Comprehensive Troubleshooting Guide Service Bulletin EP-25

Comprehensive Troubleshooting Guide Service Bulletin EP-25
Service Bulletin EP-25
Models: AE115, AE125, RP17PT, RP27PT (prior to FD108)
Comprehensive Troubleshooting Guide
DANGER: ELECTRIC SHOCK


ELECTRICITY IS EXTREMELY DANGEROUS.
TAKE EXTRA PRECAUTIONS AND
DISCONNECT THIS PRODUCT FROM THE
ELECTRICAL SUPPLY BEFORE CLEANING,
SERVICING OR REMOVING THE COVER.
Step 1 – Document installation details

Complete the “Building and Install” questionnaire.
Step 2 – Water supply and water heater settings

BOSCH ELECTRICAL APPLIANCES
SHOULD ONLY BE SERVICED BY A TRAINED
TECHNICIAN.
Check temperature knob setting:
1.
Make sure the temperature knob is set all the way
clockwise as viewed from the bottom of the water heater.
Tip: The temperature knob setting dictates the output
water temperature: try testing the water temperature at
several settings.
Figure 1
Document results from each troubleshooting step prior
to calling. Without this information documented, we cannot
make a determination as to what is wrong with your water
heater: this will delay a resolution.
Introduction
Who should perform the troubleshooting?
Anyone who has the qualifications to work safely with 240VAC. If you
do not possess the tools or the knowledge to work safely with
240VAC, contact a local professional.
What does this troubleshooting guide cover?
This guide covers every test we can advise you to perform on the
location, installation, and water heater. With ALL the information
from ALL the tests in this guide, it is possible to diagnose any water
heater of this type to a point where we can advise a repair or cover
warranty.
Required tools:
 Adjustable wrench
 Gallon container
 Digital multi-meter
 Phillips head screwdriver
Bottom of Heater
2.

Verify flow rate
1.
For Leaks:
Complete Step 1 only and call Bosch Electric Technical
Support 1-866-330-2729. You will need a description
of the leak, its location and may be asked for digital
pictures.
Document your findings in the Building and Installation
questionnaire.
Using a graduated container (a ½ or 1 gallon container
works well), time how long it takes to fill it with water
from a hot water only faucet or shower. Calculate the flow
rate by taking the size of the container and dividing it by
the time it took then multiplying the answer by 60. This
will yield a gpm result.
2 | EP-25 | AE115, AE125, RP17PT, RP27PT
Example:

Water collected (gallons)
Time to fill (seconds)
2.
1.
X 60 = gallons per minute
Document your findings in the Building and Installation
questionnaire.
If flow rates were below 0.6 gpm on 17kW units and 0.8 gpm on
27kW units, check the inlet water screen:
1.
Shut the water supply off to the water heater and open a
hot water faucet to relieve the pressure.
2.
Remove the cold water supply line from the bottom of the
water heater.
3.
Remove the inlet water screen from the cold water
connection, inspect, and clean it as required.
Keep water supply off to the water heater, isolating the hot
water side of the system.
Do not turn off the water supply to the whole house; only
to the water heater. If you do not have an isolation valve on
the water heater, you cannot perform this test.
Flow rates below 0.6 gpm on 17kW units and 0.8 gpm on
27kW units, will not activate the water heater.
Flow rates above 2.5 gpm on 17kW units may cause
insufficiently warm water.

Checking for plumbing crossovers:
2.
Open ALL hot water taps and set all fixtures to hot only.
3.
Allow some time (approx. 5 minutes) for water to stop
running and pipes to drain. If pipes are drained you should
be able to place hand over end of faucet and feel no
pressure.
4.
If any water continues to flow, you have found a crossover
and one of the following conditions could exist and must
be corrected:
― The most likely cause of this condition is that a mixing
valve has an internal leak allowing cold water to mix with
the hot. While this may not be causing the symptoms
at your water heater, it will certainly affect the ability
of the water heater to reach its maximum stated output
and can cause activation issues and temperature
fluctuations.
Figure 2
― While unlikely, a cold water pipe could be connected to
a hot water pipe. If you have had some plumbing work
done recently and the symptoms coincide with the work
done, you may want to contact the person that did the
work.
Heater bottom
5.
Close all fixtures and reopen water supply to the water
heater.
6.
Document your findings in the Building and Installation
questionnaire.
Step 3 – Visual inspection

Visual Inspection
1.
4.
Install the inlet screen and attach the water line in
accordance with standard plumbing practices. Take care to
not get any pipe sealant inside the unit.
5.
Document your findings in the Building and Installation
questionnaire.
2.

Data subject to change without notice | Printed in the USA | BTC 722002306 C | 10.2013
Thoroughly inspect the water heater’s internal
components. Note the following:
― Burn or scorch marks on the PCB
― Any signs of melted or damaged wires
― Cracks in plastic components
― Alignment of components
― Screw tightness
Document your findings in the Water Heater questionnaire.
Check the flow transducer (Fig. 3):
1.
With the water running at least 1 gpm (gallon/minute),
make sure the flow transducer is turning.
Tip: Use a flashlight to illuminate the flow transducer and
have someone turn the water on and off. Because the flow
transducer spins so fast, it is more likely you will see the
movement as it first begins to spin and as it stops spinning.
2.
Document your findings in the Water Heater questionnaire.
Bosch Thermotechnology Corp.
EP-25 | AE115, AE125, RP17PT, RP27PT | 3 |
Figure 5
Figure 3
27kW terminal block
Supply 1
Supply
S
upply 2
Supply 3
To Supply 1
Flow
Transducer
Sup
To Supply
2
Circuit
Board
To Supply 3
3 independent
40 amp double-pole
circuit breakers
Heater design may vary
3.
Step 4 – Verify the power supply

Figure 6
Check the power supply using an appropriate scale for 240 VAC.
1.
Measure the incoming voltage:
― AE-115 / RP17PT have two readings (Fig. 4)
― AE-125 / RP27PT have three readings (Fig. 5)
2.
Check the pairing of the incoming power connections by
measuring the voltage of all combinations of L1 to L1 and
L2 to L2. Voltage between any of these pairs (L1-L1 or L2L2), indicates an installation error and must be resolved by
an electrician.
Check that voltage is reaching the PCB by measuring the
voltage between the blue and brown power connections
on the board itself (Fig. 6).
Figure 4
17kW terminal block
Supply 1
S
Supply
upply 2
To Supply 1
To Supply
Sup
2
4.
Shut off the circuit breakers powering the appliance, lock
them, and verify that there is no voltage at the unit.
5.
Document your findings in the Water Heater questionnaire.
2 independent
40 amp double-pole
circuit breakers
Data subject to change without notice | Printed in the USA | BTC 722002306 C | 10.2013
Bosch Thermotechnology Corp.
4 | EP-25 | AE115, AE125, RP17PT, RP27PT
Step 5 – Troubleshoot the element assemblies

Verify that circuit breakers are off and there is no voltage at the
unit.

Measure resistance of element assemblies:
7.
Record your results in the Water Heater questionnaire.
Figure 8
COPPER MODULE Top View
Rear of Heater
Black polymer modules only (Fig. 7):
1.
2.
3.
Using a 200 ohm range on a digital multi-meter, test all the
elements on left heating module.
― Outer to Outer (bridge to brown wire)
― Inner to Inner (bridge to gray wire)
― Middle to Middle (red wire to red wire - 27 kW models
only)
Bridge
C
A
B
Using a 200 ohm range on a digital multi-meter, test all the
elements on right heating module.
― Outer to Outer (bridge to white wire)
― Inner to Inner (bridge to black wire)
― Middle to Middle (red wire to blue wire - 27 kW models
only)
Thermal
C
Cutout
Front of Heater
Record your results in the Water Heater questionnaire.
All models:
Figure 7
POLYMER MODULE Top View
Rear of Heater
le
dd
Mi
r
te
Ou
8.
Using the 2000K, 2M, or 20M (Mega ohm) range on a
digital multi-meter, test each element tip to ground.
9.
Record all readings along with where you encountered
them.
10. Using the 200 ohm range on a digital multi-meter, test the
resistances across the terminals of the TCOs (Thermal Cut
Outs). Tip: 17kW units have a single set of terminals to test
and 27kW units have two.
er
Inn
er
Inn
Bridge
le
dd
Mi
ter
Ou
Thermal
C
Cutout
Front of Heater
Copper modules only (Fig. 8):
4.
Using a 200 ohm range on a digital multi-meter, test all the
elements on left heating module.
― Bridge to blue wire
― Bridge to red wire
5.
Using a 200 ohm range on a digital multi-meter, test all the
elements on middle heating module (27 kW models only).
― Bridge to gray wire
― Bridge to brown wire
6.
Using a 200 ohm range on a digital multi-meter, test all the
elements on right heating module.
― Bridge to black wire
― Bridge to white wire
Data subject to change without notice | Printed in the USA | BTC 722002306 C | 10.2013
Bosch Thermotechnology Corp.
EP-25 | AE115, AE125, RP17PT, RP27PT | 5 |
Step 6 – Troubleshoot the control board

Troubleshoot triacs on the control board
1.
Check that the triac screws are snug.
2.
Using a 200 ohm range on a digital multi-meter, test the
triac resistances between the middle and bottom solder
connections.
Tip: 27kW units have six triacs and 17kW units have four.
Figure 9
1
2
3
4
5
6
Incoming
cold water
supply
3.
Record your results in the Water Heater questionnaire.
Data subject to change without notice | Printed in the USA | BTC 722002306 C | 10.2013
Bosch Thermotechnology Corp.
6 | EP-25 | AE115, AE125, RP17PT, RP27PT
Questionnaires
Building and Installation:
STEP 1: Owner’s Name?
Owner’s address?
Owner’s phone number?
Model and serial number?
Model:
Serial Number:
Name of installer and phone number?
Installer:
Phone:
Date of installation?
Date of Installation:____/____/____
Where did you purchase this water heater?
Where in the building is this water heater installed?
Water supply and water pressure?
Municiple
What is the water supply material?
Copper
Plastic
If plastic, does plastic piping connect directly to unit?
Yes
No
When facing water heater, which side of the water heater
does the cold water pipe connect?
Left side
Circuit breaker size and quantity
Single pole
Amperage:________
STEP 2: To what position is the temperature knob set?
Well
Water pressure:_______PSI
Right side
Double pole
Quantity:________
Low
Middle
High
Fixture(s) used for troubleshooting this water heater?
Sink
Shower
Tub
Flow rate of fixture(s) used for troubleshooting?
_______GPM
Inlet filter screen clean?
Yes
No
Plumbing crossover test results - crossover present?
Yes
No
Yes
No
Are there any cracked or melted wires in the unit?
Yes
No
Are there any damaged plastic components in the unit?
Yes
No
Is the flow transducer spinning?
Yes
No
All Fixtures
Water Heater:
STEP 3: Are there any burn or scorch marks on the PCB?
Pair 1 - L1 to L2: ________VAC
STEP 4: Feed voltage:
Pair 2 - L1 to L2: ________VAC
Pair 3 - L1 to L2: ________VAC (27kW only)
Pair 1 - L1 to L1: ________VAC L2 to L2: ________VAC
Feed voltage polarity:
Pair 2 - L1 to L1: ________VAC L2 to L2: ________VAC
Pair 3 - L1 to L1: ________VAC L2 to L2: ________VAC (27kW only)
Voltage to PCB:
Data subject to change without notice | Printed in the USA | BTC 722002306 C | 10.2013
________VAC
Bosch Thermotechnology Corp.
7 | EP-25 | AE115, AE125, RP17PT, RP27PT
Water Heater continued:
STEP 5: Right hand module element resistance
in ohms:
Left hand module element resistance in
ohms:
Right hand module element resistance
in ohms:
Middle module element resistance in
ohms:
Left hand module element resistance in
ohms:
(models with
polymer modules
only)
(models with
polymer modules
only)
(models with
copper modules
only)
Are there any grounded elements? If so, which ones?
Outer to Outer:______Ω
Middle to Middle: ______Ω
Inner to Inner ______Ω
Outer to Outer:______Ω
Middle to Middle: ______Ω
Inner to Inner ______Ω
A to C:______Ω
B to C:______Ω
A to C:______Ω
B to C:______Ω
A to C:______Ω
B to C:______Ω
Yes
No
Thermal Cut Out readings:
Right hand
module
Top terminals________Ω
Bottom terminals________Ω
Thermal Cut Out readings:
Left hand
module
Top terminals________Ω
Bottom terminals________Ω
STEP 6: Are the triac screws all tight?
Triac resistances as appropriate for the unit:
Yes
No
Triac 1______Ω
Triac 2______Ω
Triac 3______Ω
Triac 4______Ω
Triac 5______Ω
Triac 6______Ω
Notes:
After completing this questionnaire, please have your
technician call us while still at the unit at 1-866-330-2729
for diagnosis and resolution. If it is more convenient for
you, please email the completed questionnaire to [email protected]
us.bosch.com and we will reply within one business day.
Bosch Thermotechnology Corp.
50 Wentworth Avenue
Londonderry, NH 03053
Tel: 1-866-330-2729
Fax: 1-603-965-7581
www.bosch-climate.us
Data subject to change without notice | Printed in the USA | BTC 722002306 C | 10.2013
Bosch Thermotechnology Corp.
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