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Old 01-11-2009, 07:16 PM   #16
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Originally Posted by Mobjack Pete View Post
I don't need 240volts. Can I feed the two 20amp GFCI breaker from a single 120volt black (from 8/2) with a jumper to second breaker hot lug?
NO!!! you will short it out no question asked.
You will need a 20 amp single pole GFCI breaker for this useage however you will may have to make a pigtail to fit in the termation at the breaker due some of the breaker will not take #8 to fit in depending on which brand name it is.

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I know to keep the neutral bus separate from ground. The white (from 8/2) goes to neutral bus, and the ground (bare copper in 8/2) goes to a ground block secured to the metal sub-panel, further grounded to the rod under pier...as much for lightening protection as for ground purposes. At present, this is what I have hooked up and cannot get the first 20amp GFCI breaker to set. What is wrong?
Did you have green bonding screw or bonding strap in the breaker panel ? If that the case you will have to remove it and the last thing is how far is this subpanel is from the main breaker box is ??

Merci,Marc

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Old 01-11-2009, 07:21 PM   #17
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GFCI Power Usage


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Originally Posted by Mobjack Pete View Post
I don't need 240volts. Can I feed the two 20amp GFCI breaker from a single 120volt black (from 8/2) with a jumper to second breaker hot lug?
I know to keep the neutral bus separate from ground. The white (from 8/2) goes to neutral bus, and the ground (bare copper in 8/2) goes to a ground block secured to the metal sub-panel, further grounded to the rod under pier...as much for lightening protection as for ground purposes. At present, this is what I have hooked up and cannot get the first 20amp GFCI breaker to set. What is wrong?
Don't jumper the second bus. Just put the second breaker on the same bus as the other one. Try that and see what happens.
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Old 01-11-2009, 07:26 PM   #18
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Originally Posted by jerryh3 View Post
Don't jumper the second bus. Just put the second breaker on the same bus as the other one. Try that and see what happens.

Jerry.,

I hate to be harsh but It is not a pratical idea to do this at all for safety reason if someone get a idea to do this and what will happend is that when someone turn off the breaker at one spot and the circuit is still engerized then have to find a second breaker to kill it to make sure the circuit is dead.

That the reason why I don't encorge this trick

To OP., with two pole breaker you can have one hot conductor hook up and leave the second pole alone if nothing else is hook up that is fine with that part.

Merci,Marc
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Old 01-11-2009, 07:32 PM   #19
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GFCI Power Usage


frenchelectrician, do you mean a two pole GFCI...the two-in-one kind?
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Old 01-11-2009, 08:02 PM   #20
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Here what the 2 pole GFCI look like

This breaker is QO series the other namebrand may look not the excat the same but you will get the idea.

Merci,Marc
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Old 01-11-2009, 08:10 PM   #21
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Marc, he is not using two breakers to power the subpanel. He is sending 120 V to the subpanel on 8-2. He has 2 GFCI single poles at the subpanel that keep tripping. Apparently the circuits work on non-GFCI breakers. My guess is that you actually have a ground fault that needs to be addressed somewhere in your circuits.
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Old 01-11-2009, 08:14 PM   #22
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Originally Posted by Gigs View Post
I measured a cheap harbor freight GFCI at 6.1 milliamps with nothing plugged into it.
Gigs, At 120V this works out to 732mW which is in the ballpark for the commonly used GFCI chip LM1851 which has a max power rating at 1250mW.
LM1851.pdf (application/pdf Object)

Here is a schematic of a sample GFCI circuit that uses the LM1851 chip. The schematic is on page 7 of the pdf:
UTC LM1851

I don't see anything on that schematic that would cause a surge over 250mA. I suspect the metering circuit. Perhaps you could verify this by instead of the ammeter,connect an analog AC voltmeter across a series limiting resistor to the GFCI.

Gigs, Excuse Mobjack as a newbie he does not know that when asking a question, he should start a new thread. Not jump into the middle of your thread.
MEMBERS, Dont' reply to Mobjack...He needs to start his own thread

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