Bradford-White U2TW50T'FRN User Manual

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Control access cover
Locate the blower temperature switch.

Blower Temperature Switch Testing

Blower Installation (cont’d)

Step 11. Secure blower in place using mounting screws from step 7. Step 12. Reinstall exhaust adapter from step 4.

Step 13. Reinstall dilution air clip from step 5.

Step 14. Reconnect vent system to exhaust adapter. Step 15. Reconnect cords from step 6.

Step 16. Position gas control power switch to the “ON” position. Step 17. Verify proper blower operation.

Blower Temperature Switch Testing

WARNING

115 volt potential exposure. Use caution making voltage checks to avoid personal injury.

Step 1. Move the gas control power switch to the “OFF” position.

Gas control power switch

Step 2. Remove the three screws (Phillips screw driver) from control access cover on blower and remove cover.

Blower temperature

switch location

Step 3.

Air mixing inlet

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Blower Temperature Switch Testing

Blower Temperature Switch Testing (cont’d)

Switch Setting

Opens on rise @ approximately 165oF

Auto resets on fall @ approximately 160oF

Cool switch to below 160oF

Disconnect wire leads to

 

 

 

 

 

switch. Using multi-meterset

N

Replace switch

 

to the ohms setting. Is there

 

 

 

 

 

(see page 33).

 

continuity between the switch

 

 

 

 

 

 

 

 

terminals?

 

 

 

 

 

 

Y

 

 

 

 

 

 

 

 

 

 

N

 

 

Reconnect wire leads and ob-

Y

 

 

 

 

serve heater operation. Do

 

Do switch

Y

Exhaust

 

 

exhaust gas temperatures

 

 

contacts

 

temperature

rise to or above 170oF with

 

 

open?

 

is too hot.

vent connected?

 

 

 

 

 

 

N

 

 

 

 

 

 

Do switch con-

Y

Replace switch

 

 

 

 

 

tacts open?

 

 

(see page 33).

 

 

N

Switch OK

Page 32

Common causes for high exhaust temperature

1.Vent length is below minimum allowable

2.Vent diameter not to specification

3.Restricted dilution air inlet

4.Missing or deteriorated flue baffle

5.Gas pressure is out of specification

32

Snip retaining lug from blower housing
Control access cover

Blower Temperature Switch Replacement

Blower Temperature Switch Replacement

WARNING

115 volt potential exposure. Use caution making voltage checks to avoid personal injury.

Step 1. Move the gas control power switch to the “OFF” position.

Gas control power switch

Step 2. Remove the three screws (Phillips screw driver) from the control access cover on the blower assembly and remove cover.

Step 3. Locate blower temperature switch.

Step 4. Disconnect red and yellow wire leads from the switch.

Step 5. With an appropriate tool such as side cutters, snip the retaining lug from the

blower housing to allow removal of temperature switch.

Blower temperature switch location

Step 6. Remove switch from blower housing.

Step 7. Install new switch. Be sure switch is properly seated in mounting area.

Step 8. Reconnect red and yellow wires to new switch. Wires are interchangeable with either terminal.

Step 9. Position the gas control power switch to the “ON” position and verify proper heater operation.

Step 10. Replace control access cover from step 2.

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Thermal Well Testing

Thermal Well Testing

CAUTION

Do not use standard multi-meterprobes for this testing. Doing so will damage the connector. Use special pin type electronic probes or small diameter wire pins inserted into connector.

Follow the procedure, below, if the water heater gas control has gone into a ECO lockout (4 flash, 3 second pause). Reset the gas control by rotating the setpoint knob to the minimum setting for at least 6 seconds before returning to the desired water temperature setting.

Step 1. Unplug the thermal well connector from the gas

control.

Thermal well connector

Step 2. With a multi-meterset to the ohms setting, measure the resistance between the middle and right side wires.

Step 3. With a multi-meterset to the ohms setting, measure the resistance between the middle and left side wires.

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Determine Tank Temperature

Thermal Well Testing (cont’d)

Determine the correct resistance values using the Determine the Water Temperature Inside the Tank procedure on page 23. If the values are correct, replace the gas control, otherwise replace the thermal well.

Determine Water Temperature Inside Tank

WARNING

Stored water may be HOT when performing the following steps in this procedure. Take necessary precaution to prevent personal injury.

Note: It is important to understand once the resistance for the thermal well is determined using the Thermal Well Testing Procedure on page 21, water flow through the water heater should not occur. Prior to performing the steps below, turn off the cold water supply to the water heater. This will prevent cold water flow into the tank affecting the resistance value of thermal well.

Step 1. Move the gas control power switch to the “OFF”

position.

Gas control power switch

Step 2. Draw approximately 4 gallons of water from the drain valve into a container and discard. Draw an additional gallon and immediately measure the water temperature using an accurate thermometer. It may be necessary to open a hot water faucet to allow heater to drain.

Step 3. Using the chart on page 23, determine the correct resistance value for the water temperature from Step 2.

Example: If temperature of water is 84°F, then the resistance through the sensor would be 8449 (see shaded area). NOTE: Sensor resistance increases as the temperature falls.

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Component Disassembly

Sensor Resistance at Various Temperatures

In Degrees F

°F

0

1

2

3

4

5

6

7

8

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

10000

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

Gas Control & Thermal Well Removal From Water Heater

Step 1. Move the gas control power switch to the “OFF” position.

Gas control power switch

Step 2. Unplug the water heater from the wall outlet.

TTW (water heater) power cord

Step 3. Drain the water heater to a point below the gas control level.

Step 4. Turn off the gas supply to the water heater and disconnect the gas piping from the gas control.

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Flats of thermal well

Gas Control Removal

Gas Control & Thermal Well Removal From Water Heater (cont’d)

Step 4. Disconnect the pilot tube using a 7/16” wrench and the main burner feedline with a 3/4” wrench from the gas control.

Pilot and main feedlines

Step 5. Disconnect the wire harnesses and spark igniter/ flame sense wire from the gas control.

Gas control

Spark igniter/flame sensor wire

Step 6. Remove the gas control & thermal well by rotating the flats of the Thermal Well counter clockwise using a 1- wrench.

Gas Control Removal From Thermal Well

Following the steps below allows for the removal of the gas control from the thermal well without removing the thermal well from the tank.

Step 1. Move the gas control power switch to the “OFF”

position.

Gas control power switch

Step 2. Unplug the water heater from the wall outlet.

TTW (water heater) power cord

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Gas Control Assembly

Gas Control Removal From Thermal Well (cont’d)

Step 3. Turn off the gas supply to the water heater and disconnect the gas piping from the gas control.

Step 4. Disconnect the pilot tube using a 7/16” wrench and the main burner feedline with a 3/4” wrench from the gas control.

Pilot and main feedlines

Step 5. Disconnect the wire harnesses and spark igniter/

flame sense wire from the gas control.

Gas control

Spark igniter/flame sensor wire

Step 6. Using the gas control service tool, p/n 239-45991-00, available from your BWC parts supplier, insert the tool into the back of the gas control.

Gas control service tool

Step 7. Pivot the tool towards the water heater, as far as possible. Lift straight up on the gas control. The gas control should move about 1/8". Hold the gas control in position and remove the tool. Lift straight up on the gas control to remove it completely from the thermal well.

Gas Control Assembly to the Thermal Well

Step 1. Install the threaded end of the thermal well into the tank. Be sure the thermal well flange is positioned properly to allow for proper gas control installation. Tighten the thermal well using a 1-5/16”wrench.

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Gas Control Assembly

Gas Control Assembly to the Thermal Well (cont’d)

Step 2. Route the wire leads back into relief opening.

Wire leads on thermal well

Slots in thermal well

Relief opening

Step 3. Align the slots located on the thermal well flange with the tabs located on the back of the gas control.

Tabs on back of gas control

Step 4. Carefully push the gas control back onto the thermal well flange as far as possible towards the water heater. Then, slide the gas control down to lock into position.

Step 5. Install the burner assembly and connect the pilot and main feedlines to the gas control using a 7/16” and 3/4” wrench, respectively.

Pilot and main feedlines

Step 6. Reconnect the wire harnesses to the gas control.

Wire harnesses

Step 7. Reconnect the gas piping to the gas control. Restore the gas supply and check for gas leaks.

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Flammable vapor sensor harness

Flammable Vapor Sensor Testing

Gas Control Assembly to the Thermal Well (cont’d)

Step 8. To resume operation, follow the instructions located on the water heater lighting instruction label. Or, use the lighting instructions located in the water heater installation and operating manual.

Flammable Vapor Sensor Testing

CAUTION

Do not use standard multi-meterprobes for this testing. Doing so will damage the connector. Use special pin type electronic probes or small diameter wire pins inserted into connector.

Step 1. Move the gas control power switch to the “OFF” position.

 

 

Gas control power

 

 

switch

Step 2.

Disconnect the flammable vapor sensor harness

from the gas control.

Flammable vapor

 

 

sensor harness

Step 3. Using a multi-meterset to the ohms setting, measure the resistance of the flammable vapor sensor and resettable thermal switch. The resistance must be between 3,000 and 48,000 ohms. If the resistance is out of this range, verify

settable thermal switch has not been tripped. If it hasn’t, the thermal switch.

115 VAC Circuit Trace

Step 1. Verify 115VAC and proper polarity are at the wall outlet.

Step 2. With the water heater plugged in and the gas control power switch in the “ON” position verify LED status.

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