# Transformer trips GFCI

**URL:** <https://boards.straightdope.com/t/transformer-trips-gfci/737518>\
**Category:** Factual Questions\
**Created:** [November 14, 2015, 2:40am UTC](https://boards.straightdope.com/t/transformer-trips-gfci/737518 "2015-11-14T02:40:21Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![Mdcastle](https://avatars.discourse-cdn.com/v4/letter/m/958977/32.png) [@Mdcastle](https://boards.straightdope.com/u/Mdcastle)\
**Post date:** [November 14, 2015, 2:40am UTC](https://boards.straightdope.com/t/transformer-trips-gfci/737518/1 "2015-11-14T02:40:21Z")

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My latest neon sign acquisition, the neon transformer trips the GFCI as soon as it’s energized. I’m assuming this is a short from the primary to the grounded case, and thus I need a new transformer, or is it possible something else is going on? This is an old magnetic unit, (7.5 KV, 30 ma), not a electronic switching supply

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**Author:** ![friedo](https://avatars.discourse-cdn.com/v4/letter/f/8edcca/32.png) [@friedo](https://boards.straightdope.com/u/friedo)\
**Post date:** [November 14, 2015, 3:06am UTC](https://boards.straightdope.com/t/transformer-trips-gfci/737518/2 "2015-11-14T03:06:07Z")

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What happens if you plug it into a non-GFCI outlet?

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**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\
**Post date:** [November 14, 2015, 3:13am UTC](https://boards.straightdope.com/t/transformer-trips-gfci/737518/3 "2015-11-14T03:13:20Z")

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Well, since it’s a transformer, you can just float the case.  
I’d do that, and then use a voltmeter to see if there is any voltage between the case and ground.

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**Author:** ![Mdcastle](https://avatars.discourse-cdn.com/v4/letter/m/958977/32.png) [@Mdcastle](https://boards.straightdope.com/u/Mdcastle)\
**Post date:** [November 14, 2015, 3:23am UTC](https://boards.straightdope.com/t/transformer-trips-gfci/737518/4 "2015-11-14T03:23:47Z")

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It works fine in a non-GFCI outlet. This was originally hardwired into mains, and probably permanently grounded, so no GFCI. I wired a 3-prong cord and plugged it in and it tripped the GFCI immediately. I assume the problem is with the primary because the secondary, HV wiring, and neon tubing are isolated from the main via the transformer. The primary wiring from the terminal strip to the transformer is fine. I tried it lifting the ground (while being extremely careful not to touch the case).

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**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\
**Post date:** [November 14, 2015, 3:33am UTC](https://boards.straightdope.com/t/transformer-trips-gfci/737518/5 "2015-11-14T03:33:30Z")

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It’s just leakage.  
If you must use it on a GFCI, just insulate the case so that it can’t be touched.