Bradford-White Corp D38T155 User Manual

COMMERCIAL 24 VOLT FLUE DAMPER

SERIES WATER HEATER

Gas Water Heaters

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)

Manual 47324A

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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

1

Thermostat 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.

2

Flue 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.

3

LED on ignition module illuminates.

4

5

Once 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.

6

Once 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.

7

Main 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.

8

Flue 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 h eater by turning “OFF”

power. Wa it 5 seconds and turn

p

ower back “ON”

R

otate thermostat dial to the

h

ighest setting.

Does damper vane Move to the full

o

pen position?

Does LED light on ignition module

illuminate?

Is there pilot flame?

Does Main burner o perate?

Does burne r continue until th ermostat

set point is reached?

Does flue damper rotate to the closed

position?

System oka y.

Y

Y

Y

Y

Y

Y

N

N

N

N

N

N

Remove damper from

h

eater and

J

ump black & yellow wires

o

f heater harness

(see photo 2)

D

oes LED light on
i

gnition mod ule

i

lluminate?

C

heck for debris limiting

d

amper rotation, if no

d

ebris, 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 vo ltage

at the transfor mer

(

see pho to 1)

I

gnition Module LED Status

O

FF = No power to module

O

N = Module has power

F

lashing = Module is in lock-out

C

AUTION

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 pho to 1A)

Check for debris limiting

damper rotation, if no

debris, replace damper

2

Damper van e show in op en position. If damper

is closed, disconnect from harness and

REMOVE damper from water hea ter.

Harness shown disconnected from damper

with BLACK and YELLOW wires jumped.

S

ee thermostat testing

(

page 6).

DANGER

120 volt exposure. Use Caution

To Avoid Personal Injury.

1

Rear ter minals

primary

(120 VAC)

Forward terminals

secondary

(24 VAC)

Ignition module

Page 5

1A

N

Y

Replace ignition module

Check damper harness

connection.

Check for 24 VAC

across ter minals

“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.

T

HERMOSTAT CIRCUIT BY-PASS

T

urn 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 w ires together

(see photos 4 & 5).

Does pilot and main bu rner operate?

3

5

W

ith power on to water heater,

Verify Primary and secondary voltage at

the transformer

(see pho to 3)

Turn power on to water heater.

Does LED on ignition module illuminate?

(see photo 6)

T

his 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 tran sformer vo ltage

(see photo 3)

See pilot operation testing

(page 8)

Disconne ct 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 identifie d for

proper connection to b oard.

Check potentiometer for proper resistance values of:

Greater then 4800 Ohms with dial at minimum setting.

Less than 50 Oh ms with dial at maximum setting.

(see photo 8).

Are readings correct?

Replace potentiometer

Check Thermisters

(see page 7)

Y

N

7

8

4

Rear term inals

primary

(120 VAC)

Forward terminals

secondary

(24 VAC)

6

LED Location

Page 6

6