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TTW 75 SERIES
®
Gas Water Heaters
SERVICE
MANUAL
Troubleshooting Guide
and Instructions for Service
(To be performed ONLY by
qualified service providers)
For Bradford White
TTW
Series Models:
®
M2TW75T*(BN,CX)
TW475S76(B,C)* (N,X)
(*) Denotes Warranty Years
Manual 47150A
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Summary of Contents for Bradford White TTW 75 SERIES
- Page 1 TTW 75 SERIES ® Gas Water Heaters SERVICE MANUAL Troubleshooting Guide and Instructions for Service (To be performed ONLY by qualified service providers) For Bradford White Series Models: ® M2TW75T*(BN,CX) TW475S76(B,C)* (N,X) (*) Denotes Warranty Years Manual 47150A Save this manual for future reference...
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Page 2: Table Of Contents
Bradford White TTW Series Gas Water Heaters Table of Contents Page TTW Service Procedure Introduction - - - How to use this manual - - - Tool required for service - - - Specifications - - - Control Timings - - -... - Page 3 CAUTION WARNING: If the information in these Incorrect operation of this instructions is not followed exactly, a fire or appliance may create a hazard to explosion may result causing property damage, life and property and will nullify the personal injury, or death. warranty.
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Page 4: Introduction
Introduction The new Bradford White TTW2 & TW4 water heaters are designed to provide reliable performance with enhanced standard features. New design features include reliable spark to pilot ignition system, enhanced diagnostics, simplified servicing, significantly quiet operation and additional vent lengths. -
Page 5: How To Use This Manual
In some difficult to diagnose conditions, it may be necessary to isolate the heater from the vent system to determine the problem. Contact the Bradford White technical support group immediately if diagnosis can not be made using the methods described in this service manual. -
Page 6: Specifications
Specifications Power supply Dedicated 115VAC, 60 Hz, 15A Gas Supply Pipe Minimum 1/2" NPT (schedule 40 black iron pipe recommended) Approved Gas Type Natural or Propane. Unit must match gas type supplied. Gas Pressure 5.0" W.C. min. for Nat gas, 11.0" W.C. min. for L.P. gas, 14.0" W.C. maximum (Nat. & L.P.) Venting System Power vent through the wall or vertical through the roof Approved Vent Materials... - Page 7 Specifications Vent Tables Venting Specifications: 3" Diameter (7.6 cm) PVC Vent Connector Lengths # of Maximum Minimum Terminating Elbows Length ft (m) Length ft (m) Through the Wall 45 (13.7) 2 (.6) Through the Wall 40 (12.2) 2 (.6) Through the Wall 35 (10.7) 2 (.6) Through the Wall...
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Page 8: Control Timings
Specifications Control Timings Ignition State Timing Pre-purge 2 Seconds Trial for Ignition 90 Seconds Flame Stabilization Period 3 Seconds Inter-purge 15 Seconds Flame Failure Response Time 1.5 Seconds (2 second. Maximum; 1 second minimum.) Post-purge 15 Seconds PS Fault Delay (failed open/close) Retry after 2 Minutes Soft Lockout Retry after 5 Minutes... -
Page 9: Sequence Of Operation
Sequence of Operation Power up Sequence Start Up. Upon power up, the control runs a safe-start check with a typical start-up delay of 1-5 seconds. Simulated Resistive Load Device Check. To assure no outputs are energized if the “Simulated Resistive device” is out of range, the control will test the the device for proper operating range. - Page 10 Sequence of Operation Normal Heating Sequence (cont.) Steady state operation. During Steady State Operation the Control Monitors: Thermostat temperature sensor- When set point temperature is satisfied, gas valve is shut down and blower will post purge for 15 seconds. Control LED flashes a short flash once every 4 seconds (idle) status code.
- Page 11 Sequence of Operation Abnormal Operation (cont.) 3. Pressure Switch/Blower Temperature Fault: a) Pressure switch closed at start of call for heat - The gas control waits four seconds then, proceeds to flash 2 times with 3 second pause. The control waits 2 minutes and then turns on blower for 30 seconds. The blower turns off after 30 seconds and the control waits for pressure switch to open.
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Page 12: Troubleshooting
Troubleshooting Green LED Observe green LED indicator on Indicator Electronic gas control. Error flash codes are displayed with a three second pause before repeating. Check and repair the system as noted in the troubleshooting table below. Control Service LED Status Probable Cause Status Procedure... - Page 13 Troubleshooting Control Service LED Status Probable Cause Status Procedure 1. Unstable pilot. Failed to light 1. Page 14 2. Pilot tube blocked or restricted. Six-one flash, three pilot. 3. Oxidation build up on pilot electrode. second pause System auto 2-4. Page 16 4.
- Page 14 TTW SERVICE PROCEDURE I Burner Operation Inspection, Adjustment, Cleaning and Replacement Burner Inspection and Air Shutter Adjustment. At periodic intervals (every 6 months) a visual inspection should be made of the pilot and main burner for proper operation and to assure no debris is accumulating. Pilot flame should be stable, some causes for an unstable pilot flame are: a) Water heater vent is less than the allowable vent length.
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Page 15: Burner Cleaning
TTW SERVICE PROCEDURE I Burner Operation Inspection, Adjustment, Cleaning and Replacement Burner Cleaning Step 1. Position gas control power switch to the “OFF” position and unplug heater from wall outlet. Remove Outer Step 2. Turn off gas supply to water heater. door. -
Page 16: Pilot Testing, Cleaning And Replacement
TTW SERVICE PROCEDURE II Pilot testing, Cleaning and Replacement Pilot Inspection, Testing and Replacement Step 1. Position gas control power switch to the “OFF” position and unplug heater from wall outlet. Remove Outer door. Step 2. Turn off gas supply to water heater. Remove Step 3. - Page 17 TTW SERVICE PROCEDURE III Pressure Switch Testing and Replacement Pressure Switch Testing WARNING 120 volt potential exposure. Use caution Step 1. Position power switch on gas control making voltage checks to avoid personal injury. to the “OFF” position. Step 2. Remove the three screws (Phillips screw driver) from control access cover on blower assembly and remove cover (see photo 1).
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Page 18: Pressure Switch Testing And Replacement
TTW SERVICE PROCEDURE III Pressure Switch Testing and Replacement Pressure Switch Replacement WARNING 120 volt potential exposure. Use caution to avoid personal injury. Step 1. Position gas control power switch to “OFF” position. Step 2. Remove the three screws (Phillips screw driver) from control access cover on blower assembly and remove cover (see photo 3). - Page 19 TTW SERVICE PROCEDURE IV Blower Testing and Replacement WARNING Blower Testing 115 volt potential exposure. Use caution when making voltage checks to avoid personal injury. Step 1. Position gas control power switch to “ON” position and adjust control to call for heat. Step 2.
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Page 20: Blower Testing And Replacement
TTW SERVICE PROCEDURE IV Blower Testing and Replacement Blower removal Step 1. Position gas control power switch to the “OFF” position. Step 2. Unplug blower power cord from wall outlet. Remove exhaust adapter and retain for use on new blower. Step 3. -
Page 21: Blower Temperature Switch Testing And Replacement
TTW SERVICE PROCEDURE V Blower Temperature Switch Testing and Replacement Blower Temperature Switch WARNING Testing. 120 volt potential exposure. Use caution to avoid personal injury. Step 1. Position power switch on gas control to the “OFF” position. Step 2. Remove the three screws (Phillips screw driver) from control access cover on blower and remove cover (see photo 14). - Page 22 TTW SERVICE PROCEDURE V Blower Temperature Switch Testing and Replacement Blower Temperature Switch WARNING Replacement. 120 volt potential exposure. Use caution to avoid personal injury. Step 1. Position gas control power switch to the “OFF” position and unplug heater from wall outlet. Step 2.
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Page 23: Thermal Well Testing
TTW SERVICE PROCEDURE VI Gas Control/Thermal Well Testing and Replacement Gas Control Testing See pages 24 & 25 for gas control input & output testing. Thermal Well Testing Position gas valve power Disconnect thermal switch to the “OFF” well wire harness position and disconnect thermal well harness from gas control. -
Page 24: Gas Control & Thermal Well Testing & Replacement
TTW SERVICE PROCEDURE VI Gas Control/Thermal Well Testing and Replacement WARNING Stored water may be HOT when performing the following steps in this procedure. Take necessary precaution to prevent personal injury. Determine Water Temperature Inside Tank Note: It is important to understand once the resistance for the thermal well is determined from page 23, water flow through the heater should not occur. - Page 25 TTW SERVICE PROCEDURE VI Gas Control & Thermal Well Testing and Replacement Gas Control & Thermal Well Removal From Water Heater Gas Control Step 1. Position gas valve power switch to the “OFF” Thermal position and Unplug Heater from power supply. Well Step 2.
- Page 26 TTW SERVICE PROCEDURE VI Gas Control & Thermal Well Testing and Replacement Gas Control Assembly to Thermal Well Step 1. Install threaded end of thermal well into tank. Be sure thermal well flange is positioned as shown in photo 24 for proper control alignment.
- Page 27 TTW SERVICE PROCEDURE VII Simulated Resistive Device Testing Simulated Resistive Device Testing Step 1. Position power switch on gas control to the “OFF” position. Step 2. Disconnect simulated resistive device from gas control. Step 3. Using a multi-meter set to the ohms setting check resistance of simulated resistive device.
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Page 28: Safety Circuit Voltage Trace
TTW SERVICE PROCEDURE VIII Safety Circuit Voltage Trace Safety Circuit Voltage WARNING Trace 120 volt potential exposure. Use caution making voltage checks to avoid personal injury. NOTE: This procedure assumes a cool tank. Step 2. Remove three screws (Phillips Screw driver) from control access cover on blower and remove cover (see photo 26). -
Page 29: 115Vac Circuit Trace
TTW SERVICE PROCEDURE IX 120 VAC Trace WARNING 120 VAC Circuit Trace 120 volt potential exposure. Use caution making voltage checks to avoid personal injury. Step 1. Verify 120VAC and proper polarity at wall outlet. Step 2. With unit plugged in and control power switch in the “ON” position verify LED status. LED status LED status LED status... -
Page 30: Dip Tube Inspection And Replacement
TTW SERVICE PROCEDURE X Dip Tube Inspection and replacement Dip Tube Inspection and Replacement WARNING Water Heater components and stored water may be HOT when performing the following steps in this procedure. Take necessary precaution to prevent personal injury. Step 1. Position on/off switch of gas control valve to “OFF”... -
Page 31: Anode Inspection And Replacement
TTW SERVICE PROCEDURE XI Anode Inspection and replacement Anode Inspection and Replacement WARNING Water Heater components and stored water may be HOT when performing the following steps in this procedure. Take necessary precaution to prevent personal injury. Step 1. Position on/off switch of gas control valve to the “OFF” position and unplug water heater from wall outlet. -
Page 32: Flue Baffle Inspection And Replacement
TTW SERVICE PROCEDURE XII Flue Baffle Inspection and replacement Disconnect vent Remove blower to gain access to system from exhaust adapter. flue baffle Step 1. Position gas control power switch to the “OFF” position Blower Mounting and unplug blower from wall outlet. Screws Step 2. -
Page 33: Glossary Of Terms
Glossary of Terms British Thermal Units Gallons per Minute Hertz KW/h Kilowatts per hour Light Emitting Diode National Pipe Thread Ohms Ohms of resistance Pounds per Square Inch Revolutions per Minute Temperature Cut Off Volts Alternating Current W.C. Inches of Water Column °C Degrees Centigrade °F... - Page 34 NOTES Page 34...
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Page 35: Parts List
Parts List Optional 1. Blower Complete 13. Heat Trap Inlet 25. Cast Iron Burner 37. Gas Control 38. Gas Control Service 2. Air Mixing Inlet cover 14. Inlet Dip Tube 26. Pilot Assy. (L.P.) 3. Pressure Switch 15. Wire Harness 27. - Page 36 Email parts@bradfordwhite.com techserv@bradfordwhite.com www.bradfordwhite.com...