Warning: If the information in this manual 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 vapor and liquids in the
vicinity of this or any other appliance.
Improper installation, adjustment, alteration, service or maintenance can
cause injury or property damage. Refer to this manual. For assistance or
additional information consult a qualified installer, service agency or the
gas supplier. In the Commonwealth of Massachusetts this product must
be installed by a licensed plumber or gas fitter.
Upon completion of the installation, these instructions should be handed
to the user of the appliance for future reference.
What to do if you smell gas
• Close gas valve. Open windows.
• Do not try to light any appliance.
• Do not touch any electrical switch; do not use any phone in your
building.
• Immediately call your gas supplier from a neighbor’s phone. Follow
the gas supplier’s instructions.
• If you cannot reach your gas supplier, call the fire department.
• Installation and service must be performed by a qualified installer,
service agency or the gas supplier.
INDOOR MODEL Flow Modulated with Standing pilot
520 PN
520-PN-N / 520-PN-L
6 720 644 947 (2014/11) US
Suitable for heating potable water only - Not approved for space heating purposes
(Intended for variable flow applications with steady cold water inlet temperatures)
2 | Index
Index
1 Key to symbols and safety instructions . . . . . . . . . . . . 3
1.1 Key to symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2 Safety instructions . . . . . . . . . . . . . . . . . . . . . . . . . 3
2 Warning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3 Appliance details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.1 520 PN specifications (Technical data) . . . . . . . .
3.2 Unpacking the 520PN heater . . . . . . . . . . . . . . . . .
3.3 General rules to follow for safe operation . . . . . . .
3.4 Dimensions and installation clearances . . . . . . . . .
4 Installation instructions . . . . . . . . . . . . . . . . . . . . . . . .
4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.2 Proper location for installing your heater . . . . . .
4.3 Heater placement and clearances . . . . . . . . . . . .
4.4 Mounting Heater . . . . . . . . . . . . . . . . . . . . . . . . . .
4.5 Combustion air requirements . . . . . . . . . . . . . . . .
4.6 Venting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.6.1Horizontal venting . . . . . . . . . . . . . . . . . . . . . . . . .
4.6.2Vertical venting . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.7 Gas piping & connections . . . . . . . . . . . . . . . . . . .
4.8 Measuring gas pressure . . . . . . . . . . . . . . . . . . . .
4.9 Water connections. . . . . . . . . . . . . . . . . . . . . . . .
4.10 Recirculation application . . . . . . . . . . . . . . . . . . .
7
7
8
8
9
10
10
10
11
11
12
13
13
13
15
19
19
20
7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
7.2 Pilot does not light . . . . . . . . . . . . . . . . . . . . . . . . 25
7.3 Pilot lights, but goes out when button is
released . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
7.4 Pilot goes out during or after hot water use . . . . . 26
7.5 Burners do not light with water flow . . . . . . . . . . 26
7.6 Hot water temperature fluctuates at tap . . . . . . . 26
7.7 Water is too hot . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
7.8 Water is not hot enough . . . . . . . . . . . . . . . . . . . . 27
7.9 Burners ignite without hot water flow . . . . . . . . . 27
7.10 Low hot water pressure . . . . . . . . . . . . . . . . . . . . 27
7.11 Noise when heater is running . . . . . . . . . . . . . . . . 28
7.12 Burners do not operate cleanly; yellow flames when
operating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
8 Protecting the environment . . . . . . . . . . . . . . . . . . . . 28
9 Interior components and diagram parts list . . . . . . .
9.1 Interior components . . . . . . . . . . . . . . . . . . . . . . .
9.2 Components diagram . . . . . . . . . . . . . . . . . . . . . .
9.3 Parts list . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
29
29
30
31
10 LIFETIME LIMITED WARRANTY FOR BOSCH TANKLESS
WATER HEATERS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
11 Installer Checklist to be completed by installer upon
installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
5 Operation instructions . . . . . . . . . . . . . . . . . . . . . . . . .
5.1 For your safety read before operating your water
heater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.2 Lighting instructions . . . . . . . . . . . . . . . . . . . . . . .
5.3 To turn off appliance . . . . . . . . . . . . . . . . . . . . . . .
5.4 Setting the water temperature . . . . . . . . . . . . . . .
5.5 Draining water from heater . . . . . . . . . . . . . . . . . .
20
20
21
22
22
23
6 Maintenance and service . . . . . . . . . . . . . . . . . . . . . . .
6.1 Maintenance intervals . . . . . . . . . . . . . . . . . . . . . .
6.2 Water valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.3 Pilot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.4 Main burners . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.5 Vent assembly / heat exchanger . . . . . . . . . . . . . .
6.6 Mineral scale build-up . . . . . . . . . . . . . . . . . . . . . .
6.6.1Descaling heat exchanger . . . . . . . . . . . . . . . . . . .
23
23
23
24
24
24
24
24
7 Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
6 720 644 947 (2014/11)
520 PN
Key to symbols and safety instructions | 3
1
Key to symbols and safety instructions
1.1
Key to symbols
Warnings
Warnings in this document are identified by
a warning triangle printed against a grey
background.
Keywords at the start of a warning indicate
the type and seriousness of the ensuing risk
if measures to prevent the risk are not taken.
The following keywords are defined and can be used in this
document:
• DANGER indicates a hazardous situation which, if not
avoided, will result in death or serious injury.
• WARNING indicates a hazardous situation which, if not
avoided, could result in death or serious injury.
• CAUTION indicates a hazardous situation which, if not
avoided, could result in minor to moderate injury.
• NOTICE is used to address practices not related to
personal injury.
Important information
This symbol indicates important information
where there is no risk to people or property.
Additional symbols
Symbol
Explanation
▶
Step in an action sequence

Cross-reference to another part of the
document
•
List entry
–
List entry (second level)
Table 1
1.2
Safety instructions
Read all instructions before installing. Perform the steps in the
indicated sequence. Have the water heater inspected by a
trained service technician at least once every year. Failure to
comply with these instructions can result in severe, possibly
fatal, personal injury as well as damage to property and
equipment.
Installation and servicing
▶ Risk of fire when soldering and brazing!
Take appropriate protective measures when soldering and
brazing around combustible and flammable material.
▶ Ensure that only a licensed contractor installs or services
the water heater.
▶ On hot components use only material with adequate
temperature stability.
Installation and commissioning
▶ In the Commonwealth of Massachusetts, the water heater
must be installed by a licensed plumber.
▶ Do not install this device in rooms with a high moisture level
(e.g. bathrooms, saunas).
Function
▶ To ensure that the water heater functions properly, follow
these installation and maintenance instructions.
▶ Never close the blow-off line of the T&P safety valve. For
safety reasons, water may escape during heating.
If you smell gas
▶ Turn off the gas shut-off valve.
▶ Open windows and doors.
▶ Do not try to light the appliance.
▶ Do not touch any electrical switch, telephone, and do not
use outlets.
▶ Extinguish all open flames. Do not smoke! Do not use
lighters!
▶ Warn all occupants of the building. Do not ring doorbells!
▶ If you can hear gas leaking, leave the building immediately.
▶ Prevent others from entering the building and notify the
police and fire department from outside the building.
▶ From outside the building, call the gas utility company and
a trained and certified installer.
If you smell flue gas
▶ Switch off the appliance.
▶ Open windows and doors.
▶ Inform a trained and certified installer.
520 PN
6 720 644 947 (2014/11)
4 | Key to symbols and safety instructions
Insufficient ventilation may cause toxic flue gas to escape.
Risk of poisoning.
▶ Never close off or reduce the size of the air intake and outlet
openings.
▶ The appliance must not be operated until any obstructions
have been removed.
▶ Inform the system operator in writing of the problem and
the associated dangers.
Danger from escaping flue gases
▶ Ensure all vent pipes and chimneys are not damaged or
blocked.
▶ Connect only one appliance to each vent system or
chimney liner.
▶ The venting system piping must not feed into another air
extraction duct.
▶ Do not route the flue system piping through or inside
another air extraction duct.
Danger of explosion of flammable gases
▶ Work on gas components may only be carried out by a
trained and certified installer.
▶ Installation, gas and flue connection, initial commissioning,
electrical connections and annual maintenance must only
be carried out by a trained and certified installer.
Combustion air
▶ Keep the combustion air free of corrosive substances
(halogenated hydrocarbons that contain chlorine or
fluorine compounds).
Never shut off safety valves!
▶ Water may escape from the safety valve at any time when
the water is being heated.
inspection/maintenance
▶ servicing and repairs may only be carried out by a trained
and certified installer.
▶ immediately correct all faults to prevent system damage.
▶ use only bosch spare parts! damage caused by the use of
parts not supplied by bosch may void the warranty.
instruct the customer
▶ explain to the customer how the appliance works and how
to operate it.
▶ inform the customer that he/she must not carry out any
alterations or repairs.
6 720 644 947 (2014/11)
Danger from electric shock
▶ Ensure that only an authorized contractor performs
electrical work.
▶ Before performing electrical work, disconnect the power
and secure the unit against unintentional reconnection.
▶ Ensure the system has been disconnected from the power
supply.
Risk of scalding at the hot water draw-off point
▶ When the water heater is in operation, temperatures in
excess of 122 °F (50 °C) can occur. To limit the
temperature at the tap, install a thermostatic DHW mixing
valve.
▶ Water heated for washing the laundry, dishes and for other
cleaning purposes can cause scalding and permanent
injuries.
▶ Children, elderly, and handicapped persons are more likely
to be permanently injured by hot water. Never leave such
individuals in the tub or shower unattended under any
circumstances. Children must not be allowed to operate
hot water faucets themselves or to fill a bathtub.
▶ If the building has occupants in the above groups who
operate hot water faucets, or state laws / local ordinances
stipulate specific water temperatures, take the following
precautions:
– Use the lowest possible temperature setting.
– To prevent scalding, install a tempering device, such as
an automatic mixing valve, at hot water tap or water
heater. Select and install the automatic mixing valve in
accordance with the valve manufacturer's
recommendations and instructions.
▶ Water exiting from drain valves can be extremely hot. To
avoid injuries:
– Check that all connections are tight.
– Direct exiting water away from people.
▶ Measures must be taken to protect against excessive
temperature and pressure! Installation of a T&P safety
valve is required.
To protect against corrosion and ensure compliance with the
rules for electrical safety, observe the following points:
▶ Use metal fittings for potable water heating systems with
plastic piping.
▶ Use only original accessories from the manufacturer.
▶ When installation of the water heater is complete, inspect
the ground conductor (including metal fittings).
520 PN
Key to symbols and safety instructions | 5
Maintenance
Customers are advised to:
▶ Sign a maintenance and inspection contract with an
authorized contractor. Inspect and maintain the water
heater as necessary and on a yearly basis. Service as
needed.
▶ Use only genuine spare parts.
Flooding
▶ After a flood, do not use the appliance if any part has been
submerged. Damage to appliances that have been
submerged can be quite severe and pose numerous safety
risks.
▶ Every appliance that has been submerged must be
replaced.
For your safety
▶ Do not store or use gasoline or other flammable,
combustible or corrosive vapors and liquids in the vicinity
of this or any other appliance.
DANGER: Fatal accidents!
Carbon monoxide poisoning.
▶ Carefully plan where you install the
heater. Correct combustion air supply
and flue pipe installation are very
important. If a gas appliance is not
installed correctly, fatal accidents can
result such as carbon monoxide
poisoning or fire.
DANGER:
Carbon monoxide poisoning.
▶ Exhaust gas must be vented to outside
using approved vent material. See
table 5, page 15 (In Canada use only
ULCS636 approved material). Vent and
combustion air connector piping must
be sealed gas-tight to prevent flue gas
spillage, carbon monoxide emissions
and risk of fire, resulting in severe
personal injury or death. Approved vent
terminations must be used when
penetrating to the outside.
520 PN
DANGER: Electric shock!
▶ Field wiring connections and electrical
grounding must comply with local
codes, or in the absence of local codes,
with the latest edition of the National
Electric Code, ANSI/NFPA 70, or in
Canada, all electrical wiring must
comply with the local codes and the
Canadian Electrical Code, CSA C22.1
Part 1.
DANGER: Electric shock!
Shock hazard: line voltage is present.
▶ Before servicing the water heater,
unplug power supply cord from outlet.
Failure to do so could result in severe
personal injury or death.
WARNING: Damage to the appliance from
over pressure.
▶ The heater must be disconnected from
the gas supply piping system during any
pressure testing of that system at test
pressures equal to or more than 0.5 psi.
NOTICE:
▶ The appliance should be located in an
area where leakage of the heater or
connections will not result in damage to
the area adjacent to the appliance or to
lower floors of the structure. When such
locations cannot be avoided, it is
recommended that a suitable drain pan,
adequately drained, be installed under
the appliance. The pan must not restrict
combustion air flow.
WARNING:
▶ The maximum inlet gas pressure must
not exceed the value specified by the
manufacturer and the minimum value
listed is for the purpose of input
adjustment.
6 720 644 947 (2014/11)
6 | Warning
NOTICE:
▶ If a water heater is installed in a closed
water supply system, such as one
having a backflow preventer in the cold
water supply line, means shall be
provided to control thermal expansion.
Contact the water supplier or local
plumbing inspector on how to control
this situation.
WARNING: System damage!
▶ If a relief valve discharges periodically,
this may be due to thermal expansion in
a closed water supply system. Contact
the water supplier or local plumbing
inspector on how to correct this
situation. Do not plug the relief valve.
WARNING: Property damage!
▶ If the water heater is used in a space
heating application, all piping and
components connected to the water
heater must be suitable for use with
potable water.
WARNING: Fire danger!
▶ Keep appliance area clear and free from
combustible materials, gasoline and
other flammable vapors and liquids.
NOTICE:
▶ Do not obstruct the flow of combustion
and ventilation air.
WARNING: Personal Injury from toxic
chemicals.
▶ Toxic chemicals, such as those used for
boiler treatment, shall not be
introduced into the potable water used
for space heating.
NOTICE: Appliance malfunction!
▶ If power is lost while appliance is
operating. Turn off both water and
power for 15 seconds to reset device.
WARNING: Risk of scalding and property
damage.
▶ Precautions must be taken prior to
manually operating the relief valve to
avoid contact with hot water discharged
from the relief valve and to prevent
water damage.
NOTICE: Appliance damage!
▶ Label all wires prior to disconnection
when servicing controls. Wiring errors
can result in improper and dangerous
operation. Verify proper operation after
servicing.
6 720 644 947 (2014/11)
WARNING: Personal Injury from toxic
chemicals.
▶ A water heater which will be used to
supply potable water shall not be
connected to any heating system or
component(s) previously used with a
nonpotable water heating appliance.
2
Warning
WARNING:
▶ The heater must be isolated from the
gas supply piping system during any
pressure testing of that system at test
pressures equal to or more than 0.5
psig.
520 PN
Appliance details | 7
•
CAUTION:
▶ Any changes or modifications not
expressly approved by the party
responsible for compliance could void
the user’s authority to operate the
equipment.
Freeze prevention kit (7709003775)1)
Safety devices
• Flame failure device (ionization flame rod sensor)
• Pressure relief valve (Available as accessory)
• Over heat prevention (temperature limiter)
Capacity
Maximum output
BTU/hr
91 525 Btu/hr
Maximum input
BTU/hr
117 000 Btu/hr
%
> 78%
BTU/hr
30 735 Btu/hr
inches
½ ” NPT
Thermal efficiency
(Efficiency in %)
Minimum Input
Gas Requirement
Gas connection
Inlet gas pressure under maximum operation1)
Propane
water
column
10.5” - 14”
Natural Gas
water
column
5.7” - 14”
Hot water connection
inches
½ ” NPT
Cold water connection
inches
½ ” NPT
GPM (l/
min)
PSI (bar)
0.5 (1.9)
Water
Minimum water flow
Minimum recommended
water pressure
30 PSI (2.07 bar)
Water valve material
Fibreglass reinforced
polyamide (PA)
Connections:
Bottom of heater
Dimensions
Fig. 1
3
Appliance details
3.1
520 PN specifications (Technical data)
Depth
inches
(mm)
8.66” (220 mm)
Width
inches
(mm)
16.73” (425 mm)
Table 2
Approved in US/Canada
Capacity
520 PN: 4.3 GPM
Accessories (Bosch part #)
• Pressure relief valve (FWL-2)
520 PN
1) The freeze prevention kit is designed to provide protection
for the water heater down to approximately 5°F for short
term conditions only. It will not protect the appliance in
areas where the temperature is routinely expected to be
below freezing.
- The freeze prevention kit will not protect plumbing outside the
appliance from freezing. Precautions should be taken.
6 720 644 947 (2014/11)
8 | Appliance details
Height
inches
(mm)
Weight
25.75” (655 mm)
pounds (kg) 35 pounds (16 kg)
Gas types
Natural Gas
LP Gas
Venting
Natural Draft
Minimum height
feet
6* with no elbows
inches
5”
Vertical termination
Vent diameter
Sidewall termination only with AQ4 power vent kit
Table 2
1) To measure Gas Pressure, see Measuring Gas Pressure,
chapter 4.8, page 19.
3.2
Unpacking the 520PN heater
This heater is packed securely.
Before installing the unit, be certain you have the correct
heater for your type of Gas - Propane or Natural Gas.
Identification labels are found on the shipping box, and on the
rating plate which is located on the right side panel of the cover.
The 5520 PN is not approved or designed for:
• Manufactured (mobile) homes, RV's or boats
• Heating or other recirculating/pumping applications*
• Solar/preheat backup or high temperature booster use
• Installation in a bathroom or other occupied rooms
normally kept closed.
*This includes domestic hot water circulator pump loop
systems that may be installed in home hot water system prior to
installing this unit. An approved recirculation design can be
found in chapter 4.10. Contact Bosch Water Heating if further
instruction is needed.
3.3
General rules to follow for safe operation
1. You should follow these instructions when you install your
heater. In the United States: The installation must conform with
local codes or, in the absence of local codes, the National Fuel
Gas Code ANSI Z223.1/NFPA 54.
In Canada: The Installation should conform with CGA
B149.(1,2) INSTALLATION CODES and /or local installation
codes.
2. Carefully plan where you install the heater. Proper
clearances must be followed.
3. The appliance must be isolated from the gas supply piping
system by closing its individual manual gas shutoff valve (not
supplied with heater) during any pressure testing at pressures
in excess of ½ Psig (3.5 kPa).
The appliance and its gas connection must be leak tested
before placing the appliance in operation.
4. Keep water heater area clear and free from combustibles
and flammable liquids. Do not locate the heater over any
material which might burn.
5. Correct gas pressure is critical for the optimum operation
of this heater. Gas piping must be sized to provide the required
pressure at the maximum output of the heater, while all the
other gas appliances are in operation. Check with your local gas
supplier, and see chapter 4.7 and 4.8 to verify proper gas line
sizing.
Fig. 2
Rating plate
[A] Serial number
[B] Type of gas
The box includes:
• Mounting screws
• Product registration card
• Installation manual
• Incandescent particle tray
Do not lose this manual, there is a charge for a replacement.
Please complete and return the enclosed product registration
card.
6 720 644 947 (2014/11)
6. Should overheating occur or the gas supply fail to shut off,
turn off the gas supply at the manual gas shut off valve, on the
gas line. Note: manual gas shutoff valve is not supplied with the
heater.
7. Do not use this appliance if any part has been underwater.
Immediately call a qualified service technician to inspect the
appliance and to replace any part of the control system and any
gas control which has been underwater.
BOSCH is constantly improving its products,
therefore specifications are subject to
change without prior notice.
520 PN
Appliance details | 9
3.4
Dimensions and installation clearances
Fig. 3
[4]
[5]
[10]
[11]
[20]
[26]
[36]
Dimensions in Inches and (mm)
[37] Hole for fixing to wall
[38] Exhaust pipe to connector
[39] Draft diverter with flue gas monitor
[40] Gas valve
[49] Observation window
[102]Piezo
Heat exchanger
Burner
Temperature control
Water valve
Gas connection
Output control
Front cover
Dimensions
inches (mm)
520 PN
Table 3
520 PN
A
B
16.73”
25.75”
(425)
(655)
Dimensions in inches (mm)
C
D
E
F
G
H
13.15”
(334)
5.11”
(130)
21.25”
(540)
2.55”
(65)
1.18”
(30)
3/4”
6 720 644 947 (2014/11)
10 | Installation instructions
▶ 2. The hot water lines should be kept short to save energy.
Centrally locating the water heater is best. It is always best
to have hot water lines insulated.
WARNING:
The water in this water heater is cold and
always remains cold except for the times
that hot water is being used. DO NOT
INSTALL IN AN AREA WHERE IT COULD
FREEZE.
Fig. 4
Minimum clearances
Model 520PN
TOP (A)
12 inches (306 mm)
FRONT (B)
4 inches (100 mm)
BACK
0 inches
SIDES
4 inches (100mm)
BOTTOM (C)
12 inches (306 mm)
Table 4
4
Installation instructions
4.1
Introduction
Please follow these instructions. Failure to follow instructions
may result in:
• Damage or injury.
• Improper operation.
• Loss of warranty.
If you are unable to perform the tasks required to install this
heater properly, please contact a locally licensed plumber or
gas technician.
Please contact Bosch Water Heating with any questions.
4.2
Proper location for installing your heater
Carefully select the location of the water heater. For your safety
and for proper heater operation, you must provide combustion
air to the heater and a proper exhaust vent system.
▶ Drain the heater entirely if freezing
temperatures are anticipated in area
where heater is installed. See chapter
5.5 for draining instructions.
To prevent freeze damage from residual
water in the heater, introduce short
bursts of compressed air (20-40psi)
through these connections to remove
the residual water in the horizontal
pipes and water valve.
WARNING:
▶ Flammable materials, gasoline,
pressurized containers, or any other
items or articles that are potential fire
hazards must NOT be placed on or
adjacent to the heater. The appliance
area must be kept free of all combustible
materials, gasoline and other flammable
vapors and liquids.
WARNING:
▶ The heater must be isolated from the
gas supply piping system during any
pressure testing of that system at test
pressures equal to or more than 0.5
psig.
WARNING:
▶ Place the heater in a location where
water leaks will do NO DAMAGE to
adjacent areas.
▶ 1. Locate the heater where venting, gas and plumbing
connections are feasible and convenient.
6 720 644 947 (2014/11)
520 PN
Installation instructions | 11
4.3
Heater placement and clearances
The 520 PN is design certified for installation on a combustible
wall (see 4.4 Mounting installation) provided the wall is not
covered with carpet or other fabric material. For installations in
an alcove or closet, maintain the minimum clearances to
combustible and non-combustible materials listed below. See
also Fig. 4.
A. Top 12 inches (306 mm)
B. Front 4 inches (100 mm)
C. Back 0 inches
D. Sides 4 inches (100 mm)
E. Bottom 12 inches (306 mm)
4.4
Mounting Heater
WARNING: before starting installation:
▶ check that there are no loose parts
inside the appliance
▶ ensure that gas pipe, gas valve, and
burner have no damage and are
properly fitted.
▶ Read chapter 3.2 to verify proper gas
type and to check all parts are included
in box.
Front cover should be removed in order to
inspect components visually (see
instructions below).
▶ Install incandenscent particle tray using screws provided
as shown in Fig. 5.
Fig. 5
Incandescent particle tray illustration
[1] Screws
[2] Incandescent particle tray
Mounting heater.
The 520 PN is design certified for mounting on a wall.
WARNING:
▶ Do not install this appliance on a
carpeted wall.
The heater must be mounted on a wall using appropriate
anchoring materials. If wall is a stud wall sheathed with
plasterboard, it is recommended that support board(s), either
1x4’s or 1/2" (minimum) plywood first be attached across a
pair of studs and then the heater should be attached to the
support boards, see Fig. 7.
▶ Secure the two included L shaped hooks to wall studs or
support board 13 1/4” apart. (See Fig. 7).
▶ Hang heater on two L shaped hooks. (See Fig. 8).
Remove cover and inspect.
▶ Remove the temperature control.
▶ Unscrew the cover fixing screws, see Fig. 6.
▶ Remove the outer case by sliding it forwards and then
lifting upwards.
▶ Ensure that the flue terminal is clear.
▶ After inspection, replace front cover and tighten screws.
Install incandescent particle tray.
Fig. 6
520 PN
Remove front cover
6 720 644 947 (2014/11)
12 | Installation instructions
1
2
3
Fig. 7
Support board
[1] Wall studs
[2] Support board
[3] 1”x4” Space board
unit. When all requirements are followed, the unit will
operate properly and safely. However, there may still be a
risk of freezing due to negative draft if all the combustion
appliances in the building or structure are not being
supplied with a sufficient amount of make-up air. A wood
stove or furnace can pull outside air down through the
BOSCH vent pipe and across the heat exchanger tubing. If
the air is cold enough, the heat exchanger is at risk of
freezing and bursting. Supplying more combustion air for
all combustion appliances is the solution. Follow the
instruction on venting and checking the adequacy of make
up air. A HVAC specialist should be consulted on how to
provide more combustion air if necessary. Observe the
following instructions concerning combustion air.
Appliances located in unconfined spaces:
a) An unconfined space is one whose volume is greater than 50
cubic feet per 1000 Btu per hour of the combined rating of all
appliances installed in the space. That would be 5850 cubic
feet for the BOSCH 520 PN alone.
b) Installations in structures that have been tightly constructed
(air infiltration rate of 0.40 ACH or less) must be provided for
combustion air per the National Fuel Gas Code. Consult a HVAC
specialist if your air infiltration rate is questionable.
Appliances located in confined spaces:
The confined space must be provided with two permanent
openings, one commencing within 12 inches of the top and one
commencing within 12 inches of the bottom of the enclosure.
Each opening must have a minimum free area of one square
inch per:
•
•
•
1000 Btu/hr if all air is taken from inside the building.
2000 Btu/hr if all air is taken from the outside by horizontal
ducts.
4000 Btu/hr if all air is taken from the outside by direct
openings or vertical ducts.
Or the confined space must be provided with one permanent
opening or duct that is within 12 inches of the ceiling of the
enclosure. This opening must have a minimum free area of one
square inch per:
•
Fig. 8
4.5
Secure heater to wall
Combustion air requirements
The BOSCH water heater holds cold water in its copper heat
exchanger and water valve when not in use. Because of
this, any cold air that comes down through the unit's vent
pipe is capable of freezing these components. This
Installation Manual specifies the minimum vertical vent
pipe and the amount of combustion air required for this
6 720 644 947 (2014/11)
3000 Btu/hr if all air is taken from the outside by a direct
opening or vertical duct.
Louvers, grills and screens have a blocking effect. If the
effective free area is not known, increase the sizes of your
openings by 400% if your louvers are wood and by 135% if your
louvers are metal. Refer to the National Fuel Gas Code for
complete information. In buildings of tight construction all air
should be taken from outside.
520 PN
Installation instructions | 13
4.6
Venting
DANGER:
▶ Do not reduce the vent pipe size. Do not
put an elbow directly on top of heater.
Failure to follow venting requirements
may cause dangerous exhaust gases to
enter living space.
▶ Minimum vent pipe diameter: 5 inches
▶ Minimum vertical vent height: 6 feet, with no elbows
▶ Establish 12 inch rise before any elbow
The heater must be vented to the outside following all local
ordinances and specifications for installing a gas appliance
vent or chimney. The heater must be located as close as
practicable to a vertically rising chimney or vent that has a
listed vent cap at its termination point. The venting system
must be designed and constructed so as to develop a positive
flow adequate to remove flue gasses to the outdoors. Consult
the National Fuel Gas Code if the vent will have elbows or share
venting with another natural draft appliance.
WARNING:
▶ Do not combination vent with a
mechanically vented appliance.
4.6.1 Horizontal venting
WARNING:
▶ Horizontally venting to a vertically
constructed vent stack along an outside
wall of a building is not permissible.
▶ An approved gas vent connector must be attached to the
top of the water heater and rise vertically at least 12"
before entering into an approved gas vent connector
elbow.
▶ The minimum vertical gas vent height allowed is 6 feet;
horizontal vent connectors and elbows are not to be
considered in the total gas vent height.
▶ All gas vent sections must be secured to each other with
sheet metal screws and be properly supported.
Horizontal runs:
Any gas vent section that is greater than 45 degrees from the
vertical is considered horizontal. Horizontal sections must
slope upwards at least ¼ inch for every foot of its horizontal
length and be properly supported. Keep the horizontal section
short and avoid too many elbows. The maximum horizontal run
allowed is half of the total vertical vent height; horizontal vent
connectors and elbows are not to be considered in the total gas
vent height.
Vent termination:
The gas vent constructed of double wall Type B gas vent must
terminate above the roof surface with a listed vent cap at a
height that's in accordance with Fig. 11 and table 2, provided
it is at least 8 feet (2.4 m) from a vertical wall or similar
obstruction. All other gas vents that are not able to terminate
within the minimum specified height allowed must terminate
not less than 2 feet (0.6 m) above the highest point where it's
passed through the roof and at least 2 feet (0.6 m) higher than
any vertical wall or similar obstruction within 10 feet (3.1 m).
WARNING:
▶ Horizontally venting to a sidewall vent
terminator (without power vent) is not
permissible.
A power vent, with a proof-of-draft safety interlock device, is
required and is available for sidewall venting. Contact your
dealer. In the Commonwealth of Massachusetts power vented
applications must utilize proof-of-draft safety interlock device.
4.6.2 Vertical venting
▶ A 5 inch diameter gas vent constructed of double wall Type
B gas vent is recommended. A 6 inch vent is required in
elevations greater than 2000 feet, see Fig. 10. Under no
circumstances should the vent pipe be reduced in size.
520 PN
6 720 644 947 (2014/11)
14 | Installation instructions
Commonwealth of Massachusetts requires the use of a listed
liner. Lining systems include approved clay flue lining, a listed
chimney lining system or other approved material that will
resist corrosion, erosion, softening, or cracking from exhaust
flue gases at temperatures up to 1800 degrees F. The lining
system must be listed for use with naturally drafting, draft hood
equipped gas appliances. Follow local codes and refer to NFGC
54 and NFPA 58.
Existing interior masonry chimney
The metal gas vent pipe should be permanently mounted inside
the masonry chimney. Double wall Type B gas vent is
recommended. The masonry chimney may have to be tile or
metal lined before the insertion of the gas vent pipe; check local
codes for clarification. The lining material must be listed for use
only with naturally drafting, draft hood equipped gas
appliances. Follow manufactures instructions for installation of
listed lining material. You may not vent any other fuel burning
appliances into any free space remaining in the chimney. The
minimum vertical gas vent length within the masonry chimney
should be no less than 6 ft (1.8 m); the vent terminator should
extend at least 3 feet (0.9 m) above where the chimney meets
the roofline and at least 2 feet (0.6 m) higher than any vertical
wall or similar obstruction within 10 feet (3.1 m). The top of the
gas vent should have an approved vent terminator. See Fig.
12.
ESTABLISH A ONE
FOOT RISE BEFORE
ANY ELBOWS
Fig. 9
Flat roof
[1] Listed vent cap
[3] Listed gas vent
[A] Minimum 6 feet (1,8m)
5” X 6” ADAPTOR
USED ON HIGH
ALTITUDE
Fig. 10
Vent Adaptor for High Altitude Installations
Masonry chimney
Masonry chimneys shall be built and installed in accordance
with NFPS 211 or local codes. A minimum 4" diameter gas vent
pipe (metal double wall Type B), or an approved clay flue liner
or a listed chimney lining system must be used when venting
into a naturally drafting, internal masonry chimney. Local
codes may require the use of both gas vent and an approved
lining system when venting into a masonry chimney. The
6 720 644 947 (2014/11)
520 PN
Installation instructions | 15
ESTABLISH A
ONE
FOOT RISE
Fig. 11
Pitch roof
[1]
[2]
[3]
[H]
Listed vent cap
Lowest discharge opening
Listed gas vent
H (minimum) height from roof to lowest discharge
opening
[X] Roof pitch is X/12
[A] Minimum 6 feet (1,8m)
GAS VENT TERMINATIONS FOR LISTED VENT CAPS
Roof pitch
H (minimum) feet
meters
Flat to 6/12
1.0
0.30
6/12 to 7/12
1.25
0.38
Over 7/12 to 8/12
1.5
0.46
Over 8/12 to 9/12
2.0
0.61
Over 9/12 to 10/12
2.5
0.76
Over 10/12 to 11/12
3.25
0.99
Over 11/12 to 12/12
4.0
1.22
Over 12/12 to 14/12
5.0
1.52
Over 14/12 to 16/12
6.0
1.83
Over 16/12 to 18/12
7.0
2.13
Over 18/12 to 20/12
7.5
2.27
Over 20/12 to 21/12
8.0
2.44
Fig. 12
[1]
[2]
[3]
[A]
4.7
Masonry chimney
Listed vent cap
Vent connector
Establish a one foot rise before any elbows
Gas vent
Gas piping & connections
Before connecting the gas supply, check the rating plate on the
right side of the heater to be sure that the heater is rated for the
same gas to which it will be connected.
In the United States: The installation must conform with local
codes or, in the absence of local codes, the National Fuel Gas
Code ANSI Z223.1/NFPA 54.
In Canada: The Installation should conform to CGA B149
INSTALLATION CODES and/or local installation codes.
Mount regulator to gas inlet pipe as shown in Fig. 13. The arrow
on the back of the regulator indicates the direction of gas flow
and should point toward the appliance.
Table 5
520 PN
6 720 644 947 (2014/11)
16 | Installation instructions
Bubbles are a sign of a leak. A combustible gas detector may
also be used to detect for leaks.
DANGER:
▶ If you have a leak, shut off the gas.
Tighten appropriate fittings to stop leak.
Turn the gas on and check again with a
gas leak detection solution. Never test
for gas leaks using a match or flame.
Fig. 13
Installation of Gas Pressure Regulator
Note: The 520 PN comes with a gas pressure regulator. Failure
to install or altering the gas pressure regulator will be a violation
of CSA certification of the unit. The regulator supplied with the
heater is preset for the gas shown on the rating plate to the
correct pressure. It is an appliance level regulator designed for
(low inlet) pressure (less than 1/2 Psig or 14" W.C.).
WARNING: DO NOT connect to an
unregulated or high pressure propane line
or to a high pressure commercial natural gas
line.
WARNING: The heater must be isolated
from the gas supply piping system during
any pressure testing of that system at test
pressures equal to or more than 0.5 psig. If
overpressure has occurred, such as through
improper testing of the gas lines or
malfunction of the supply system, the gas
valve must be checked for safe operation.
GAS CONNECTIONS
▶ Install a manual gas shut off valve, on the gas supply line.
▶ Install a union when connecting gas supply.
▶ Attach the appliance regulator to the inlet gas pipe.
▶ The minimum diameter required for any appliance
connector used is ¾”.
▶ National Fuel Gas Code requires that a sediment trap (drip
leg) be installed on gas appliances not so equipped. The
drip leg must be accessible and not subject to freezing
conditions. Install in accordance with the
recommendations of the serving gas supplier.
HIGH ALTITUDE INSTALLATION
The pressure regulator provided with the heater is adjusted to
deliver the proper gas pressure (as indicated on the rating plate
and in the manual for altitude up to 2000 feet (660 meters)
above sea level. On appliances being installed above 2000 ft
(660 meters) elevation, the inlet gas pressure should be set at
installation to the value shown below.
Note: The gas pressures specified below refer to pressures
taken at the pressure tap on the gas inlet pipe just above the
regulator. See chapter 4.8 for measuring gas pressure.
MAXIMUM INLET GAS FLOW PRESSURE SETTING
Nat. Gas inches
Liquid Propane
Altitude
W.C.
inches W.C.
0’ - 2 000 ft
5.7”
10.5”
2 000 ft - 4 500 ft
Table 6
4.6”
8.4”
Above 4.500 ft consult your local gas provider
GAS LINE SIZING
The gas supply piping should be sized according to the
applicable code for a maximum draw of 117,000 BTUH.
Measure the length of gas supply line and use the tables in Fig.
14 or the gas line manufacturer’s sizing tables to determine the
pipe diameter necessary to accommodate the BTU demand of
the unit. If there are more gas appliances drawing on the same
line, size the gas line according to the total maximum amount of
BTU draw for all appliances.
Note: Under sizing the gas line may result in diminished output
and improper operation. See chapter 4.8 for the procedure to
confirm gas pressure.
When connections are made, check for gas leaks at all joints.
Apply some gas leak detection solution to all gas fittings.
6 720 644 947 (2014/11)
520 PN
Installation instructions | 17
FOR NATURAL GAS
Maximum Capacity of pipe in Cubic Feet of Gas per Hour for Gas Pressure of 0.5 Psig or less and a Pressure drop of 0.3 in Water
Column (0.75mbar).(Based on a 0.60 Specific Gravity Gas) Btu numbers given in thousands. Copper tubing is prohibited for use
with Natural Gas in the Commonwealth of Massachusetts and not recommended elsewhere.
Follow boxed numbers for piping just one 520 PN (example: ¾” B.I. Natural Gas pipe for 20 ft (6.1m). will handle 190,000 btu’s
(55.7 kWh). For multiple appliances combine the total btu input load and then refer to applicable chart below.
Lenght of Black Iron Pipe, Feet
Nominal
Iron
Pipe
3/4
Internal
Diameter
inches
0.824
10
20
30
40
50
60
70
80
90
100
125
150
175
200
278
190
152
130
115
105
96
90
84
79
72
64
59
55
1
1.049
520
350
285
245
215
195
180
170
160
150
130
120
110
100
1 - 1/4
1.380
1050 730
590
500
440
400
370
350
320
305
275
250
225
210
Table 7
Tube
size,
Inches
Length of Flexible Corrugated Stainless Steel Tubing (CSST), Feet
20
30
40
50
60
1/2
EHD*
18
10
82
58
47
41
37
34
3/4
23
161
116
96
83
75
68
1
30
330
231
188
162
144
131
1 - 1/4
37
639
456
374
325
292
267
Table 8
* EHD = Equivalent Hydraulic Diameter. The greater the value EHD, the greater the gas capacity of the tubing.
520 PN
6 720 644 947 (2014/11)
18 | Installation instructions
FOR LP GAS
Maximum Capatity of Pipe in Thousands of BTU per Hour of Undiluted Petroleum Gases (at 11 inches Water Column Inlet Pressure)
(Based on a Pressure Drop of 0.5 Inch Water Column).
Length of Flexible Corrugated Stainless Steel Tubing (CSST), Feet
Tube size
inches
20
30
40
50
60
1/2
EHD*
18
10
129
91
74
64
58
53
3/4
23
254
183
151
131
118
107
1
30
521
365
297
256
227
207
1 - 1/4
37
971
661
528
449
397
359
Table 9
* EHD = Equivalent Hydraulic Diameter. The greater the value EHD, the greater the gas capacity of the tubing.
Nominal
Iron Pipe
Size
inches
Black Iron Pipe
Lenght of pipe, Feet
20
30
40
50
60
80
100
125
150
200
1/2
10
291
200
160
137
122
110
94
84
74
67
58
3/4
608
418
336
287
255
231
197
175
155
140
120
1
1145
787
632
541
480
434
372
330
292
265
227
Table 10
Cooper (LP gas only)
Length of Tubing, feet
Outside
diameter
Inch
20
30
40
50
60
70
80
90
100
3/8
10
39
26
21
19
-
-
-
-
-
-
1/2
92
62
50
41
37
35
31
29
27
26
5/8
199
131
107
90
79
72
67
62
59
55
3/4
329
216
181
145
131
121
112
104
95
90
Table 11
Maximum Capacity of Semi-Rigid copper Tubing in Thousands of BTU per Hour of Undiluted Liquefied Petroleum Gases (at 11
inches Water Column Inlet Pressure).
(Based on a Pressure Drop of 0,5 inch Water Column).
* Source National Fuel Gas Code NFPA 54, ANSI Z223.1
- No Additional Allowance is necessary for an ordinary number of fittings.
6 720 644 947 (2014/11)
520 PN
Installation instructions | 19
4.8
Measuring gas pressure
Connecting manometer
▶ Shut off gas.
▶ Remove front cover and locate inlet gas pressure
measuring point on the right side, see Fig. 14.
▶ Loosen screw from test point on the right side and connect
manometer tube on test point.
4.9
Water connections
When facing the heater, the ½ ” cold water inlet is on the bottom
right and the hot water outlet is on the bottom left.
▶ Install unions or the Webstone service valves when
connecting plumbing to the water heater. This will
facilitate any necessary cleaning and servicing.
Although water piping throughout your structure may be other
than copper, we recommend that copper piping or suitably
rated stainless steel flex line piping be used for at least three
feet before and after the heater (follow local codes if more
stringent). Never sweat any rigid piping directly to or beneath
the water connections, damage can occur to the internal water
valve from heating of the pipe. Plastics or other PEX type
plumbing line materials are not recommended for connecting
directly to the water heater. Keep water inlet and outlet pipes to
no less than ½" (12.7mm) diameter to allow the full flow
capacity.
It is recommended that all water piping below the heater be
properly insulated to avoid heat loss.
If the cold and hot connections to the heater are reversed, the
heater will not function. Be certain there are no loose particles
or dirt in the piping. Blow out or flush the lines before
connecting to the water heater. Full port valves should be
installed on both the cold water supply and hot water outlet
lines to facilitate servicing the heater (see Fig. 16). For
installation on a private well system with the use of a pressure
tank, the lowest pressure range setting recommended is 30-50
psi (2.07 and 3.45bar).
Fig. 14
Gas pressure measuring point
[A] Inlet tap
Static pressure test
▶ Turn gas supply back on.
▶ Record static gas pressure reading on back page of manual.
Operating pressure test
▶ Turn on all hot water taps served by the water heater.
▶ Run high hot water flow rate.
▶ Set flow control knob fully clockwise.
▶ Set slide control to the right.
▶ Record operating gas pressure reading on back page of
manual.
Connecting the pressure relief valve (PRV)
A listed pressure relief valve must be installed at the time of
installation. No valve is to be placed between the PRV and the
heater. No reducing coupling or other restriction may be
installed in the discharge line. The discharge line must be a
minimum of 4” above a drain and installed such that it allows
complete drainage of both the PRV and the line.
The location of the PRV must be readily accessible for servicing
or replacement, and be mounted as close to the water heater as
possible. See Fig. 15 To install the PRV, a suitable fitting
connected to an extension on a “T” fitting can be sweated to the
hot water line.
Support all piping.
Gas pressures lower than 5.7" W.C. for Natural Gas or 10.5"
W.C. for LP Gas will result in insufficient degree rise to the hot
water being used, and must be corrected. See Gas Line Sizing
under chapter 4.7.
520 PN
6 720 644 947 (2014/11)
20 | Operation instructions
5
4
2
1
3
6720608030-19.4Av
Fig. 16
[1]
[2]
[3]
[4]
[5]
Fig. 15
Plumbing connections and pressure relief valve
shown with optional Webstone service valves
4.10 Recirculation application
Since recirculation through the heater is not permissible, the
following drawing is provided to outline a proper recirculation
application using the BOSCH PRO water heater with an Ariston
minitank. This schematic is for illustration only and must not be
used for actual installation without appropriate engineering
and technical advice from a professional properly licensed in
locality where the installation is made.
Recirculation application
Full port isolation valve
Circulator
Check valve
PRV
Expansion tank
The use of a small electric mini-tank (4-6 gallon size) should be
used for this application and designed so the pump will
circulate the water through the mini-tank and the building's hot
water return loop only. A timed or thermostatically controlled
operation of the pump is commonly done. The 520 PN should
be plumbed in line before the mini-tank water heater. Contact
Bosch Water Heating if further instruction is needed.
5
Operation instructions
5.1
For your safety read before operating your
water heater
WARNING:
▶ If you do not follow these instructions
exactly, a fire or explosion may result
causing property damage, personal
injury or loss of life.
Upon initial installation, existence of air in
the gas supply line and in the water line may
cause some ignition delay. In that case,
repeat the ignition process until all the air
has been purged.
A. This appliance employs a piezo-igniter to light the pilot
burner. When lighting the pilot, follow these instructions
exactly.
B. What to do if you smell gas.
6 720 644 947 (2014/11)
520 PN
Operation instructions | 21
WHAT TO DO IF YOU SMELL GAS
▶ Close gas valve. Open windows.
▶ Do not try to light any appliance.
▶ Do not touch any electric switch; do not use any phone in
your building.
▶ Immediately call your gas supplier from a neighbors phone.
Follow the gas supplier’s instructions.
▶ If you cannot reach your gas supplier, call the fire
department.
C. Use only your hand to push in the gas control buttons. Never
use tools. If a button will not push in, check to make sure the
buttons are being pushed in the proper sequence. Follow these
instructions exactly. If control button(s) are jammed, close the
heater’s individual manual shutoff valve and call a qualified
service technician. Forced or attempted repair may result in a
fire or explosion.
D. Do not use this appliance if any part has been under water.
Immediately call a qualified service technician to inspect the
appliance and to replace any part of the control system and any
gas control which has been under water.
5.2
▶ Slide the gas valve button to the position
.
Fig. 18
▶ Fully depress gas valve button.
Lighting instructions
▶ STOP! Read the previous safety information.
▶ The gas valve must be turned off by sliding the gas valve
button to all the way to the left.
Fig. 19
▶ With the gas valve button fully depressed, light pilot by
pushing the piezo button. This step may have to be
repeated.
Fig. 17
▶ Wait five (5) minutes to clear out any gas. If you smell gas,
STOP! Follow “B” in the safety information above on this
plate. If you don’t smell gas, go to next step.
▶ The pilot burner window is located in the front center of the
cover.
Fig. 20
520 PN
6 720 644 947 (2014/11)
22 | Operation instructions
▶ Observe the pilot flame through the peephole. The gas
valve button should be held down for at least 15 seconds
with pilot burning before releasing. When the gas valve
button is released, the pilot should continue to burn.
- If the gas valve button does not pop out when released,
stop and immediately call your service technician or gas
supplier.
- If pilot does not stay lit, repeat all steps.
- If pilot will not stay lit after several tries, slide the gas valve
button all the way to the left and call service technician or
gas supplier.
▶ The heater will now fire at minimum power when water is
drawn at a rate greater than the required activation flow
rate.
Note: If main burner should fail to ignite, make sure pilot is
burning. If not, repeat lighting steps.
Note: The 520 PN operates in two modes. See SETTING THE
WATER TEMPERATURE.
5.3
To turn off appliance
▶ Slide the gas valve button all the way to the left and turn off
the installer supplied manual gas shutoff on the supply line
to the heater.
Fig. 22
Clockwise
Counterclockwise
90 °F
45 °F
Activation rate
0.5 GPM
1.1 GPM
Max flow rate
2.0 GPM
3.7 GPM
Knob position
Degree rise
Table 12 Temperature rise (slide control to the right)
As the temperature adjustment knob is turned counterclockwise, the output temperature will lower and the activation
rate will be raised. Turning the knob clockwise will raise the
temperature and lower the activation rate.
Gas control slide button
The gas control slide button adjusts temperature by adjusting
how much gas is allowed to flow to the burners.
As the slide is adjusted to the left, the output temperature will
lower, with the lowest setting being the small flame position.
Fig. 21
5.4
Setting the water temperature
The 520 PN has a gas control that modulates burner input in
response to flow. Its purpose is to ensure that the hot water
temperature will remain steady, although the water flow
demand might vary. The output temperature can be adjusted
with either the temperature adjustment knob or the gas control
slide.
Temperature adjustment knob
The temperature adjustment knob on the front bottom of the
heater (see Fig. 22) adjusts temperature by adjusting flow
capacity. See table 12 for details.
6 720 644 947 (2014/11)
Fig. 23
The hottest position is the highest flame position all the way to
the right.
520 PN
Maintenance and service | 23
6
Maintenance and service
6.1
Maintenance intervals
WARNING:
▶ Failure to perform recommended
maintenance may result in complete
failure of the unit over time.
The warranty does not cover failures
due to improper or insufficient
maintenance.
Fig. 24
5.5
Draining water from heater
If there is a risk of freezing, proceed as follows:
▶ Remove the retaining clip from threaded bushing (Fig. 25,
[pos. 1]).
▶ Remove threaded bushing (Fig. 25,[pos. 2]) from water
valve.
▶ Empty the appliance of all water.
The 520 PN requires periodic maintenance. The below time
maintenance intervals should kept the unit operating for many
years.
Every year
▶ Inspect inlet water filter screen (see chapter 6.2)
▶ Inspect pilot assembly and flame (see chapter 6.3)
▶ Inspect burner assembly (see chapter 6.4)
Every 2 years
▶ Inspect heat exchanger fins for soot, debris or blockage.
Clean if necessary (see chapter 5.5)
▶ Lubricate and clean water valve (see chapter 6.2)
Every 3 to 5 years
▶ Rebuild water valve (see chapter 6.2)
▶ Clean pilot assembly and clean or replace orifice (see
chapter 6.3)
6.2
Water valve
The water valve is the main control that tells the heater to fire.
If the periodic maintenance is neglected, more costly damage
may occur over time.
Fig. 25
Drain plug and filter location
[1] Retaining clip
[2] Threaded bushing
Inspecting inlet water filter screen
Shut off the installer supplied cold water isolation valve to the
heater. If one is not installed, install before proceeding. Open
the nearest hot water tap to drain the plumbing lines. Position
a bucket under the heater's water valve assembly to catch any
water that may drain from the heater. Remove the filter
retaining pin located at base of water valve (see Fig. 25).
Remove the threaded bushing to access the cylindrical filter
inside. Remove filter, clean with water and inspect for damage.
If the filter is at all damaged, it should be replaced.
Lubricating the water valve
A more detailed instruction is available on our website at
www.bosch-climate.us. Shut off the installer supplied cold
water isolation valve to the heater. If one is not installed, install
before proceeding. Open the nearest hot water tap to drain the
520 PN
6 720 644 947 (2014/11)
24 | Maintenance and service
plumbing lines. Position a bucket under the heater's water
valve assembly to catch any water that may drain from the
heater. Disconnect the inlet water pipe going to the back of the
water valve. Disconnect the water pipe leading out of water
valve to the heat exchanger. Do this by removing the retaining
pin on water valve assembly and pulling the pipe free from the
water valve. Loosen the two set screws at the bottom of the
water valve where it connects to the gas valve. If the set screws
are seized, STOP and call Bosch tech support before
proceeding. Forcing and snapping seized set screws may cause
irrevocable damage to the water valve and gas valve
assemblies. Remove the water valve by pulling it to the right.
Separate the two halves of the water valve by removing the five
screws on the left side of the water valve. Apply lithium or
faucet & valve grease to the pushrod and o-ring. (See Fig. 28).
Inspect the venturi and clean if necessary. (see Fig 28).
Rebuilding the water valve
Several parts within the water valve should be replaced every 3
to 5 years depending on water quality and usage. The parts list
and instructions can be found on our website at www.boschclimate.us. Failure to rebuild the water valve can result in
decreased performance or damage to the heater.
6.3
Pilot
Inspecting pilot
The pilot should burn with a clean sharp blue flame. The flame
should fully engulf the tip of the thermocouple. If it does not,
clean the pilot assembly per procedure below.
Cleaning pilot assembly
Shut off gas supply to the heater using installer supplied
manual gas shutoff. Locate pilot gas tubing mounted in the
center of the burner assembly. At the base of the pilot gas
tubing there is a retaining clip. Release pilot gas tubing from
this clip. Push upwards on other end of pilot gas tubing to
release it from burner mount. Remove brass hex headed pilot
orifice from gas valve (located near base of pilot gas tubing).
Soak orifice and pilot gas tubing in carburetor cleaner for 30
minutes. Dry off and reinsert orifice in gas valve. If heater is an
LP unit, replace orifice. Reinstall the pilot gas tubing following
removal instructions in reverse. Open gas supply and return
heater to service.
CAUTION:
▶ Do not ream or poke orifice as it will
enlarge orifice opening.
6.4
Main burners
The main burner flames should be blue, with a more intense
blue cone in the center core. Yellow flames could be a sign of
wrong size gas orifices or dirty burners, a blockage on the heat
6 720 644 947 (2014/11)
exchangers fins. If some burners have yellow flames while
others have blue flames, it is likely that dust, lint or spider webs
have partially clogged the burner venturis. To clean the
burners, contact a gas service person.
6.5
Vent assembly / heat exchanger
Inspect the draft hood and heat exchanger fins for signs of soot
build-up or any other foreign material such as spider webs.
Clean out any debris found in the vent hood and/or heat
exchanger fins. Signs of soot indicate insufficient combustion
air or exhaust draft. Check for vent assembly blockage or
combustion air blockage on the underside of the unit.
6.6
Mineral scale build-up
The 520 PN, when operated at lower temperatures settings,
does not accumulate mineral build-up. If however, the heater is
used at the higher temperature settings and the water has a
high mineral content, periodic descaling may be necessary.
The heating coils should be flushed with a descaling solution.
6.6.1 Descaling heat exchanger
1. Disconnect electrical supply from the water heater.
2. Shut off the water supply to the water heater using (installer
supplied) isolation valve.
3. Open hot water taps to drain and relieve pressure from the
plumbing system.
4. Drain water from the unit's heat exchanger by disconnecting
inlet and outlet water connections.
5. Connect the line (A) from the outlet of the circulating pump
(installer supplied) to the inlet water fitting on the water heater.
6. Using another line (B), connect to the water outlet fitting on
the water heater. Route the other end of this line into a
descaling reservoir.
7. Using a 3rd line (C) from the descaling reservoir, connect to
the inlet side of circulating pump. Verify there is a filter on the
end of the line in the descaling reservoir.
8. Make sure all connections are "hand tight"
9. Fill tank with descaling solution so lines inside are
submersed. We recommend a straight white vinegar solution. If
using a commercial descalant, refer to manufacturer's
instructions on dilution with water.
10. Operate the circulating pump.
11. Make sure there are no leaks and the solution is flowing
from the descaling reservoir through the heat exchanger and
returning to the reservoir.
12. Run solution through the heat exchanger until the solution
returning to the descaling reservoir comes out clear. (Changing
to a fresh solution may be necessary during this process).
520 PN
Troubleshooting | 25
13. Disconnect all lines and drain all solution from heat
exchanger. Properly discard of solution.
14. Position a container below the hot water outlet and connect
cold water supply. Open cold water supply isolation valve and
flush heat exchanger with clean water.
15. Shut cold water isolation valve and reconnect hot water
supply to the water heater.
16. Reconnect electrical supply to unit, open water isolation
valves, and return the unit to service.
pressure at the inlet tap (chapter 4.9). If gas is not present,
verify manufacturer supplied Maxitrol regulator is in the upright
position. The arrow on the back of the regulator should point in
the same direction as gas flow.
2. If the unit was just installed or the gas lines have been
worked on, there may be air in the gas line. Centered in the
sparking position, hold down the gas control slide button while
hitting the pilot igniter button every few seconds. It may take
several minutes to bleed air out of the gas line.
3. Verify a spark is being thrown at pilot area while gas control
slide button, centered in the single flame position, is being
firmly depressed. Repeatedly push in pilot igniter button to
light the pilot. If no spark is present, verify proper wire
connection to the electrode.
4. Pilot assembly may be blocked. Clean or replace the pilot
orifice (chapter 6.3).
7.3
Pilot lights, but goes out when button is
released
1. When lighting pilot ensure the gas control slide button is fully
depressed and held down for at least 20 seconds after pilot is
lit.
2. Verify gas type indicated in rating sticker located on right
hand side of cover, coincides with the gas type you are using.
NG is a natural gas unit and LP is for liquid propane.
3.If using a power vent, check the safety spillage switch reset
button (the safety spillage switch is wired through the water
heater's thermocouple circuit). The spill switch should be
located at top of water heater close to draft diverter (Consult
manual that came with powervent).
Fig. 26
7
Troubleshooting
7.1
Introduction
Many of the questions customers ask regarding operation of
this unit can be answered by following the troubleshooting
steps as outlined below. Visit our web site at www.boschclimate.us for more detailed troubleshooting. For best results,
perform each step before proceeding to the next. The
suggested solutions may require that the cover be taken off.
(See chapter 4.4).
7.2
Pilot does not light
1. Verify gas supply is on at Natural Gas meter or Propane Tank.
Make sure all manual gas shut off valves are in the open
position. Have licensed gas technician confirm adequate gas
520 PN
4. Check all connections of the pilot safety circuit. The pilot
safety circuit consists of a thermocouple, overheat sensor
(ECO), flue gas sensor, safety spillage switch (models with
Powervents only) and the electromagnet (See parts diagram
for locations). Clean sensor connections with light sandpaper if
corrosion is evident. The electromagnet connection is 5mm nut
from the thermocouple which screws into a larger 17mm nut.
Tighten both nuts snugly but do not over tighten.
5. Pilot flame should be blue in color and completely engulfing
the tip of the thermocouple. If not, have a licensed gas
technician verify gas pressure is in accordance with
manufacturer's specifications (chapter 4.9) and clean or
replace the pilot orifice (chapter 6.3).
6. Have a licensed gas technician verify the proper operation of
the thermocouple by measuring the millivoltage from the
thermocouple lead to ground. The proper reading should be
24mVDC or greater. If the reading is lower, the thermocouple
may be defective. Call Bosch Water Heating for further
instructions.
6 720 644 947 (2014/11)
26 | Troubleshooting
7.4
Pilot goes out during or after hot water use
1. Pilot outage during use typically results from the unit's safety
overheat/high limit sensors interrupting the pilot circuit. The
520 PN does not have a thermostat. If inlet water is preheated,
the unit will overheat, stopping the flow of gas. Plumb inlet with
a cold water line only.
4. Close installer supplied cold water shut off valve (if none
installed, install before proceeding). Open all hot water taps
supplied by the heater. Wait 5 minutes and check all taps. Any
water running is a sign of a plumbing crossover. Consult a local
plumber or service person for help in correcting a plumbing
crossover.
2. Failure to vent properly by reducing pipe diameter, improper
use of elbows or not meeting required vent length are common
causes that deactivate the pilot safety circuit. Confirm venting
is in accordance with manufacturer's specifications (see
chapter 4.7).
5. Verify flow through the water heater is sufficient. Turn
temperature adjustment knob all the way clockwise. Fully open
a hot water faucet and fill a quart container. If the container fills
in 30 seconds or less, the flow rate (1/2 gallon per minute) is
sufficient to activate the heater.
3. Confirm the combustion air requirements are being met in
accordance with manufacturer's specifications (see chapter
4.6). Proper venting and combustion air will ensure a proper
draft.
6. Inspect the water path outside of the heater for
obstructions. Make sure all outlets (i.e. showerheads, faucet
aerators and whole house filters) are clear of debris. Also, the
water heater's inlet filter screen should be inspected and
cleaned (see chapter 6.2).
4. Confirm that the burners in the water heater go off
immediately when the hot water is turned off. If they remain on
or shut down slowly, then the overheat sensor (ECO) will
interrupt the pilot circuit and shut off all gas to the heater. The
water valve assembly, which actuates the burners, may be dirty
and require periodic maintenance (every 2 - 5 years depending
on water quality and use) (see chapter 6.2).
5. Check all connections of the pilot safety circuit. The pilot
safety circuit consists of a thermocouple, overheat sensor
(ECO), flue gas sensor, safety spillage switch (models with
Powervents only) and the electromagnet (See parts diagram
for locations). Clean sensor connections with light sandpaper if
corrosion is evident. The electromagnet connection is 5mm nut
from the thermocouple which screws into a larger 17mm nut.
Tighten both nuts snugly but do not over tighten.
6. Verify pilot flame completely engulfs the thermocouple tip. If
pilot is too small, clean pilot orifice (see chapter 6.3).
7. If the water has a high mineral content, the heat exchanger
may be scaled internally. This restricts the water path, causing
the water to over heat which shuts all gas off to the heater.
Instructions for descaling the heat exchanger are available at
www.bosch-climate.us.
8. If steps 1 through 7 do not correct the problem, then confirm
that the gas pressure is adequate. Ensure gas pressure is in
accordance with manufacturer's specifications (see
chapter 4.9). A gas pressure reading is needed to proceed
further. Contact your original installer or a licensed gas
technician to obtain this reading.
7.5
Burners do not light with water flow
1. Verify the pilot is lit.
2. Verify the gas control slide button is in middle position.
3. Verify the cold water supply is connected to the right side of
the heater.
6 720 644 947 (2014/11)
7. The water valve assembly, which actuates the burners,
requires periodic maintenance (every 2 - 5 years depending on
water quality and use) (see chapter 6.2).
7.6
Hot water temperature fluctuates at tap
1. Close off installer supplied cold water shut off valve (if none
installed, install before proceeding). Open all hot water taps
supplied by the heater. Wait 5 minutes and check all taps.
Water running is a sign of a plumbing cross-over. Consult a local
plumber or service person for help in correcting a plumbing
crossover.
2. Check for a clogged inlet water filter screen (see
chapter 6.2).
3. Hot water is very hot out of the tap, requiring a lot of cold
water to be added with it in order to attain a usable hot water
temperature. The addition of too much cold will overpower and
slow the flow within the tankless water heater, decreasing it
below activation point, which shuts off the burners. The end
result is nothing but cold water coming out of the outlet.
Reduce the need for cold water mix by setting the gas slide
control button towards the single flame position for lower hot
water temperatures. If the problem persists, go to www.boschclimate.us for a more detailed service bulletin on this problem.
4. The 520 PN is designed to modulate gas flow to the burners
when water flow varies. If the water pressure in the home is
erratic and the water flow is not consistent while a tap is
opened, then the temperature of hot water will fluctuate. The
minimum water pressure for the home should be 30psi or
greater. For installation on a private well system with the use of
a pressure tank, the lowest pressure range setting
recommended is 30-50 psi (2.07-3.45 bar). The use of a
pressure reducing/regulating valve before the water heater
(directly after pressure tank on well systems) is an effective
way to maintain constant water pressure to the water heater.
520 PN
Troubleshooting | 27
Watts brand 25AUB- ¾" or N35B -¾" pressure reducing/
regulating valves or equivalent are suggested.
5. If the inlet water temperature is not steady then the hot
water temperature from the water heater will fluctuate. The
520 PN modulates its burners when the flow rate is changed; it
does not have a thermostat and will not adjust to changes in
inlet water temperature.
6. If the inlet water temperature to the water heater is above
70°F, the heater may produce outlet temperatures that are too
hot for most users. A temperature balance shower valve can
automatically mix in cold water to reduce such hot water
temperature. This can slow the flow within the tankless water
heater, decreasing it below activation point, which shuts off the
burners. In the event of any temperature instability with the use
of a temperature balance shower valve, refer to shower valve
manufacturer's instructions for internal adjustment setting. An
adjustment should be made to minimize the amount of cold
water the valve is adding.
7. The gas pressure also needs to be stable and adequate.
Ensure gas pressure is in accordance with manufacturer's
specifications (see chapter 4.9). A gas pressure reading is
needed to proceed further. Contact your original installer or a
local certified gas technician to obtain this reading.
8. A water valve, which has not been serviced, may be
struggling to keep the gas valve open. The water valve requires
periodic maintenance (every 2-5 years depending on water
quality and use) (see chapter 6.2).
7.7
Water is too hot
6. If the water has a high mineral content, the heat exchanger
may be scaled internally. This restricts the water path, causing
the water to boil and produce extremely hot temperatures.
Instructions for descaling the heat exchanger are available at
www.bosch-climate.us.
7.8
Water is not hot enough
1. Verify gas type indicated in rating sticker located on righthand side of cover, coincides with the gas type you are using.
NG is a natural gas unit and LP is for liquid propane.
2. Flow at one particular tap is too great or too many fixtures are
running at one time. Lower flow to stay within heater's
specifications.
3. Ensure the gas control slide button is all the way to the right.
In addition, the temperature adjustment knob on water heater
maybe set too low. Turn the knob clockwise for higher
temperatures and test the water temperature.
4. Shut off installer supplied cold water shut off valve (if none
installed, install before proceeding). Open all hot water taps
supplied by the heater. Wait 5 minutes and check all taps. Any
water running is a sign of a plumbing crossover. Consult a local
plumber or service person for help in correcting a plumbing
crossover.
5. Inspect the water path outside of the heater for
obstructions. Make sure all outlets (i.e. showerheads, faucet
aerators and whole house filters) are clear of debris. Also, the
water heater's inlet filter screen should be inspected and
cleaned (see chapter 6.2).
1. Verify gas type indicated in rating sticker located on righthand side of cover, coincides with the gas type you are using.
NG is a natural gas unit and LP is for liquid propane.
6. The water valve may be dirty, prohibiting it from fully
opening the gas valve. This part needs to be periodically
serviced (every 2-5 years depending on water quality and use)
(see chapter 6.2).
2. Adjust the gas control slide button from three flame position
towards the one flame position for cooler temperatures. If the
water is still too hot, the temperature adjustment knob on the
water heater maybe set too high. Lower the setting and test
water temperature. This dial turns counter clockwise for lower
temperatures and clockwise for higher temperatures.
7. Gas pressure is too low. Ensure gas pressure is in
accordance with manufacturer's specifications (see
chapter 4.9). A gas pressure reading is needed to proceed
further. Contact your original installer or a local certified gas
technician to obtain this reading.
3. Inlet water is preheated. This model does not have a
thermostat and thus will not modulate flame height in order to
prevent over heating. It is designed for a cold water feed only.
Replumb the heater with cold water to the inlet.
7.9
4. Increase the flow rate. Restrictions in the water path can
slow the flow of water through the heater, resulting in very hot
outlet temperatures. Restrictive showerheads and faucet
aerators should be cleaned out or upgraded with less
restrictive ones. In addition, the water heater's inlet filter
should be cleaned and inspected (see chapter 6.2).
5. If water is still too hot, consult service bulletins on
www.bosch-climate.us to lower outlet temperatures further.
520 PN
Burners ignite without hot water flow
1. The water valve may be dirty and sticking, prohibiting it from
fully closing the gas valve. This part needs to be periodically
serviced (every 2-5 years depending on water quality and use)
(see chapter 6.2).
7.10 Low hot water pressure
1. Confirm adequate flow rate through the unit. With cold
supply shut off to the unit, disconnect hot outlet side to the
unit. Place a half gallon jug under hot outlet to catch water.
Open cold supply and measure flow rate out of the unit. With
temperature adjustment knob set all the way clockwise, the
6 720 644 947 (2014/11)
28 | Protecting the environment
flow rate should be close to 2gpm, filling the jug in 15 seconds.
With the temperature adjustment knob set all the way
counterclockwise, the flow rate should be close to 4gpm, filling
the jug in 7 seconds. If the flow rate is not adequate, inspect
and clean the inlet filter screen (see chapter 6.2).
original installer or a licensed gas technician to obtain this
reading.
2. Confirm the incoming water pressure to the unit is above the
required 30psi.
3. For proper combustion at high elevations the inlet gas
pressure should be set at installation to the value shown in
table 3 (while operating at maximum BTU). A gas pressure
reading is needed to proceed further. Contact your original
installer or a licensed gas technician to obtain this reading.
3. Inspect the water path outside of the heater for
obstructions. Make sure all outlets (i.e. showerheads, faucet
aerators and whole house filters) are clear of debris.
4. Ventilation is not adequate. Ensure adequate combustion air
is being supplied to the unit in accordance with manufacturer's
specifications (see chapter 4.6).
4. Be sure to run only one major application at a time with this
unit. Opening too many taps at one time can disperse water
flow resulting in a diminished flow/pressure at all outlets.
5. Make sure the water heater is vented properly. Check for
proper draft and ensure venting is in accordance with
manufacturer's specifications (see chapter 4.7).
5. If the water has a high mineral content, the heat exchanger
may be scaled internally. This restricts the water path, causing
diminished water flow. Instructions for descaling the heat
exchanger are available at www.bosch-climate.us.
6. The water heater has burners much like a furnace. It is
essential that they remain clean and are supplied with
adequate air for combustion. If the flames burn yellow or
orange, it is strongly recommended that the burners be
removed from the unit and cleaned. Once the burners are
removed, the fins in the top of the heat exchanger can be
accessed and brushed or vacuumed clean. Instructions to
remove burners are available at www.bosch-climate.us.
7.11 Noise when heater is running
1. Confirm adequate flow rate through the unit. With cold
supply shut off to the unit, disconnect hot outlet side to the
unit. Place a half gallon jug under hot outlet to catch water.
Open cold supply and measure flow rate out of the unit. With
temperature adjustment knob set all the way clockwise, the
flow rate should be close to 2gpm, filling the jug in 15 seconds.
With the temperature adjustment knob set all the way
counterclockwise, the flow rate should be close to 4gpm, filling
the jug in 7 seconds. If the flow rate is not adequate, inspect
and clean the inlet filter screen (see chapter 6.2).
2. Inspect the water path outside of the heater for
obstructions. Make sure all outlets (i.e. showerheads, faucet
aerators and whole house filters are clear of debris.
Restrictions in the water path can slow water flow through the
heat exchanger causing it to boil and make noise.
3. If the water has a high mineral content, the heat exchanger
may be scaled internally. This restricts the water path, causing
the water to boil resulting in noise and overheating.
Instructions for descaling the heat exchanger are available at
www.bosch-climate.us.
7.12 Burners do not operate cleanly; yellow flames
when operating
1. Verify gas type indicated in rating sticker located on righthand side of cover, coincides with the gas type you are using.
NG is a natural gas unit and LP is for liquid propane.
2. Gas pressure may be inadequate resulting in improper
combustion. Ensure gas pressure is in accordance with
manufacturer's specifications (see chapter 4.6). A gas
pressure reading is needed to proceed further. Contact your
6 720 644 947 (2014/11)
8
Protecting the environment
Packing
The packing box may be fully recycled as confirmed by the
recycling symbol
.
Components
Many parts in the heater can be fully recycled in the end of the
product life. Contact your city authorities for information about
the disposal of recyclable products.
Saving water resources:
▶ Make sure you close all the taps after any use. Avoid leaving
the taps dripping. Repair any leaking tap.
▶ Set the water heat to the temperature you want. This way
you have the precise water flow needed (mixing cold water
to regulate temperature will increase the water flow with
consequent waste of water).
For increased safety shut off the appliance from the main water
supply if your are staying away from home for a considerable
time.
At below freezing temperatures, disconnect the plumbing
connections to the heater and allow the heater to drain.
To prevent any freeze damage, introduce short bursts of
compressed air (20-40 psi) through these connections to
remove the residual water in the horizontal pipes and water
valve.
520 PN
Interior components and diagram parts list | 29
Follow instructions in chapter 5.5 to remove any additional
water remaining in the watervalve and heat exchanger.
9
Interior components and diagram parts list
9.1
Interior components
Fig. 27
[4]
[5]
[10]
[11]
[20]
Functional scheme
Heat exchanger
Burner
Temperature adjustment selector
Water valve
Gas connection
520 PN
[22] Flexible hot outlet
[26] Gas control slide
[30] Pilot gas tubing
[102]Piezo
6 720 644 947 (2014/11)
30 | Interior components and diagram parts list
9.2
Fig. 28
Components diagram
Components Diagram
6 720 644 947 (2014/11)
520 PN
Interior components and diagram parts list | 31
9.3
Parts list
Item Description
Reference
Item Description
Reference
1
8 738 708 496
31
Inlet water connection
8 700 306 110 0
8 738 708 497
32
Selector screw
8 708 500 304 0
Piezo igniter
8 708 108 051 0
2
Front cover
Shield
3
Temp control knob
8 702 000 295 0
33
4
Draft Diverter
8 705 505 442 0
34
Fixing bracket
8 701 302 181 0
5
Exhaust pipe union Ø128
8 705 504 046 0
35
Ignition lead
8 704 401 040 0
8 708 003 192 0
37
Flue gas safety device
8 707 206 445 0
Washer (x10)
8 701 004 043 0
6
Angle bracket
7
Trade mark badge
8 701 103 135 0
38
8
Heat exchanger
8 705 406 386 0
39
Heat exchanger washer
8 700 103 658 0
9
Cold water pipe
8 700 715 061 0
40
Threaded bushing
8 700 306 148 0
8 708 120 618 0
41
Connector
8 700 306 187 0
Water filter
8 700 507 059 0
10
Main burner NG
10
Main burner LP
8 708 120 619 0
42
11
Connector
8 705 209 062 0
43
Outlet Hose
8 700 703 139 0
12
Piezo clip (x10)
8 701 201 019 0
44
Water connection clip
8 701 201 020 0
8 748 107 089 0
45
Plunger
8 703 502 039 0
Volumetric water governor
8 705 705 034 0
13
Sparking plug
14
Pilot gas pipe
8 700 707 369 0
46
15
Tube (x10)
8 740 609 002 0
47
ECO
8 707 206 017 0
16
Pilot screen
8 700 507 067 0
48
Temperature limiter
8 707 206 435 0
8 707 021 396 0
49
Venturi
8 708 205 279 0
Hot water pipe
8 700 715 178 0
17
Gas valve LP
17
Gas valve NG
8 707 021 395 0
50
18
Throttle housing
8 705 502 067 0
51
Gas supply pipe
8 700 715 351 0
19
Washer (x10)
8 701 004 044 0
52
Cover
8 705 500 105 0
20
Pilot injector LP
8 708 200 326 0
Table 13
20
Pilot injector NG
8 708 200 327 0
21
Pilot valve
8 708 500 301 0
22
Poppet valve head (2) NG
8 708 500 358 0
22
Poppet valve head (3) LP
8 708 500 359 0
23
Electromagnet
8 707 201 028 0
24
Electromagnet cap
8 703 305 283 0
25
Valve operation housing
8 708 008 069 0
26
Guide plate
8 701 000 380 0
27
Gas pressure regulator LP
8 707 406 083 0
27
Gas pressure regulator NG
8 707 406 084 0
28
Water valve
8 707 006 344 0
29
Watervalve pushrod (10x)
8 703 204 051 0
30
Diaphragm (L)
8 700 503 084 0
Table 13
520 PN
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32 | LIFETIME LIMITED WARRANTY FOR BOSCH TANKLESS WATER HEATERS
10
LIFETIME LIMITED WARRANTY FOR BOSCH TANKLESS WATER HEATERS
MODELS COVERED
This limited warranty is provided by Bosch Thermotechnology
Corp. (BTC) and covers models 520 PN (hereinafter referred
to as "Water Heater"). This warranty is provided as long as the
Water Heater remains in the possession of the original
purchaser and installed at its original place of installation.
WARRANTY COVERAGE
HEAT EXCHANGER -Limited Warranty
BTC warrants that the heat exchanger will remain free of leaks
for Fifteen (15) years from the date of original installation provided that the heat exchanger is properly maintained by a qualified heating contractor and the other conditions of this
warranty are met. If during this time a leak occurs and BTC
determines that this leak is the result of a defect in workmanship or materials, BTC, will replace the heat exchanger. If the
Water Heater is installed in other than a single family dwelling,
the heat exchanger warranty is limited to two (2) years from
date of original installation.
OTHER WATER HEATER PARTS
If any other part fails within two (2) years after original
installation, BTC will furnish a replacement part fee of charge.
The Water Heater may be delivered with components not
manufactured by BTC ("Other Components). Other
Components are warranted by their manufacturer. BTC also
will warrant the Other Components to be free from defects in
workmanship and material for one year from the date of
installation, provided they are installed and properly
maintained by a qualified heating contractor and the other
conditions of this warranty are met. If a defect exists in the
Other Components, BTC will repair or replace them, if BTC
determines that a defect in workmanship or materials exists.
SERVICE LABOR COSTS
This warranty provides labor costs, at BTC approved rates, for
one (1) year from the date of original installation, provided it is
installed and properly maintained by a qualified heating
contractor and the other conditions of this warranty are met.
ITEMS NOT COVERED
This limited warranty does not cover the following
circumstances:
1. Components or parts not provided by BTC.
2. Serviceable items and normal maintenance as required per
the Installation Manual.
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3. The workmanship of any installer. BTC disclaims and does
not assume any liability of any nature for unsatisfactory
performance caused by improper installation, repair or
maintenance.
4. Any labor or material costs for removal, reinstallation, repair
and replacement of the defective component or part unless
otherwise provided above.
5. Transportation to BTC, if necessary.
6. Damage caused by operation of the Water Heater in a
corrosive atmosphere, scale depots and/or highly mineralized
or unsoftened water supply, electrical failures, flooding, or acts
of God.
7. Any Water Heater that has a failure of malfunction resulting
from operation with either the flame sensor rod or overheat
sensor removed.
8. Damage caused by any attachment or modification to the
Water Heater, including any energy-saving device.
9. Damage caused by operation of the Water Heater at water
temperatures exceeding the maximum rating, or if the water is
not supplied with potable water.
10. Shipping charges, delivery expenses or administrative fees
incurred by the purchaser in repairing or replacing the Water
Heater.
CONDITIONS OF WARRANTY
The warranty herein is void under the following circumstances:
1. Failure or malfunction resulting from improper or negligent
operation, accident, abuse, freezing, misuse, unauthorized
alteration or improper installation, repair or maintenance. See
the Owner's Manual for installation and maintenance
information.
2. Any Water Heater that is operated without a flame sensor rod
or overheat sensor.
3. Any Water Heater that is used or operated in a corrosive
atmosphere or at water temperatures exceeding the maximum
rating, or if the Water Heater is not supplied with potable water.
4. Work performed without prior authorization or approval and
without authorization/requisition number and without proper
documentation verifying compliance with above terms.
LIMITED WARRANTY
OTHER THAN THE OBLIGATIONS OF BTC EXPRESSLY SET
FORTH HERIN, BTC DISCLAIMS ALL WARRANTIES, EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A
PARTICULAR PURPOSE. BTC'S SOLE OBLIGATION WITH
RESPECT TO THE WATER HEATER AND PURCHASER'S
EXCLUSIVE REMEDIES ARE SET FORTH IN THE FOREGOING
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LIFETIME LIMITED WARRANTY FOR BOSCH TANKLESS WATER HEATERS | 33
LIMITED WARRANTY. BTC SHALL NOT BE LIABLE FOR ANY
INDIRECT, PUNITIVE, INCIDENTAL, SPECIAL,
CONSEQUENTIAL OR SIMILAR DAMAGES INCLUDING,
WITHOUT LIMIITATION, INJURY OR DAMAGE TO PERSONS OR
PROPERTY OR DAMAGES FOR LOSS OF USE, LOST PROFITS,
INCONVENIENCE OR LOSS OF TIME.
NOTE THAT ANY REPAIRED OR REPLACED PRODUCT WILL BE
WARRANTED FOR ONLY THE UNEXPIRED TERM OF THE
ORIGINAL WARRANTY.
Some states do not allow the exclusion of limitation of
damages, or limitations on how long an implied warranty lasts,
so the above limitations and exclusions may not apply to you.
WARRANTY CLAIMS PROCESS
If you have a warranty claim you should notify the heating
contractor who installed your water heater and ask that the
contractor notify the distributor from whom the contractor
purchased the Water heater. If this action is not possible or
you don't receive a response, contact Bosch
Thermotechnology Corp., 50 Wentworth Avenue,
Londonderry, NH 03053. To process your claim, you will need
a copy of your original invoice or other proof of purchase and
documentation showing the original installation date and
location. The alleged defective components or parts must be
returned to BTC in accordance with BTC procedure then in
force for handling goods returned for the purpose of inspection
to determine cause of failure (contact BTC if you have
questions regarding the return process). If BTC determines
that the returned components and/or parts are defective and
that this warranty applies, BTC will furnish the repaired or
replacement components and/or parts to an authorized BTC
distributor who, in turn, will forward the components and/or
parts to the heating contractor who installed your Water
Heater.
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34 | Installer Checklist to be completed by installer upon installation
11
Installer Checklist to be completed by
installer upon installation
Serial Number
(8 digit serial number is
located on rating plate on
right side panel)
___ ___ ___ ___ ___ ___ ___ ___
Gas Pressure Reading 1)
Static
Operating
Water Pressure
Building Water Pressure
Range if on Well system
Installing Company
Installer name
Address
Phone
Table 14
1) See Chapter 4.8 and gas pressure table (to be filled out by
installer)
Installation manual should be left with the
owner after the installation is tested and
completed.
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| 35
Notes
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