2 Poel GFCi Breaker on Multi wire split recep. kitch. ci

[mcgroh]

Performed some kitchen remodeling with new fixtures & added outlets to exisiting kitchen 20 amp circuit with a shared neutral. Originally had split receptacles, i.e. one circuit on lower half of duplex, second circuit on upper half. I maintained that configuration.

Now I want to add GFCI protection so I went to the forum and looked at the archives - very confusing and far from a unanimity of opinion on this subject! It did seem that if I wanted to do this, esp. given the split receptacle configuration, my only option was a 2 pole 20 amp GFCI Breaker which I purchased and installed.

It didn't work. As soon as power feeds the breaker it trips. This particular breaker (Siemens)has terminals for each of the power loads and the load neutral. There is also a heavy gauge white lead which is terminated at the neutral bus.

Next I started trouble shooting. Since this installation works fine with a regular 20 amp breaker (single pole on each load phase) I didn't think the problem was in the load side wiring. I checked my connections at the panel - the breaker keeps tripping. Next I re-instlalled the single pole breakers and took a reading on the gounded conductor looking for current which might have tripped the GFCI. Less than a .1 amp so I assume this confirms my instinct that the wiring isn't faulty or I have an existing ground fault in the circuits.

As I see it there are three options: 1. The breaker is defective or 2. I cannot put GFCI protection on this type of circuit (how can that be - I thought that is what this breaker configuration was all about) or 3. I've got some sort of wiring problem to the outlets and luminaries on this circuit which isn't causing a problem with regular breakers but is tripping the GFCI. I need you input. Hopefully the wise heads on this forum can point me in the right direction.

Thanks.

 

[jimwalker]

Re: 2 Poel GFCi Breaker on Multi wire split recep. kitch. ci

If you read any current with no load then i think there is a wiring problem.Why not just use gfci receptacles

 

[don_resqcapt19]

Re: 2 Poel GFCi Breaker on Multi wire split recep. kitch. ci

If you want to split wire the kitchen counter receptacles, you are correct that the only way this can be done is by using a 120/240 volt 2 pole GFCI breaker. If the breaker is not defective, the most common cause for tripping would be an EGC touching the neutral.
Don

 

[stars13bars2]

Re: 2 Poel GFCi Breaker on Multi wire split recep. kitch. ci

Don
Why can't I do this with two GFCI receptacles?

 

[jimwalker]

Re: 2 Poel GFCi Breaker on Multi wire split recep. kitch. ci

You could use 2 gfci receptacles.And it would be cheaper and better for customer by having the reset in kitchen.Some warning first.You may need to use more than 2 depending on how they were layed out.And chances are high that there is a problem as already mentioned with neutral and grounds touching.This still needs fixed.

 

[don_resqcapt19]

Re: 2 Poel GFCi Breaker on Multi wire split recep. kitch. ci

The original poster said he was "split wiring" the duplex receptacles. The GFCI protection must be on the line side of the split wired receptacles, as they don't make GFCI duplex receptacles that can be split wired. Yes you could use 2 standard GFCIs set up as "feed through" to feed the split wired receptcles, but you would have to break off both tabs and run two hots and two neutrals to each receptacle. In my opinion, there is a wiring problem on the load side of the GFCI breaker, and until this problem is fixed, any type of GFCI that is installed will trip.
Don

 

[mcgroh]

Re: 2 Poel GFCi Breaker on Multi wire split recep. kitch. ci

O.K so far the consensus is I my have a wiring problem. Le me clarify one thing: When I tested the ECG to see if there was any current I did have a load on both circuits. It tested less than .1 amp. Is this significant enough to suspect a neutral/EGC short as has been suggested. IF I had neutral/EGC contact wouldn't the amperage have tested higher? Furthermore, is it sufficient to trip the GFCI?

I appreciate the suggestion to use separate GFCI devices at the outlet but as I indicated, this was already wired for split receptacles and although I could have used two GFCI (one per circuit) I couldn't run separate neutrals. Also, by running separate neutrals doesn't this negate one of the advantages of the 3 wire circuit?

 

[don_resqcapt19]

Re: 2 Poel GFCi Breaker on Multi wire split recep. kitch. ci

mcgroh,
0.1 amps is 20 times the trip point of a GFCI. They trip at ~0.005 amps (5 mA).
Don

 

[jimwalker]

Re: 2 Poel GFCi Breaker on Multi wire split recep. kitch. ci

The common neutral will not effect the line side of the gfci receptacle.Everything down stream from that gfci recept load side will have a sepearte neutral.

 

[hurk27]

Re: 2 Poel GFCi Breaker on Multi wire split recep. kitch. ci

mcgroh
The first thing I would look for is another circuit neutral connected to this neutral you can do this at the panel by lifting the neutral off the GFCI breaker make sure there is no loads pluged in and use a continuty tester to see if there is any connection to the neutral bar. If there is then you have a down streem neutral connection somwhere. And this will also show a grounded neutral also so both will have to be checked for.
This circuit will work if the wires are right.

Make sure you replace the neutral before turning the GFCI breaker back on.

 

[stars13bars2]

Re: 2 Poel GFCi Breaker on Multi wire split recep. kitch. ci

Don
Sorry, I overlooked the split wire part. I was just thinking about what I would do in this situation, not what you both said.

 

[jeff43222]

Re: 2 Poel GFCi Breaker on Multi wire split recep. kitch. ci

I think the problem is with the shared neutral. The whole idea of a GFCI is for it to trip when the incoming hot and outgoing neutral current vary, indicating that the current is going somewhere it's not supposed to. But if there is a separate circuit using the same neutral, it's going to cause some activity on the neutral that the GFCI on the first circuit will notice, and it will interpret this as a ground fault. Sure, it's only 0.1A, but another way of saying that is that it's 100mA. That's way more than is needed (4-6 mA) to trip a GFCI.

This is yet another reason I refuse to share neutrals between circuits. Sure, it's more convenient when running the wire, but then you run into these kinds of problems. Also, if the neutral gets disconnected somewhere, the two 120A parallel circuits suddenly become one 240A series circuit. Not a good thing for most electrical devices.

-Jeff

 

[don_resqcapt19]

Re: 2 Poel GFCi Breaker on Multi wire split recep. kitch. ci

Jeff,
That is not how a GFCI works. It compares the load side current of both the hot and the neutral. The use of a shared neutral on the line side does not have any effect on the operation of a GFCI. If it did, then GFCIs would never work, as all services have a shared neutral.
Don

 

[mcgroh]

Re: 2 Poel GFCi Breaker on Multi wire split recep. kitch. ci

Oh Boy! This isn't easy is it! O.K. I haven't had a chance to track down the wiring on the load side of the breaker, essentially every duplex and luminary on these two circuits. For now I have the conventional breakers installed and the circuit(s) are working fine but I still want GFCI Protection. I am trying to get an idea of what to look for from the suggestions on this list. I am, to say the least, a bit confused and if you've read all these posts I'm sure you'll understand why.

With a GFCI Breaker isn't everything beyond the panel on the load side? Therefore, because this is a three wire circuit isn't the neutral shared by the two circuits? Furthermore because they are opposite phases, in theory if the two loads are equal the neutral will carry no current at all. I understand the EGC / Neutral contact as a problem and I've mapped out a strategy for tracking this but this "Shared Neutral" the posts have mentioned I don't understand. Of course the neutral is shared by both "Hots" on each duplex, all the way back to the panel and the breaker. Therefore, I suppose a GFCI Breaker cannot function the same as a GFCI Receptacle where only a single circuit is typically involved. I used this special two-pole GFCI Breaker because it was intended for this use and therefore the shared neutral on the "load" side wouldn't be a problem because it is indigenous to this type of circuit wiring which we all know is common for kitchen small appliance circuits.

 

[charlie]

Re: 2 Poel GFCi Breaker on Multi wire split recep. kitch. ci

I think I see where your confusion lies. The circuit is all three conductors (both phases and the neutral). The GFCI is looking at the imbalance between all three of these conductors. Assuming 4 amperes on one phase and 3 amperes on the other phase and 1 ampere on the neutral. The 120/240 volt circuit is balanced and the GFCI will not operate even though there is 1 ampere on the neutral and 4 amperes on one phase.

Take a look at how a GFCI operates.

 

[mcgroh]

Re: 2 Poel GFCi Breaker on Multi wire split recep. kitch. ci

Thanks Charlie It makes sense and I appreciate the link to the GFCI explanatory info.

I will begin the laborious task of tracking down this problem and I'll post the outcome to the list.

My gut is I've got a neutral to EGC or neutral to box fault(these are all metal boxes which are bonded).

Thanks again!

 

[hurk27]

Re: 2 Poel GFCi Breaker on Multi wire split recep. kitch. ci

mcgroh
What you have is a shared neutral on the load side of the GFCI circuit. This can only be done with a two-pole GFCI breaker or by placing a GFCI receptacle in each circuit at the first point the two circuits break apart. But since you have split receptacles then even that can not be done. you will eather have to use a GFCI receptacle at each point of use or rewire the circuit after it enters the room to seperate the two circuits. The only other way is to obtain a two-pole 20 amp common trip GFCI breaker listed for the panel you have.

What Charlie was trying to say is with a shared neutral the current will never be balanced between the hot and neutral at each GFCI breaker. since each circuit load will remove current on the neutral there will always be less current on the neutral than on each hot for that breaker. And this imbalance is what causes the coil in the GFCI to trip the breaker.

Let's use the 3 amp 4 amp example.
phase A has 3 amps and phase B has 4 amps as Charlie said the neutral will now have 1 amp on it but one hot will have 3 amps and the neutral only has 1 amp this will look like a ground fault to the GFCI because not all of the current is returning to the GFCI through the neutral as some is returning through the hot of the other circuit, just like if the hot had leakage to ground or another circuit conductor. The same is true for the other circuit as some of it's current is returning through the first circuit hot. With a two-pole GFCI both hots and the neutral all run through the same coil so any load current will always cancel out the the returnning current. and if any current does not return through this coil then it will open the circuit,
Hope this helps.
Wayne

[ June 17, 2004, 12:54 AM: Message edited by: hurk27 ]

 

[mcgroh]

Re: 2 Poel GFCi Breaker on Multi wire split recep. kitch. ci

Hurk

Thanks but I got Charlie's excellent example and explanation and I have been trying to use a two pole breaker GFCI all along. I knew from the beginning with the split receptacle configuration I wasn't going to be able to use GGCI outlet(s).

The problem is my GFCI breaker trips immediately upon energizing it so I've got some sort of fault downstream which I will have to track down or, the other possibility is I've got a faulty breaker. The list seems to not favor the latter option however because I do have current flowing on the EGC when all loads are off.

What was confusing to me resulted from the obvious prejudice the list had for using GFCI receptacles vs. a GFCI Breaker. I got lots of misleading information from well intentioned members who nevertheless confused the issue by suggesting methods clearly related to the use of Receptacles not Breakers. None of this made sense until Charlie took the time to explain the TOTAL circuit monitored by the Breaker consitists of both phases and the neutral.

 

[awr]

Re: 2 Poel GFCi Breaker on Multi wire split recep. kitch. ci

Originally posted by jeff43222:


This is yet another reason I refuse to share neutrals between circuits. Sure, it's more convenient when running the wire, but then you run into these kinds of problems. Also, if the neutral gets disconnected somewhere, the two 120A parallel circuits suddenly become one 240A series circuit. Not a good thing for most electrical devices.

-Jeff

A balanced 3-wire circuit Is a series 240 [V] circuit... if the neutral has no current than there is no difference from a 240V series circuit... of course... if the load isn't balanced and the neutral was disconnected, i suppose the high resistance side would get a voltage spike it would not like too much... however there is an elegance to 3-wire circuits that i can't pass up.

I love the idea of splitting the top n bottom receptacles of a duplex to different circuits...

In this problem, you need to start with no load... you are saying there is an imbalanced load (100mA on the neutral).. this should not be a problem for the 2-pole GFCI breaker since it's adding up the total load and total neutral.. if there is a .1A neutral current there is a load... find and remove the load and start from there... if ckt pops with no load, there is a short someplace most likely.

If you get it working with no load, add loads 'til it pops.. probably a problem with the device like a shorted neutral to ground.

Good luck keep us posted.

-awr