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-   -   40 amp double pole gfci problem (http://www.diychatroom.com/f18/40-amp-double-pole-gfci-problem-23620/)

rivers 07-13-2008 04:47 PM

40 amp double pole gfci problem
 
Hello:
My mother has a sub panel that runs from her house to a pool house via a 40 amp breaker which was on a non gfci breaker. I installed a gfci breaker and it works fine when the pool pump and booster pump is on (both seperate 20 amp double pole breakers). However, when you flip other breakers in the box for inside lighting etc. it trips. It even trips if the pumps are not on. The two 20 amp double pole breakers are on the left side of the sub panel and four 20 amp singles are on the right if this makes any difference. Any suggestions as to the problem?

wirenut1110 07-13-2008 05:21 PM

Your 2 240 volt loads arent using a neutral but your 120 volt circuits are. I would put the 40 amp breaker back and feed any additonal loads with their respective gfi's if required.. The imbalance on your 120 loads are tripping the breaker.

Speedy Petey 07-13-2008 06:33 PM

Wirenut, this is not true. A 2-pole GFI breaker monitors both 120 and 240v loads at the same time. It is quite common to have a 2-pole GFI feeder breaker feeding a pool panel as in the OP's situation.

There is a fault in the lighting circuits somewhere.

wirenut1110 07-13-2008 06:36 PM

If he has 4 single pole breakers in there and the neutral isn't balanced, this won't cause it to trip? I love this, I learn something new everyday. Sorry Rivers, I stand corrected.

wirenut1110 07-13-2008 06:48 PM

In that case, you'll need to turn them on 1 at a time to isolate the circuit that's tripping it, then check out things that are on it that circuit.

Speedy Petey 07-13-2008 07:30 PM

Quote:

Originally Posted by wirenut1110 (Post 138830)
If he has 4 single pole breakers in there and the neutral isn't balanced, this won't cause it to trip? I love this, I learn something new everyday. Sorry Rivers, I stand corrected.

The neutral will carry all the imbalance and it should still not trip.

Here is a VERY simplistic example:

Leg "A&B"
2p20 carrying 15A - spaces 1&3
2p20 carrying 10A - spaces 2&4

Leg "A"
sp20 carrying 5a - space 5
sp20 carrying 5A - space 6

Leg "A" sees 35A
Leg "B" sees 25A
The neutral sees 10A

Any imbalance in this scenario, such as the neutral seeing less than 10A, or leg "A" seeing less than 35A would mean there is a ground fault somewhere.

chris75 07-13-2008 08:20 PM

The biggest problem I see with doing a entire panel fed from a gfci breaker is that there could be a little current leakage on each breaker, so it could happen to add up to 5 miliamps...

rivers 07-13-2008 08:45 PM

Thanks for the replies:
After I installed the gfi I turned on the two pumps and it worked fine. Even with the pumps turned off, when you turned on any of the 20 amp breakers it would trip the main 40 gfi. I might also mention that two of the 20 amp breakers in the sub panel are also gfi's. Does this make a difference? If one of these gfi's single pole breakers is bad would this make the main gfi in the house trip regardless of being turned on? Why would the two 20 amps work and not the 20s? Confused:wink:

chris75 07-13-2008 09:15 PM

so you tried every single pole breaker and no matter which one you turn on the 40 amp gfi main trips?

rivers 07-13-2008 09:22 PM

Sorry for the confusion.
In the sub panel there are 4 20 amps on the right side, two gfi's, two regulars. On the left are the pump breakers. Any of the 20's that are turned on trips the gfi in the main in the house. The left side where the pump breakers are works fine.

chris75 07-13-2008 09:23 PM

Quote:

Originally Posted by rivers (Post 138874)
Sorry for the confusion.
In the sub panel there are 4 20 amps on the right side, two gfi's, two regulars. On the left are the pump breakers. Any of the 20's that are turned on trips the gfi in the main in the house.

any pics of the panels?

rivers 07-13-2008 09:32 PM

Sorry, no.

BigJimmy 07-13-2008 09:50 PM

Ok, here's a question that may be stupid but I have to ask. A 2p GFCI can be wired to serve a single phase 240V load (no neutral), a 3w MWBC or a 120/240 load as is your case. In the first example, the neutral tail from the GF device is connected to the neutral bus but there is no connection from the field (obviously). In the last two examples, the load neutral needs to be connected to the neutral terminal on the GF breaker (in addition to the breaker's neutral pigtail being terminated on the neutral bus).

Before you began/changed from normal 2p-40 breaker to GFCI variety, the neutral from the feeder to the subpanel was terminated to the neutral bus in the main panel. When you installed the 2p 40A GFCI breaker in the main, did you relocate the feeder neutral to the GF breaker terminal (and connect the breaker's white neutral wire to the neutral bus, in place of the feeder neutral)? If you did not do this, the 240V loads switched on by themselves would work fine. However, as soon as you'd turn on either 1p breaker in the subpanel, the GF would trip since it would see the 1ph-120V current leaving either A or B terminals but would see nothing returning, resulting in an immediate trip. This would be similar to instances where someone installed a 1p GFCI breaker and connected the branch circuit neutral to the bus, instead of the breaker (it will trip immediately).

I really think that this smells like an incorrectly wired GF breaker.

Please check the connections and let us know. Remember, the feeder neutral connects to the GFCI breaker and then the breakers white neutral sense wire connects to the panel's neutral bus.

For some additional information, you can go to http://ecatalog.squared.com/pubs/Cir...0730CT9801.pdf and see pages 10 and 11 of the .pdf.

TTFN,
Jimmy

chris75 07-13-2008 10:00 PM

Quote:

Originally Posted by BigJimmy (Post 138887)
Ok, here's a question that may be stupid but I have to ask. A 2p GFCI can be wired to serve a single phase 240V load (no neutral), a 3w MWBC or a 120/240 load as is your case. In the first example, the neutral tail from the GF device is connected to the neutral bus but there is no connection from the field (obviously). In the last two examples, the load neutral needs to be connected to the neutral terminal on the GF breaker (in addition to the breaker's neutral pigtail being terminated on the neutral bus).

Before you began/changed from normal 2p-40 breaker to GFCI variety, the neutral from the feeder to the subpanel was terminated to the neutral bus in the main panel. When you installed the 2p 40A GFCI breaker in the main, did you relocate the feeder neutral to the GF breaker terminal (and connect the breaker's white neutral wire to the neutral bus, in place of the feeder neutral)? If you did not do this, the 240V loads switched on by themselves would work fine. However, as soon as you'd turn on either 1p breaker in the subpanel, the GF would trip since it would see the 1ph-120V current leaving either A or B terminals but would see nothing returning, resulting in an immediate trip. This would be similar to instances where someone installed a 1p GFCI breaker and connected the branch circuit neutral to the bus, instead of the breaker (it will trip immediately).

I really think that this smells like an incorrectly wired GF breaker.

Please check the connections and let us know. Remember, the feeder neutral connects to the GFCI breaker and then the breakers white neutral sense wire connects to the panel's neutral bus.

For some additional information, you can go to http://ecatalog.squared.com/pubs/Cir...0730CT9801.pdf and see pages 10 and 11 of the .pdf.

TTFN,
Jimmy

Nice post :thumbsup: I thought a pic of his panel would easily show the problem. :)

BigJimmy 07-13-2008 10:02 PM

Quote:

Originally Posted by chris75 (Post 138892)
Nice post :thumbsup: I thought a pic of his panel would easily show the problem. :)

Oh, go on!:laughing:

Thanks, bro!


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