Bradford White D75T125 User manual

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Manual 47324A
SERVICE
MANUAL
Troubleshooting Guide
and Instructions for Service
(To be performed ONLY by
qualified service providers)
Models Covered
by This Manual:
For The Bradford White
“D” Series Models:
D38T155
D75T(125,160,300)
D65T(370,399)
D80T(180,199,250)
D80T(425,505)
D100T(199,250)
D80L(399,450,505)
D100L(199,250,270,300)
D100S(199,250)
Gas Water Heaters
COMMERCIAL 24 VOLT FLUE DAMPER
SERIES WATER HEATER
®

Table of Contents
Page eF Service Procedure
Introduction 3 - - -
Tool required for service 3 - - -
Sequence of Operation 4 - - -
Troubleshooting 5 - - -
Thermostat Circuit Testing 6 D24-I
Pilot Operation Testing 8 D24-II
Main Burner Operation testing 10 D24-III
Main Burner & Pilot Removal & Inspection 12 D24-IV
Flue Baffle Removal & Inspection 14 D24-V
Anode Removal & Inspection 15 D24-VI
Generic Parts List 16 - - -
Glossary of Terms 19 - - -
Page 2
2

Tools Required for Service
It is intended for this manual to be used by qualified service personal for the primary purpose of
troubleshooting analysis and repair of the Bradford White 24 Volt Flue Damper Series Water
Heater. Understanding the sequence of operation section of this manual will contribute greatly to
troubleshooting this product.
Troubleshooting begins simply by resetting the water heater and observing the lighting sequence
to determine failure mode. This step by step procedure beginning on page 5 will direct the service
provider to a series of test procedures to determine root cause of failure.
Contact Technical support immediately if diagnosis is not determined using the methods described
in this service manual.
Page 3
Manometer: Two types available, a liquid “U” tube type or a digital (magna-helic)
type. This device is used to measure gas and/or air pressures and
vacuum.
Multi-Meter: A digital type is strongly recommended. This device is used to measure
electrical values. The meter you select must have the capability to
measure volts AC, volts DC, Amps, micro-amps and ohms.
Thermometer: Used to measure water temperature. An accurate thermometer is
recommended.
Water Pressure Gage: Used to measure water supply pressure. Also used to determine tank
pressure by adapting to the drain valve of the heater.
Jumper Leads: A length of wire (12" min.) with alligator clip at both ends.
Various Hand Tools: Pipe wrench, channel locks, open end wrench set, 12" crescent wrench,
Allen wrench set, torx bit set, screw drivers (common & phillips), long
reach (12") magnetic tip phillips head screw driver #2 tip, ¼" nut driver,
pliers (common & needle nose), socket set including a 1-1/16 deep well
socket, wire cutters, wire strippers, wire crimpers, torpedo level, small
shop vac, step ladder, and flashlight.
Introduction
3

1Thermostat calls for heat.
The relay closes on the thermostat board, sending 24 volts from the “COM” terminal of the thermostat board
to the flue damper.
2Flue damper begins to rotate open. Once damper is full open, 24 volts is allowed to continue through damper to the
“TH” terminal of ignition module.
3LED on ignition module illuminates.
4
5Once pilot flame is proven, sparking will stop.
Page 4
Sequence of Operation
Trial for ignition (90 second trials, 3 trials with 30 second pause between trials).
Ignition module simultaneously sends:
1. 24 volts from “MV/PV” terminal, to “MV/PV”
terminal of gas valve (common terminal).
2. 24 volts from “PV” terminal, through the
ECO located in the lower thermister, to “PV”
terminal of gas valve to establish
gas flow at pilot.
3. Low current high voltage from “spark”
terminal, to generate spark at the pilot and
ignite pilot gas flow.
4. Pilot flame proving signal (measured in
micro-amps). from the “sense” terminal, to
prove pilot flame.
6Once sparking stops, 24 volts is sent from “MV” terminal on
module, to “MV” terminal on gas valve to establish main
burner gas flow. Main burners ignite from the pilot flame.
The ignition module constantly monitors pilot flame. If pilot
flame is lost, pilot and main burner are shut down. After a
30 second purge period, module will attempt to re-light pilot
beginning at sequence 4 above.
7Main burner fires until the thermostat is satisfied. The relay on
the thermostat board opens, interrupting 24 volts through the
damper and ignition module. Pilot and main burner is turned off.
8Flue damper rotates to the closed position.
WIRING DIAGRAM
LOCKOUT CONDITION
Ignition module will “lockout” if the pilot can not be lit after 3
ignition trials. The ignition module indicates a lockout condition
by the continues flash of the LED located on the module.
Lockout reset is accomplished by interrupting 120 VAC to the
unit for at least 5 seconds.
4

TROUBLESHOOTING
If LED on ignition module is flashing,
reset water heater by turning “OFF”
power. Wait 5 seconds and turn
power back “ON”
Rotate thermostat dial to the
highest setting.
Does damper vane Move to the full
open position?
Does LED light on ignition module
illuminate?
Is there pilot flame?
Does Main burner operate?
Does burner continue until thermostat
set point is reached?
Does flue damper rotate to the closed
position?
System okay.
Y
Y
Y
Y
Y
Y
N
N
N
N
N
N
Remove damper from
heater and
Jump black & yellow wires
ofheater harness
(see photo 2)
Does LED light on
ignition module
illuminate?
Check for debris limiting
damper rotation, if no
debris, replace damper
Y
N
See pilot will not light
(page 8)
See pilot lights, no flame
signal.
(page 9)
See main burner
short cycle
(page 11).
Verify Primary and secondary voltage
at the transformer
(see photo 1)
Ignition Module LED Status
OFF = No power to module
ON = Module has power
Flashing = Module is in lock-out
CAUTION
Use Caution Not to Damage Connectors when making Voltage Measurements or Jumping Terminals
Is there 24 VAC between
terminals “TR” & “TH” of the
ignition module?
(see photo 1A)
Check for debris limiting
damper rotation, if no
debris, replace damper
2
Damper vane show in open position. If damper
is closed, disconnect from harness and
REMOVE damper from water heater.
Harness shown disconnected from damper
with BLACK and YELLOW wires jumped.
See thermostat testing
(page 6).
DANGER
120 volt exposure. Use Caution
To Avoid Personal Injury.
1
Rear terminals
primary
(120 VAC)
Forward terminals
secondary
(24 VAC) Ignition module
Page 5
1A
N
YReplace ignition module
Check damper harness
connection.
Check for 24 VAC
across terminals
“TR” & “TH”
5

SERVICE PROCEDURE D24-I
Thermostat Circuit Testing
CAUTION
Be Careful When Making Voltage
Measurements or Jumping Terminals
Not to Damage or Deform Connectors or
Connector Pins.
DANGER
120 volt exposure. To avoid personal injury,
use caution while performing this procedure.
THERMOSTAT CIRCUIT BY-PASS
Turn power “OFF” to water heater and
locate thermostat board inside control box
of water heater. Disconnect YELLOW wires
from the thermostat board at location
“N.O.” & “COM”. Use a jumper to connect
these two wires together
(see photos 4 & 5).
Does pilot and main burner operate?
3
5
With power on to water heater,
Verify Primary and secondary voltage at
the transformer
(see photo 3)
Turn power on to water heater.
Does LED on ignition module illuminate?
(see photo 6)
This procedure assumes the flue damper is in working order. Be sure damper opens under its own power when the
thermostat circuit is by-passed. Damper must be open or removed during this test. Do not force damper open using your
hands or tools.
Y
N
Y
N
Verify transformer voltage
(see photo 3)
See pilot operation testing
(page 8)
Disconnect ORANGE potentiometer (temp
adjustment dial) wires from thermostat
board (see photo 7)
DANGER
Do not leave thermostat jumper in
place for normal operation.
Turn power “OFF”.
Remove jumper and re-connect wires to
thermostat board. Wires are identified for
proper connection to board.
Check potentiometer for proper resistance values of:
Greater then 4800 Ohms with dial at minimum setting.
Less than 50 Ohms with dial at maximum setting.
(see photo 8).
Are readings correct?
Replace potentiometer
Check Thermisters
(see page 7)
Y
N
7
8
4
Rear terminals
primary
(120 VAC)
Forward terminals
secondary
(24 VAC)
6
LED Location
Page 6
6

°F012345678 9
40 26109 25400 24712 24045 23399 22771 22163 21573 21000 20445
50 19906 19383 18876 18383 17905 17440 16990 16553 16128 15715
60 15314 14925 14548 14180 13823 13477 13140 12812 12494 12185
70 11884 11592 11308 11032 10763 10502 10248 1000 9760 9526
80 9299 9078 8862 8653 8449 8250 8057 7869 7685 7507
90 7333 7165 7000 6839 6683 6531 6383 6238 6098 5961
100 5827 5697 5570 5446 5326 5208 5094 4982 4873 4767
110 4663 4562 4464 4368 4274 4183 4094 4006 3922 3839
120 3758 3679 3602 3527 3453 3382 3312 3244 3177 3112
130 3048 2986 2925 2866 2808 2752 2697 2643 2590 2538
140 2488 2439 2391 2344 2298 2253 2209 2166 2124 2083
150 2043 2004 1966 1928 1891 1856 1820 1786 1753 1720
160 1688 1656 1625 1595 1566 1537 1509 1481 1454 1427
170 1402 1376 1351 1327 1303 1280 1257 1235 1213 1191
180 1170 1150 1129 1110 1090 1071 1053 1035 1017 999
190 982 965 949 933 917 901 886 871 857 842
200 828 814 801 788 775 762 749 737 725 713
In Degrees F
Thermister Resistance at Various Temperatures
Example: If water temperature is 84°F, then the resistance through the sensor would be 8449 (see shaded area).
NOTE: Sensor resistance increases as the temperature falls.
Page 7
SERVICE PROCEDURE D24-I
Thermostat Circuit Testing
Upper thermister location
(applicable models)
Lower thermister
access located inside
control box.
Thermister Resistance Testing
Upper Thermister:
1. Determine resistance value of upper thermister. Test across
grey wires. (see photo 9).
2. Draw quart of water off T&P valve. Using a thermometer,
determine water temperature.
3. Use table below to verify correct resistance per water
temperature measured.
Lower Thermister:
1. Determine resistance value of lower thermister. Test across
blue wires. (see photo 10).
2. Draw quart of water off Drain Valve. Using a thermometer,
determine water temperature.
3. Use table below to verify correct resistance per water
temperature measured.
Are readings
correct?
NReplace
thermister
Y
Check harness
continuity.
Continuity okay?
Y
Replace
thermostat
board
Replace
harness
N
9
10
CAUTION
Be Careful When Making Resistance
Measurements Not to Damage or
Deform Connectors or Connector Pins.
7

SERVICE PROCEDURE D24-II
Pilot Operation Testing
CAUTION
Be Careful When Making Voltage
Measurements or Jumping Terminals
Not to Damage or Deform Connectors or
Connector Pins.
DANGER
120 volt exposure. To avoid personal injury,
use caution while performing this procedure.
Condition:
Pilot will not light,
Ignition module LED is “ON”
Is there 22-27 volts AC output across
terminals “MV/PV” & “PV” of Ignition
Module?Disconnect wires & check
across terminal of module.
(see photo 11)
N
Y
Loosen pilot tubing connection at
the gas valve and soap test.
Is there pilot gas flow out of the
gas valve?
Tighten pilot tube connection at
the gas valve. Check incoming
gas pressure to water heater. if
okay, replace gas valve
Check for clogged or kinked
pilot tube, clogged pilot orifice.
Clean or replace as needed.
(see page 13)
Is there 22-27 volts AC input
across wire leads
“MV/PV” & “PV”
at Gas Valve?
(see photo 12)
Check continuity across ECO
(RED) leads of lower thermister
(see photo 13)
Is continuity okay?
Check wire harness for damage
or loose connections. Repair or
replace as needed.
Reset heater by turning power
“OFF”. Wait 5 seconds and turn
power “ON”. When LED of
ignition module turns “ON” does
ignition module send “spartk”
signal (buzzing or clicking sound)
11
Replace ignition
module
12
Check across
“MV/PV” & “PV”
terminals
Check across “MV/PV”
&“PV” Wire leads to
gas valve
13
Check across RED
wire leads of lower
thermister (ECO).
ECO Specifications
Opens between 181°F/201°F
Closes between 160°F/100°F
N
Y
YY
NN
Y
N
Replace ignition
module
Is there spark at the
pilot?
Check for:
Loose or damaged ignition wire
Grounded pilot electrode
Damaged pilot.
Y
N
Page 8
8

SERVICE PROCEDURE D24-II
Pilot Operation Testing
CAUTION
Be Careful When Making Voltage
Measurements or Jumping Terminals
Not to Damage or Deform Connectors or
Connector Pins.
DANGER
120 volt exposure. To avoid personal injury,
use caution while performing this procedure.
Condition:
Pilot lights, no flame signal.
Module continues to spark until
system “Lock Out”.
Main burner will not light.
Disconnect white flame sense
lead from ignition module at the
“SENSE” location. Set multi-
meter to the “Micro Amps”
setting (ȝA) (see note). Check
micro amp reading. Be sure
module is sparking during this
test.
(see illustration 2)
Micro-amp readings
0.000 Micro Amp = Replace module.
1.0 micro amp or less = Clean pilot flame rod or replace pilot.
Check for loose or damaged
ground wire(s). Are ground wires
okay?
Check for loose or damaged
flame sense lead from pilot to
module. (see illustration 1).
Is flame sense lead okay?
Repair wire lead
or replace pilot.
White flame
sense lead from
pilot
Illustration 1
White wire lead
from pilot
Illustration 2
Meter
Probe
Meter
Probe
Repair ground
wire(s) or replace
as needed.
NOTE:
If multi meter is not capable of
testing micro amps, check
continuity of sense lead. If no
continuity, clean pilot flame rod
or replace pilot.
(see illustration 3)
Illustration 3
Flame rod
Flame rod
Flame rod
Y
Y
N
N
Multi-meter set
to micro-amp
setting (ȝA)
Meter
Probe
Meter
Probe
Multi-meter set
to check
continuity.
Check venting conditions or
negative pressure
Is vent system okay?
Correct improper
venting condition.
N
Is heater condensing causing
pilot interruption?
Determine cause for
condensing and correct.
Under sized heater or high
demand periods
Y
Y
N
Page 9
9

SERVICE PROCEDURE D24-III
Main Burner Operation Testing
CAUTION
Be Careful When Making Voltage
Measurements or Jumping Terminals
Not to Damage or Deform Connectors or
Connector Pins.
DANGER
120 volt exposure. To avoid personal injury,
use caution while performing this procedure.
Condition:
Main burner will not light,
Ignition module LED is “ON”
IsPilot lit? See “pilot will not light”
(page 8).
Does module continue to spark
with pilot lit?
See “Pilot lights, no flame signal”
(Page 9).
Disconnect “brown” wire from
“MV” terminal of ignition module.
Is there 22-27 volts AC across
“MV” terminal of Ignition Module & ground?
(see photo 14)
Disconnect brown wire lead from
“MV” terminal of gas valve.
Is there 22-27 volts AC across
brown wire lead & ground
(see photo 15)
Replace ignition
module
Be sure module LED is “ON”,
pilot is lit and module is not sparking
Recheck voltage across
“MV” terminal of Ignition Module & ground.
Is voltage present?
Check wire harness for damage or
loose connections. Repair or replace
as needed.
Check incoming gas pressure to
gas valve. if okay,
replace gas valve.
14
Disconnect “brown”
wire from “MV”
location of ignition
module.
Ground
Check voltage from
“MV” Terminal of
Ignition module
&ground.
Reconnect brown wire
to ignition module.
N
Y
NN
Y
N
Y
Y
N
Y
Brown wire disconnected
from “MV” terminal of gas
valve
Ground lug of
gas valve
15
Page 10
10