lupton, CO 80621
Toll free: 800.685.4298 | phone: 303.659.8221 | fax:303.857.7881
www.aquahot.com
© 2012 Aqua-Hot® 375P02 - LP Hydronic Heating System Service Manual—Rev. D
— Page 100 —
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