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Thread: Power vent tank blower constantly running

  1. #1
    DIY Junior Member rexles's Avatar
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    Default Power vent tank blower constantly running

    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??

  2. #2
    In the trades Dana's Avatar
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    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.

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    DIY Junior Member rexles's Avatar
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    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.

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    General Engineering Contractor ballvalve's Avatar
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    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.
    Last edited by ballvalve; 12-30-2011 at 10:34 AM.

  5. #5
    DIY Junior Member rexles's Avatar
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    Quote Originally Posted by ballvalve View Post
    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.

  6. #6
    Master Plumber master plumber mark's Avatar
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    Cool 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...

  7. #7
    DIY Junior Member rexles's Avatar
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    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.
    Quote Originally Posted by master plumber mark View Post
    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...

  8. #8
    General Engineering Contractor ballvalve's Avatar
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    all the rigs I see shut off the blower if the vacuum switch does not pull in.

  9. #9
    Master Plumber master plumber mark's Avatar
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    Quote Originally Posted by rexles View Post
    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.


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