® U TTW 75 Series Gas Water Heaters SERVICE MANUAL Troubleshooting Guide and Instructions for Service (To be performed ONLY by qualified service providers) Models Covered by This Manual: U2TW75T*RN UTW475S76R*N (*) Denotes Warranty Years Manual 238-50629-00A Save this manual for future reference
Bradford White U2TW Series Gas Water Heaters Table of Contents Page Page 2 2 U2TW Service Procedure Introduction 4 --- How to Use This Manual 5 --- Tool Required for Service 5 --- Specifications 6 --- Control Timings 8 --- Sequence of Operation 9 --- Troubleshooting 12 --- Burner and Inner Door/Gasket Removal, Inspection Replacement and Reinstallation 14 I Burner Operation Inspection, Cleaning and Replacement 17 II Pilot Testing, Cleaning and Replacement 19 III Pressure Sw
WARNING: If the information in these instructions is not followed exactly, a fire or explosion may result causing property damage, personal injury, or death. FOR YOUR SAFETY Do not store or use gasoline or other flammable, combustible, or corrosive vapors and liquids in the vicinity of this or any other appliance. WHAT TO DO IF YOU SMELL GAS Do not try to light any appliance. x Do not touch any electrical switch; do not use any phone in your building.
Introduction The new Bradford White U2TW & UTW4 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. In addition, the U2TW & UTW4 water heaters provide Ultra Low NOx emissions.
How to Use This Manual It is intended for this manual to be used by qualified service personnel for the primary purpose of troubleshooting and repair of the Bradford White U2TW Series water heaters. Understanding the sequence of operation section of this manual will contribute greatly to troubleshooting the water heater. The Honeywell WV4462A Electronic Gas Control will display error codes in the event of abnormal operation.
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. Gas Pressure 6.0" W.C. min. and 14.0" W.C. max. Venting System Power vent through the wall or vertical through the roof Approved Vent Materials PVC, CPVC or ABS Minimum Clearance for Servicing 18" from top, 24" from front, 4" sides and rear. Water Supply Pressure 150 PSI maximum allowable working pressure.
Specifications Vent Tables Venting Specifications: 3" Diameter (7.6 cm) PVC Vent Connector Lengths Terminating # of Elbows Maximum Length ft (m) Minimum Length ft (m) Through the Wall Through the Wall Through the Wall Through the Wall 1 2 3 4 45 (13.7) 40 (12.2) 35 (10.7) 30 (9.1) 2 (.6) 2 (.6) 2 (.6) 2 (.6) Through the Roof Through the Roof Through the Roof Through the Roof 0 1 2 3 50 (15.2) 45 (13.7) 40 (12.2) 35 (10.7) 7 (2.1) 7 (2.1) 7 (2.1) 7 (2.1) 4" Diameter (10.
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.
Sequence of Operation Power up Sequence 1 Start Up. Upon power up, the control runs a safe-start check with a typical start-up delay of 1-5 seconds. 2 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. If the device is within range the control resumes normal operation with no perceivable delay.
Sequence of Operation Normal Heating Sequence (cont.) 7 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. Pressure switch / Blower temperature switch- If either switch opens, pilot valve and main valve is shut down.
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.
Troubleshooting Green LED Indicator Observe green LED indicator on 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. LED Status Control Status Service Procedure None, control LED not on or flashing No electrical power Control power switch in “OFF” position. Supply voltage interrupted.
Troubleshooting LED Status Control Status Probable Cause 1. Unstable pilot. 2. Pilot tube blocked or restricted. 3. Oxidation build up on pilot electrode. 4. Wire damage to pilot assembly or bad connection at gas valve. Six-one flash, three second pause Failed to light pilot. System auto resets. Six-two flash, three second pause 1. Vent blockage or improper vent configuration. Pressure switch or 2. Pressure switch tubing kinked or blocked. blower temp switch 3. Faulty pressure switch.
R U TTW SERVICE PROCEDURE I Burner and Inner Door/Gasket Removal, Inspection, Replacement and Reinstallation Gas Control shown in the “OFF” position Inner Door Removal Procedure Step 1. Position gas control power switch to the “OFF” position and unplug heater from wall outlet. Step 2. Remove outer jacket burner access door. Step 3. Remove wire clip from main burner feedline. Step 4. Inner Door Removal.
R U TTW SERVICE PROCEDURE I Burner and Inner Door/Gasket Removal, Inspection, Replacement and Reinstallation Inner Door Gasket Replacement Procedure WARNING If the information in these instructions is not followed exactly, a fire or explosion may result causing property damage, personal injury or death. Step 6. After inspection of inner door as noted in step 5, completely remove gasket and adhesive residue from burner door and right side inner door as needed. Step 7.
R U TTW SERVICE PROCEDURE I Burner and Inner Door/Gasket Removal, Inspection, Replacement and Reinstallation 6 Position Thermopile Wire, Pilot Tube and Igniter Wire Step 10. Position thermopile wires, pilot tube and igniter wire against burner door flange gasket (see photo 6). Step 11. Firmly place right side inner door flange against the burner door flange and secure with two ¼” drive screws from step 4d (see photo 7). DO NOT OVER TIGHTEN SCREWS. Step 12.
R U TTW SERVICE PROCEDURE II Burner Operation Inspection, Cleaning and Replacement Main Burner Inspection, Cleaning and Replacement At periodic intervals (not more than 6 months) a visual inspection should be made of the main burner for proper operation and to insure no debris is accumulating. Main burner should light smoothly from pilot and burn with a blue flame with a minimum of yellow tips.
R U TTW SERVICE PROCEDURE II Burner Operation Inspection, Cleaning and Replacement Burner Cleaning (Continued) Step 4. Thoroughly inspect burner screen and burner venturis and remove any loose debris accumulation. Inspect burner screen for any openings larger than the normal screen openings. Step 5. Use compressed air and/or a vacuum to remove any scale or other debris accumulation from the burner screen and venturis. Burner Screen Burner Venturis Manifold Brackets Step 6.
R U TTW SERVICE PROCEDURE III Pilot testing, Cleaning and Replacement Gas Control shown in the “OFF” position Pilot Assembly Inspection, Testing and Replacement Step 1. Position gas control power switch to the “OFF” position and unplug water heater from wall outlet. Step 2. Remove outer jacket door. Step 3. Remove burner and right side of inner door per SERVICE PROCEDURE I, steps 3 and 4. Step 4. Remove burner assembly from combustion chamber. Step 5.
R U TTW SERVICE PROCEDURE IV Pressure Switch Testing and Replacement Pressure Switch Testing WARNING 115 volt potential exposure. Use caution making voltage checks to avoid personal injury. Step 1. Position gas control power switch to the “OFF” position. Step 2. Remove the three screws (Phillips screw driver) from control access cover on blower assembly and remove cover (see photos 1 and 2). Step 3. Carefully remove pressure switch from blower housing (see photo 3).
R U TTW SERVICE PROCEDURE IV Pressure Switch Testing and Replacement Pressure Switch Replacement WARNING 115 volt potential exposure. Use caution to avoid personal injury. Step 1. Position gas control power switch to the “OFF” position. Step 2. Remove the three screws (Phillips screw driver) from control access cover on blower assembly and remove cover (see photos 4 and 5). 5 4 Control Access Cover Screws Pressure Switch 6 Step 3.
R U TTW SERVICE PROCEDURE V Blower Testing and Replacement WARNING 115 volt potential exposure. Use caution when making voltage checks to avoid personal injury. Blower Testing Step 1. Position gas control power switch to “ON” position and adjust control to call for heat. 9 10 Step 2. Remove the three screws (Phillips Screw driver) from control access cover on blower assembly and remove cover (see photos 9 and 10).
R U TTW SERVICE PROCEDURE V Blower Testing and Replacement Gas Control shown in the “OFF” position Blower Removal Step 1. Position gas control power switch to the “OFF” position and unplug heater from wall outlet. Step 2. Disconnect vent system from exhaust adapter on top of blower. Step 3. Remove exhaust adapter from blower (blade screw driver) and retain for use on new blower. Step 4. Unplug cord sets from blower. Step 5. Remove the three blower mounting screws (¼" nut driver). Step 6.
R U TTW SERVICE PROCEDURE VI Blower Temperature Switch Testing and Replacement WARNING 115 volt potential exposure. Use caution to avoid personal injury. Blower Temperature Switch Testing. Step 1. Position gas control power switch to the “OFF” position. Step 2. Remove the three screws (Phillips screw driver) from control access cover on blower and remove cover (see photos 17 and 18). Step 3. Locate blower temperature switch (see photo 19).
R U TTW SERVICE PROCEDURE VI Blower Temperature Switch Testing and Replacement Blower Temperature Switch Replacement. WARNING 115 volt potential exposure. Use caution to avoid personal injury. Step 1. Position gas control power switch to the “OFF” position and unplug water heater from wall outlet. Step 2. Remove the three screws (Phillips screw driver) from the control access cover on blower and remove cover (see photo 20 and 21).
R U TTW SERVICE PROCEDURE VII Gas Control Testing and Replacement Gas Control Replacement Step 1. Rotate knob of the gas control to the “OFF” position. Step 2. Turn off gas supply to water heater. Step 3. Disconnect gas supply line from gas control. Step 4. Turn off water supply and drain water heater completely. Step 5. Remove the wire clip from the feedline. Gas Control shown in the “OFF” position Step 6.
R U TTW SERVICE PROCEDURE VII Gas Control Testing and Replacement Manifold Pressure Testing (this procedure presumes a maximum line pressure of 14.0" w.c.) Gas Control shown in the “OFF” position Step 1. Position gas control power switch to the “OFF” position. Step 2. Remove pressure tap plug (3/16" hex wrench) and install 1/8" NPT pipe, coupling, & pressure tap. Step 3. Connect manometer to pressure tap. Step 4.
R U TTW SERVICE PROCEDURE VIII 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. Resistance must be within 25,000 ohms and 45,000 ohms. If outside of this range replace the simulated resistive device.
R U TTW SERVICE PROCEDURE IX Resettable Thermal Switch Testing and Replacement Resettable Thermal Switch Continuity Testing Step 1. Remove outer jacket door. Step 2. Disconnect red wire leads from resettable thermal switch. Red Wire Leads Step 3. Using a multimeter capable of measuring continuity (Ohms), place one probe of meter on one of the brass connection tabs of the resettable thermal switch, and the remaining probe on the other connection tab. Step 4.
R U TTW SERVICE PROCEDURE IX Resettable Thermal Switch Testing and Replacement Resettable Thermal Switch Replacement Step 1. Position gas control power switch to the “OFF” position. Step 2. Remove outer jacket door. Step 3. Disconnect red wire leads from resettable thermal switch. Gas Control shown in the “OFF” Position ¼” Hex Drive Manifold Cover Screws Step 4. Remove (2) ¼” hex drive screws from the manifold cover and slid to the right to remove from burner assembly. Step 6.
R U TTW SERVICE PROCEDURE X Safety Circuit Voltage Trace WARNING 115 volt potential exposure. Use caution making voltage checks to avoid personal injury. Safety Circuit Voltage Trace NOTE: This procedure assumes a cool tank. 24 Step 1. Remove three screws (Phillips Screw driver) from control access cover on blower and remove cover (see photo 24 and 25).
R U TTW SERVICE PROCEDURE XI 115 VAC Trace WARNING 115 volt potential exposure. Use caution making voltage checks to avoid personal injury. 115 VAC Circuit Trace Step 1. Verify 115VAC 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 None, Control LED not on or flashing. LED status Short flash, once every four seconds. LED status “Heartbeat”, alternates bright/dim. LED status Various flashing error codes.
R U TTW SERVICE PROCEDURE XII 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. Gas Control shown in the “OFF” Position Step 1. Position gas control power switch to the “OFF” position and unplug water heater from wall outlet. Step 2. Turn off cold water supply to water heater.
R U TTW SERVICE PROCEDURE XIII 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. Gas Control shown in the “OFF” Position Step 1. Position gas control power switch to the “OFF” position and unplug water heater from wall outlet. Step 2. Turn off cold water supply to water heater.
R U TTW SERVICE PROCEDURE XIV Flue Baffle Inspection and replacement Remove blower to gain access to flue baffle Disconnect vent system from exhaust adapter. Step 1. Position gas control power switch to the “OFF” position and unplug water heater from wall outlet. Step 2. Disconnect vent system from exhaust adapter on top of blower. Step 3. Unplug cord sets from blower. (see photo 33). Step 4. Remove the three blower mounting screws (¼" nut driver) (see photo 33). Step 5.
Glossary of Terms BTU GPM Hz KWh LED NPT Ohms PSI RPM ECO VAC W.C.
NOTES Page 3 37
NOTES Page 38 38
Parts List 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. Flue Baffle Inlet Dip Tube Inner Door Gasket Kit Hot Water Outlet Anode Heat Trap Inlet Heat Trap Outlet Blower Assembly T&P Valve Outer Door Gas Control Gas Control Wire Harness Brass Drain Valve 13. Ultra Low NOx Burner 14. Right Side Inner Door Assembly 15. Pilot Assembly 16. ¼” Manifold Mount Hex Head Screw 17. Manifold Mount 18. Main Burner Orifice 19. Main Burner Feedline 20. Resettable Thermal Switch 21. Manifold Cover 22.
