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Thread: Electrical curiosities, take 2

  1. #21
    Join Date
    Nov 2010
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    Quote Originally Posted by Snapperhead View Post
    Im thinking I see grounded transformers in Commercial units more often than Resi
    Probably but all of them have to have one side of the secondary grounded or you'll read 12v to ground. You just don't see the jumper in the resi units so much, I think the transformers themselves use the case to bond to the metal they're mounted to in the unit. Every now and then I come across a unit that reads 12v to ground on common and hot. I don't know if trans got replaced with one with no bond or what, I'll have to pay attention more next time.

  2. #22
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    Nov 2010
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    I don't know how I read the OP wrong instead of coil I thought he said transformer. I was wondering what everyone was talking about. I had one a couple summers ago where a mouse got one of my two wires I did the old one side of the contactor to ground for a week or two until I could go back and pull a new wire. Guess you found a unit where he didn't feel like coming back.

    Using ground isn't a good way to do it, the current that contactor is pulling still has to make it back to the transformer it just does it through house ground back to the bond to the trans at the furnace. I think anyway I might have to isolate a trans and see if ground and one side of a low volt trans will pull in a contactor, I don't think it will.

  3. #23
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    Nov 2011
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    Quote Originally Posted by Poodle Head Mikey View Post
    Is what you saw Right? No; of course not.

    Is it legal? No; of course not.

    Will it work? Almost certainly.

    Did the common wire have continuity end-to-end?

    How difficult would it be to run a new wire from this coil you saw and the transformer location? <g>
    Over the the years with heat pumps, I've seen a bunch of "open commons" on the stat cable...and I never understood why the common conductors fail but oftentimes there is an unused conductor available to switch for the faulty conductor. Sometimes there isn't...

    I had one situation where the XFMR common wasn't grounded, the common conductor to the condenser was open, there were no spares available and running new cable was not an option. I grounded the XFMR common and connected the condenser common to ground...

    Sure, it ain't kosher but it's 24V...I wouldn't do similar with an open neutral and use ground for a 120V circuit.

  4. #24
    Join Date
    Jul 2007
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    Beautiful, Philadelphia, the City of Brotherly Love!
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    If the common wire of a transformer is not grounded either wire could be used as the common, that is why Lennox has been grounding their transformers since 1970.
    “You don't get paid for the hour. You get paid for the value you bring to the hour.” Jim Rohn

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