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Old 08-15-2014, 03:17 PM   #11
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Quote:
Originally Posted by trimixdiver1 View Post
If you switch the neutral, then yes it will trip. A GFI monitors the Hot and Neutral lines, not ground.
that is my understanding of it too. it makes sure that the incoming current (hot side) is within 5mA of the outgoing current(neutral side). if there is an imbalance, then it trips.

I assume with a 240volt GFCI, that it works the same, just monitors the two hot legs instead. So if you switch a leg to nuetral, then all the current will be sourced by one of the hot legs and returned by the neutral. The 240 volt GCFI will see this as an imbalance and trip.
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Old 08-15-2014, 03:19 PM   #12
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Quote:
Originally Posted by Malticulous View Post
A GFCI only trips if there is current on the ground. A 30A/250v SPDT switch would do the job. If the switch stops on center you could even have an off position (don't forget the other leg on the element is still live but the circuit is broke.). It's not much different than a 3-way light switch.
WRONG

A GFCI trips on an imbalance of current on the Hot and Neutral lines. Ground isnt even needed when using a GFCI

NEC 406.3
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Old 08-15-2014, 03:22 PM   #13
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Quote:
Originally Posted by Minbari View Post
that is my understanding of it too. it makes sure that the incoming current (hot side) is within 5mA of the outgoing current(neutral side). if there is an imbalance, then it trips.

I assume with a 240volt GFCI, that it works the same, just monitors the two hot legs instead. So if you switch a leg to nuetral, then all the current will be sourced by one of the hot legs and returned by the neutral. The 240 volt GCFI will see this as an imbalance and trip.
A 240v breaker still monitors the neutral (you loop the neutral through the breaker then to the neutral buss bar) It monitors both Hot lines against the Neutral for imbalance.
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Old 08-15-2014, 03:25 PM   #14
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Quote:
Originally Posted by trimixdiver1 View Post
A 240v breaker still monitors the neutral (you loop the neutral through the breaker then to the neutral buss bar) It monitors both Hot lines against the Neutral for imbalance.
ah, ok. never have wired a 240 volt GFCI, so I was doing a bit of guess work. thanks for the info.

the principal is the same though, right? switching the output from 240 volt to 120 volt would cause an imbalance on the neutral and trip it.
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Old 08-15-2014, 03:36 PM   #15
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Quote:
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ah, ok. never have wired a 240 volt GFCI, so I was doing a bit of guess work. thanks for the info.

the principal is the same though, right? switching the output from 240 volt to 120 volt would cause an imbalance on the neutral and trip it.
It should yes. Some GFCI are more tolerant then the next, but "single phasing" a 240v load will trip it more than likely.
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Old 08-15-2014, 04:43 PM   #16
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My understanding with a properly wired, H1-H2-N GFCI, with H1 used for deriving the 120v circuit, is that the load must balance across all three. On at 240v, H1 must balance H2, as N is at 0. On at 120v, H1 and N must balance, as H2 is at 0. On at both 120v and 240v, H1 must balance H2 + N. Off, everything is at 0. So I would expect it to not trip the GFCI as long as you switched through off when switching between 120v and 240v, which you should be doing anyway as you would not want both H2 and N live at the element at the same time. That said, I have never tried it.

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Old 08-15-2014, 04:49 PM   #17
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The goal of a GFCI is to insure that all current going out on either of the phases returns either through the other phase or the neutral. Thus it sums the currents in the two phases and the neutral. If the sum isn't 0 (i.e. there is leakage through earth or any other path) then it trips.

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Old 08-15-2014, 07:03 PM   #18
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While this is a very informative discussion of GFI's, 120V and 240V, the simple fact remains that a 5500w element at 120V is not enough wattage to boil more than a gallon or two in a small pot, less or even maybe zero in a large kettle. 5500/4 is only 1375 watts, next to nothing and NOT enough!

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This can be done by simply using a large enough kettle, and sizing the element to the kettle and batch size to produce a reasonable boil at 100% element power
Varying batch size is not ideal with a simple e kettle.

IME, 4000 watts will work pretty well for 10 gallon batches, and 3000w for 5 gallon batches.
Or you can run a large 5500w with a simple PWM controller, or a PID and SSR.
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Old 08-15-2014, 11:01 PM   #19
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Quote:
Originally Posted by trimixdiver1 View Post
WRONG

A GFCI trips on an imbalance of current on the Hot and Neutral lines. Ground isnt even needed when using a GFCI

NEC 406.3
Yes, for it to trip there must be current flowing to a ground somehow, hence a ground fault.

I can boil a five gallon batch fairly well with one of my 2350w burners on my electric stove top. Your element has to be more efficient than that. Maybe not a 1000 watt more. A heat stick could make the difference.
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