mrrjm
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Re: Do It Yourself: 240v from two 120v sources

Mon Jul 21, 2014 6:37 pm

I built this circuit. Using a Nema 6-50 outlet. It works perfectly unless I plug it into GFCI outlets. They trip as soon as the charging adaptor is plugged in. Is there a way around this?

I plan on taking a trip in a week. Most all hotel outdoor outlets are GFCI so I need it to work with GFCI outlets. Is that possible?

Thanks in advance.


Ray

Alex
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Location: Tucson, AZ

Re: Do It Yourself: 240v from two 120v sources

Mon Jul 21, 2014 8:38 pm

mrrjm wrote:I built this circuit. Using a Nema 6-50 outlet. It works perfectly unless I plug it into GFCI outlets. They trip as soon as the charging adaptor is plugged in. Is there a way around this?

I plan on taking a trip in a week. Most all hotel outdoor outlets are GFCI so I need it to work with GFCI outlets. Is that possible?
GFCI outlets sense the difference in current between the Hot and Neutral legs, assuming that if there is a difference, then the excess current is going to ground. This protects someone even when there is no ground connected to their device or outlet. Unfortunately, you can't do a anything about this since the 240 is generated by drawing current from the 2 hot sides and no current is flowing through the neutral and thus causing an imbalance between the hot and neutral which causes the GFCI to trip.
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nsayer
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Re: Do It Yourself: 240v from two 120v sources

Mon Jul 21, 2014 8:41 pm

Alex is right. The whole concept is fundamentally incompatible with GFI protected outlets. There's no workaround other than using a different outlet.

fooljoe
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Re: Do It Yourself: 240v from two 120v sources

Mon Jul 21, 2014 11:30 pm

It's possible to combine two 120v outlets that are GFCI'd (or on the same leg for that matter), but not using anything like the simple adapter most have made. Basically you need an isolation transformer (go back to page 24 of this thread.) Another option would be to use a second charger.
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nsayer
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Joined: Tue Aug 20, 2013 6:26 pm

Re: Do It Yourself: 240v from two 120v sources

Tue Jul 22, 2014 6:11 am

An isolation transformer that would handle an EVSE's 30 amps - or even 15 - would be a monster.

mrrjm
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Re: Do It Yourself: 240v from two 120v sources

Tue Jul 22, 2014 6:24 am

What I might do if I had to charge and there was not other option is try to bypass the GFCI. Of course if the panel breaker is GFCI then that won't work

fooljoe
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Re: Do It Yourself: 240v from two 120v sources

Tue Jul 22, 2014 10:21 am

nsayer wrote:An isolation transformer that would handle an EVSE's 30 amps - or even 15 - would be a monster.
Did you look at the discussion on page 24? We're talking about 12 amps (maybe up to 16) from two 120v outlets, and apparently you only need a transformer sized for the power from one outlet. ~2 kva should do. Still not something I'd like to carry around in my trunk all the time, but definitely not too big to carry if there was a definite need.
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johnrhansen
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Re: Do It Yourself: 240v from two 120v sources

Tue Jul 22, 2014 10:31 am

actually there might be a way. use a small transformer to make a circulating current through both neutrals exactly equal to the current through the line. It could be done. It would be a high current, but just enough voltage to drive the current through the neutral wires and the bus bar of the panel.
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nsayer
Posts: 75
Joined: Tue Aug 20, 2013 6:26 pm

Re: Do It Yourself: 240v from two 120v sources

Tue Jul 22, 2014 10:38 am

I don't think that will work. You're still pulling current from the hot line that you're not returning to the neutral. That will always trip a GFI.

fooljoe
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Re: Do It Yourself: 240v from two 120v sources

Tue Jul 22, 2014 10:46 am

mrrjm wrote:What I might do if I had to charge and there was not other option is try to bypass the GFCI. Of course if the panel breaker is GFCI then that won't work
What sort of hotel are you going to? I can't imagine most hotels would sanction you removing the faceplates from their outdoor outlets to defeat their safety protections. Also, what makes you think there will be multiple outdoor outlets within reach on different circuits? I'd think it fairly likely that many or all of the outdoor outlets would be on the same circuit anyway, in which case you're not going to be upping the power you can draw no matter what you can do.

Anyway, if you're driving a Leaf the battery's so small you're probably fine just charging on 120v anyway, so why go to all this trouble? And have you ruled out finding any public charging stations nearby on plugshare if you absolutely need to charge faster? Most hotels have shuttles available that can drop you off and pick you up from somewhere nearby with a charging station.
RavCharge.com | 2012 Rav4-EV | 2011 Leaf SL w/QC batt replaced 11/20/15 | Clipper Creek CS-60 | EVSEupgraded 2013 Leaf EVSE | 3.84kw PV

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