Power vent tank blower constantly running

Rexles · Dec 29, 2011

I have a Bradford White MI TW 50 gl power vent tank.
Blower was making noise and had come apart. Replaced blower assy with factory parts.
Plugged in and ran fine. After tank was hot, blower would not shut off. Blower runs even though the burner is not on. 2" PVC vent pipe is not hot to the touch.
Any Ideas??

Dana · Dec 29, 2011

Assuming (in lieu of evidence) that you wired it correctly, that would imply that the relay the powers the blower is stuck on (contacts welded, spring broken, something) or something even further back the control chain is fried.

In the meantime just letting it run is not a good option, since it's sucking heat out of the tank 24/7, blowing it out the vent.

Sponsor · 2022-01-29T12:20:58-0800

Rexles · Dec 29, 2011

Wiring was simple plug that could only be plugged in one way.
It seems the diaphram switch was not being pulled in when blower was running. I removed the blower and remounted it using silicone to seal around the base where it sets on the HW tank. One of the sheet metal screw holes was stripped out so I installed bigger screws. Plugged it in and it fired right up.
Evidently the lack of a good seal was enough to make the vacuum on the diaphram switch not pull in. The blower is controlled by the thermostat, and the gas valve is controlled by the vacuum switch on the blower unit.

Ballvalve · Dec 30, 2011

Those air switches are very sensitive, when the diaphragm gets harder with age, the required vacuum climbs, and it still works when you 'suck on it'.

Odd, however, because if the diaphragm switch does not close, you shouldnt get gas to the valve, and the blower should power down.

Sequence-call for heat- blower starts- air switch senses vacuum from blower- igniter on- blower on. gas valve opens.

Rexles · Dec 30, 2011

ballvalve said:
Those air switches are very sensitive, when the diaphragm gets harder with age, the required vacuum climbs, and it still works when you 'suck on it'.

Odd, however, because if the diaphragm switch does not close, you shouldnt get gas to the valve, and the blower should power down.

Sequence-call for heat- blower starts- air switch senses vacuum from blower- igniter on- blower on. gas valve opens.

You are correct on your sequence, however the blower is controlled by the thermostat and does not shut off until satisfied. The vacuum switch pulls in the gas valve and even if the gas valve does not open the blower continues to run. Tech at BW told me that over the phone and it was also proven true by standing there and watching it.

Master Plumber Mark · Dec 30, 2011

shut it down

you would be wise to check the air switch, thermostat, relay
that tells the unit to shut off...
and whatever else they tell you could be the trouble...

the blower will run till it burns out, and it will certainly
cool down the heater and make it come on and re-heat...
costing you money....

shut it down, take it apart again and start over...

Rexles · Dec 31, 2011

Evidently you failed to read my post correctly. It was fixed when I pulled off the blower assy and sealed it with silicone and screwed it down again with abigger screw that had stripped out. It is running the way it should.

master plumber mark said:
you would be wise to check the air switch, thermostat, relay
that tells the unit to shut off...
and whatever else they tell you could be the trouble...

the blower will run till it burns out, and it will certainly
cool down the heater and make it come on and re-heat...
costing you money....

shut it down, take it apart again and start over...

Ballvalve · Jan 2, 2012

all the rigs I see shut off the blower if the vacuum switch does not pull in.

Master Plumber Mark · Jan 3, 2012

rexles said:
Evidently you failed to read my post correctly. It was fixed when I pulled off the blower assy and sealed it with silicone and screwed it down again with abigger screw that had stripped out. It is running the way it should.

Evidently you failed to read my post correctly.

I am so very sorry sherlock...... how silly of me old chap.....

evidently , these other two guys did not read your
post very well either.....

please stick your snooty nose up in the air for them too,

whould you please.

Power vent tank blower constantly running

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