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  1. #1
    Join Date
    Aug 2004
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    I am working on the new generation boxes that Envirotech has come out with in the past couple of years. I am burning up the red heat board on the three board stack. I have found a note in my lit. that says no more than a 10VA holding coil is permitable.
    My basic theory in electrical formulas has not been used to its fullest in the past years. So....

    1. I want to put a fuse in line to prevent board BARB-QUE, I think 10VA is .416 amps, but am not sure. Please tell me how to firgure out.

    2. The standard off the shelf contactor is "x" amount of dollars, if you call Carrier and have them order one to match the FPB it is four times higher. How do I determine the VA on the contactor?

    Control voltage is 24VAC/ the off the shelf contactor has 10 ohms across the coil.

    The contactor could be my problem, because of past building engineers changing parts on the box. I know the contactors are not original. No high voltage crosses control voltage at all.


  2. #2
    Join Date
    Aug 2000
    Austell, Ga.
    Post Likes
    You are correct on the .416 Amps being 10va.
    The DC-Resistance you measured on the coil can "Never" be used to deternine the AC Resistance(Impeadance). It serves only to determine whether or not the coil is open or not.
    On any and all these new boards using either Triac outputs or the micro-miniture relay outputs, it is "Always" best to install a pilot relay to accept the signal from whatever board you have, and then using it's contacts to break the larger contactors coil circuit...
    5 or 6 bucks invested there or a couple of bucks more for one with a indicator light showing power on the coil, will surely save one much grief dow
    Ain't "None" of us as smart as "All" of us..

  3. #3
    Join Date
    Feb 2004
    Post Likes
    I agree with richard I would use a RIB in this case it should solve your problem.

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