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  1. #1
    Join Date
    Jul 2009
    Columbia, MD

    how many millivolts?

    customer wanted me to check his fireplace. the thermopile was putting out in between 420-480 MV. i jumped out the gas valve and it wouldnt fire.

    i put in a new thermopile and let it warm up. had a reading of 375 MV. the box saids its a 750 MV thermopile. i jumped the gas valve and it fired right up.

    how many MV is normal to be generated from these things. made sure pilot was clear and burning good.

  2. #2
    Join Date
    Mar 2001
    Ilwaco, Washington
    Take two MV readings. One with a load and one without. If you have the proper tool, a gas valve dropout test will tell you what the valve requires to operate.
    One way to outthink people is to make them think you think. They'll think you're not really thinking what you're trying to get them to think you think...........

  3. #3
    Join Date
    Mar 2010
    Kent, WA.
    from documentation i have from robertshaw on millivolt gas valves you should have a minimum of 325mv from the thermopile with nothing connected to it. basically hold the pilot knob and test it out of the circuit. if this is good then you should have 200mv with the thermopile hooked up to the gas valve and the main burner on. if the main gas valve does not ignite or you have less than the dropout mv when trying to fire, the valve coil might be bad or there is resistance somewhere in the circuit not allowing the generated voltage to open the valve. the valves i have used has a cut out around 100 to 120 mv.
    Cheap work is not good, good work is not cheap...

    A positive attidude will not solve all your problems, but it will annoy enough people to make it worthwhile.

  4. #4
    Join Date
    Aug 2011
    A new 750 should put out 750 if pilot flame is proper. Under load 550 is good. Alot of valves require min. 350mv to open burner.
    There is no bad beer, some just taste better than others.

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