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    Variacs and GFCIs

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    deepee99

    Posts : 1337
    Join date : 2012-05-23
    Location : Wallace, Idaho

    Variacs and GFCIs

    Post by deepee99 on Tue Oct 04, 2016 1:02 pm

    A lot of people on this forum swear by Variacs. A simple and likely dumb question. Would the Variac plug into the GFCI, or would you put the GFCI(s) on the output side?

    corndog71

    Posts : 454
    Join date : 2013-03-19
    Location : It can get windy here

    Re: Variacs and GFCIs

    Post by corndog71 on Tue Oct 04, 2016 3:16 pm

    deepee99 wrote:A lot of people on this forum swear by Variacs. A simple and likely dumb question. Would the Variac plug into the GFCI, or would you put the GFCI(s) on the output side?

    Well, think about it this way: Whatever you plug into the GFCI will be protected by the GFCI. If you want to also protect your variac then plug your variac into the GFCI.

    deepee99

    Posts : 1337
    Join date : 2012-05-23
    Location : Wallace, Idaho

    Re: Variacs and GFCIs

    Post by deepee99 on Tue Oct 04, 2016 3:27 pm

    corndog71 wrote:
    deepee99 wrote:A lot of people on this forum swear by Variacs. A simple and likely dumb question. Would the Variac plug into the GFCI, or would you put the GFCI(s) on the output side?

    Well, think about it this way:  Whatever you plug into the GFCI will be protected by the GFCI.  If you want to also protect your variac then plug your variac into the GFCI.
    Thanks. The reason I asked was I had a variac that developed a ground fault all on its own...

    Peter W.

    Posts : 152
    Join date : 2016-08-07
    Location : Melrose Park, PA

    Re: Variacs and GFCIs

    Post by Peter W. on Tue Oct 04, 2016 4:09 pm

    deepee99 wrote:
    corndog71 wrote:
    deepee99 wrote:A lot of people on this forum swear by Variacs. A simple and likely dumb question. Would the Variac plug into the GFCI, or would you put the GFCI(s) on the output side?

    Well, think about it this way:  Whatever you plug into the GFCI will be protected by the GFCI.  If you want to also protect your variac then plug your variac into the GFCI.
    Thanks. The reason I asked was I had a variac that developed a ground fault all on its own...

    Variacs are Variable Autotransformers - meaning that they are NOT isolation transformers - there is only one (1) winding, with a variable take-off to control voltage. Those who expect them to behave as a standard transformer could be unhappily surprised. And, if tested as a standard dual-or-more-winding transformer, they will display faults right down the line.

    http://www.electronics-tutorials.ws/transformer/trans33.gif?x98918 Variac Schematic.

    Multi-winding multi-tap transformer: http://www.learnabout-electronics.org/ac_theory/images/Power-txfmr-shematic.gif Note that there is no connection between the primary and the secondary.

    NOTE: Unless you have a metered variac - volts and amps - it is, really, not very useful, and in fact can be genuinely dangerous.

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