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TTW SERVICE PROCEDURE  V

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 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 16)

16

Step 3.

Locate blower temperature switch (see photo 17)

Step 4.

Disconnect red and yellow wire leads from 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 (see photo 18).

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 yellows wires to new switch. Wires are 
interchangeable with either terminal.

Step 9.

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

Step 10.

Replace control access cover from step 2.

Blower temperature 

switch location

17

Snip retaining lug 

from blower housing

18

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Summary of Contents for tw450s

Page 1: ...e performed ONLY by qualified service providers Models Covered by This Manual M1TW40S F BN CX SX M1TW50S F BN CX SX M1TW60T F BN CX SX M4TW40T F BN SX M4TW50T F BN SX M4TW60T F BN SX M2TW50T F BN CX S...

Page 2: ...IV Blower Temperature Switch Testing and Replacement 22 V Gas Control Thermal well Testing Replacement 24 VI Flammable Vapor Sensor Testing and Replacement 28 VII Safety Circuit Voltage Trace 29 VIII...

Page 3: ...OT ATTEMPT TO LIGHT ANY GAS APPLIANCE IF YOU ARE NOT CERTAIN OF THE FOLLOWING Liquefied petroleum gases propane gas and natural gas have an odorant added by the gas supplier that aids in the detection...

Page 4: ...ote error free wiring Increased Vent Lengths increased venting performance is achieved while maintaining Energy Factor FHSR performance The TTW1 M1TW TTW2 M2TW TW4 water heaters use a combustion syste...

Page 5: ...s and or air pressure 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 v...

Page 6: ...um decrease 80 TTW2 M2TW TW4 Models Normally open closes on vacuum increase 1 28 opens on vacuum decrease 1 25 Power supply Dedicated 115VAC 60 Hz 15A Approved Gas Type Natural or Propane Unit must ma...

Page 7: ...um Straight Length ft m 3 Diameter 7 6 cm PVC Vent Connector Lengths 1 115 35 0 10 3 1 Through the Wall 2 110 33 5 10 3 1 Through the Wall 3 105 32 0 10 3 1 Through the Wall 4 100 30 5 10 3 1 Through...

Page 8: ...ft m Minimum Straight Length ft m 4 Diameter 10 2 cm PVC Vent Connector Lengths 1 10 3 1 Through the Wall 2 10 3 1 Through the Wall 3 10 3 1 Through the Wall 4 10 3 1 Through the Roof 0 60 18 3 7 2 1...

Page 9: ...out Indefinite See Page 24 to reset Simulated Resistive Load Lockout Indefinite cycle power to reset Hardware Error Lockout Indefinite self clears if fault clears for at least 15 seconds Verify Resist...

Page 10: ...with no perceptible delay If the Flammable Vapor Sensor is out of range the control LED immediately flashes 7 times with 3 second pause 1 2 Blower energizes 5 Trial for pilot ignition 90 seconds a The...

Page 11: ...stive delay for 2 minutes and flashes 7 times then once with a three second pause This process is repeated 5 times until the control either returns to normal operation or proceeds to flammable vapor l...

Page 12: ...ntrol turns off the blower and flashes 6 times then 2 times with 3 second pause The gas control waits 5 minutes before repeating ignition sequence 4 Trial For Ignition Fault a Pressure switch opens du...

Page 13: ...trode 4 Wire damage to pilot assembly or bad connection at gas valve 1 Page 15 2 4 Page 17 1 Pressure switch tubing kinked or blocked 2 Blocked pressure tap on switch or blower 3 Faulty pressure switc...

Page 14: ...ge 22 1 Vent blockage or improper vent configuration 2 Pressure switch tubing kinked or blocked 3 Faulty pressure switch 4 Vent termination being affected by wind 5 Blower not spinning up to speed 6 B...

Page 15: ...ld be stable some causes for an unstable pilot flame are a Water heater vent is less than the allowable vent length b Gas pressure is out of specification c Pilot flame not fully engulfing spark flame...

Page 16: ...ain burner orifice from feedline wrench on steel burners 3 8 wrench on cast iron inspect orifice clean or replace if necessary Step 11 Reassemble burner and reinstall into water heater Restore gas sup...

Page 17: ...pilot hood If so carefully adjust electrode to a gap distance of 3 32 09 from pilot hood Step 11 Visually inspect igniter flame sense electrode for oxidation build up Carefully clean any oxidation usi...

Page 18: ...s there blockage Replace switch see page 19 Position gas valve power switch to the ON position and adjust thermostat to call for heat this will start the blower Check with multi meter do pressure swit...

Page 19: ...er from step 2 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 P...

Page 20: ...f 2 15 to 2 30 W C Step 1 Position gas control power switch to ON position and adjust control to call for heat Step 2 Remove the three screws Phillips Screw driver from control access cover on blower...

Page 21: ...n any debris from jacket head of water heater Step 9 Set new blower with gasket in place using locating pins on blower flange to line up with location holes in jacket head Be sure not to damage gasket...

Page 22: ...s Phillips screw driver from control access cover on blower and remove cover see photo 14 Step 3 Locate blower temperature switch see photo 15 Reconnect wire leads and observe heater operation Do exha...

Page 23: ...4 Disconnect red and yellow wire leads from 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 see photo...

Page 24: ...Control Thermal Well Testing and Replacement Page 24 Gas Control Testing See pages 29 30 for gas control voltage testing Once the thermal well resistance values are known the water temperature must al...

Page 25: ...ance at Various Temperatures 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 WARN...

Page 26: ...rom gas control Step 3 Disconnect wire harnesses burner assembly from gas control Step 4 Using gas control service tool 239 45991 00 available from your BWC parts supplier Insert tool into back of gas...

Page 27: ...Control Thermal Well Testing and Replacement Page 27 24 25 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 alig...

Page 28: ...stance of flammable vapor sensor see caution below Resistance must be within 3 000 ohms and 48 000 ohms If outside of this range replace flammable vapor sensor Flammable Vapor Device Testing Flammable...

Page 29: ...hear or can you see the igniter sparking Y Y Is LED on gas valve flashing the heartbeat code alternating bright dim N Safety circuit voltage is OK No voltage from gas control call for technical suppor...

Page 30: ...r set to volts AC is there 115VAC across terminals shown in photo 29 N Y 28 29 Reconnect cord set shown in photo 28 Repair damage Check for damage to AC supply power cord Y N Replace Blower 32 Check f...

Page 31: ...let nipple dip tube Inlet nipple dip tube should be free of cracks and any blockage Hydro jet slots should be open and free of any blockage Any damage such as cracks restriction due to deformation or...

Page 32: ...Step 5 Visually inspect outlet nipple anode Outlet nipple anode should show signs of depletion this is normal If depletion is of the original anode diameter approximately diameter replacement is reco...

Page 33: ...p 8 Reinstall baffle into flue tube Be sure baffle hanger tab are inserted into notch location at the top of the flue tube see photos 35 36 Step 9 Check Burner to insure no scale has accumulated durin...

Page 34: ...effected by any of the above gasket replacement is not required If replacement is required proceed to Inner Door Gasket Replacement Procedure Inner Door Gasket Replacement Procedure WARNING If the in...

Page 35: ...TTW SERVICE PROCEDURE XIII Inner Door Gasket Removal Inspection Replacement and Reinstallation Page 35 Step 7 Clean any residual gasket residue or other debris from combustion chamber surface before...

Page 36: ...ing 1 4 hex drive screws from step 3a DO NOT OVER TIGHTEN SCREWS Verify both left and right sides of the inner door are properly positioned and sealed against the combustion chamber Step 12 Replace ou...

Page 37: ...shop vacuum to remove any scale or other debris accumulation Using a soft brush clear jacket openings from any dirt dust restrictions or other obstructions Step 6 Remove any debris from burner assembl...

Page 38: ...KW h Killo watts per hour LED Light Emitting Diode NPT National Pipe Thread Ohms Ohms of resistance PSI Pounds per Square Inch RPM Revolutions per Minute TCO Temperature Cut Off VAC Volts Alternating...

Page 39: ...n Burner Orifice 21 Pilot Assy Nat 22 Pilot Orifice 23 Feedline 24 Burner Assy L P 25 Cast Iron Burner 26 Pilot Assy L P 27 Pilot Orifice L P 28 Feedline 29 Jam Nut 30 Air Shutter 31 Main Burner Orifi...

Page 40: ...Email parts bradfordwhite com techserv bradfordwhite com www bradfordwhite com...

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