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Old 11-03-2009, 05:05 AM   #1
Number21
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Default Can I put two GFCIs on one circuit?

I just moved into a shop with really scary and hazardous wiring from the previous occupant. After ripping all that off the walls, I'm left with two outlets in the entire place that work. Both are hooked to the same 20A circuit, the power conduit runs down from the ceiling into a junction box, where it "T's" off into two outlets about 10' from the middle.

As far as I can tell I've got hot/neutral/gnd coming from the ceiling in the junction box. Then, the hot/neutral/gnd split up and go to each outlet.

Anyway, I installed a GFCI outlet in both sides, because the old outlets were crap and I had some nice new 20A GFCI outlets already. When I turned the power back on, one GFCI worked, but the other didn't. It shows 120v between ground and neutral. WTF? I didn't have a lot of time to try and trace the wires but everything seems right.

Is it a problem trying to install two GFCIs on one circuit like this? I guess the more correct way to do it would be to add a GFCI outlet at the junction box, and then two regular outlets on both ends.
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Old 11-03-2009, 05:20 AM   #2
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Default Re: Can I put two GFCIs on one circuit?

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Originally Posted by Number21 View Post
I just moved into a shop with really scary and hazardous wiring from the previous occupant. After ripping all that off the walls, I'm left with two outlets in the entire place that work. Both are hooked to the same 20A circuit, the power conduit runs down from the ceiling into a junction box, where it "T's" off into two outlets about 10' from the middle.

As far as I can tell I've got hot/neutral/gnd coming from the ceiling in the junction box. Then, the hot/neutral/gnd split up and go to each outlet.

Anyway, I installed a GFCI outlet in both sides, because the old outlets were crap and I had some nice new 20A GFCI outlets already. When I turned the power back on, one GFCI worked, but the other didn't. It shows 120v between ground and neutral. WTF? I didn't have a lot of time to try and trace the wires but everything seems right.

Is it a problem trying to install two GFCIs on one circuit like this? I guess the more correct way to do it would be to add a GFCI outlet at the junction box, and then two regular outlets on both ends.
Shouldn't be any problem putting 2 different GFCI outlets on one circuit. IF you indeed have 120 volts between ground and neutral I suspect you have it wired wrong, hot to the neutral seems like the likely issue.
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Old 11-03-2009, 05:57 AM   #3
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Default Re: Can I put two GFCIs on one circuit?

Yeah, it must be wired wrong, but I don't understand how. All the colors match up and it looks like a continuous run. I didn't have time to take apart the junction box and trace out each wire though...

The wires for the outlet that works are simply wire-nutted to the same color wires for the other outlet. (3 wires total, one incoming, 2 outgoing, per color)

You'd be horrified at what this guy did to the electrical though...

Last edited by Number21; 11-03-2009 at 06:00 AM.
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Old 11-03-2009, 06:19 AM   #4
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Default Re: Can I put two GFCIs on one circuit?

I was watching Holmes on Homes the other day and he was talking about GFCI's and stated that two on the same circuit is a no-no as one would trip the other. One per circuit only.
Not that I know, but just going on what he stated.
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Old 11-03-2009, 06:33 AM   #5
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Default Re: Can I put two GFCIs on one circuit?

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I was watching Holmes on Homes the other day and he was talking about GFCI's and stated that two on the same circuit is a no-no as one would trip the other. One per circuit only.
Not that I know, but just going on what he stated.
I think you're right. I've got two outside GFCI outlet's wired on the same circuit outside and it does seem like when one trips I have to reset both. No biggie since they are right next to each other but still I see where it could be a pain.
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Old 11-03-2009, 07:11 AM   #6
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Default Re: Can I put two GFCIs on one circuit?

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Is it a problem trying to install two GFCIs on one circuit like this? I guess the more correct way to do it would be to add a GFCI outlet at the junction box, and then two regular outlets on both ends.
It should not really be a problem but it is not necessary. If you install a GFCI outlet first, everything after it is protected. You are either wired wrong, have a bad wire or have a bad outlet. Disconnect the outlet and test again.
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Old 11-03-2009, 07:26 AM   #7
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Default Re: Can I put two GFCIs on one circuit?

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I was watching Holmes on Homes the other day and he was talking about GFCI's and stated that two on the same circuit is a no-no as one would trip the other. One per circuit only.
Not that I know, but just going on what he stated.
That would be 2 in series, one feeding the other one
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Old 11-03-2009, 08:23 AM   #8
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Default Re: Can I put two GFCIs on one circuit?

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That would be 2 in series, one feeding the other one
Correct...these are in parallel. They should function properly.
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Old 11-03-2009, 09:15 AM   #9
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Default Re: Can I put two GFCIs on one circuit?

Did you attach to the "load" side screws on the GFI? That'll cause problems.
But, if the wires are attached to the line side screws with the black wire to the brass screw, white wire to the silver and you measure 120v between them, the GFI is junk.

Quote:
Originally Posted by Kevin54 View Post
I was watching Holmes on Homes the other day and he was talking about GFCI's and stated that two on the same circuit is a no-no as one would trip the other. One per circuit only.
Not that I know, but just going on what he stated.
There is no problem with putting more than one GFI on a circuit.
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Old 11-03-2009, 11:19 AM   #10
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Default Re: Can I put two GFCIs on one circuit?

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Did you attach to the "load" side screws on the GFI? That'll cause problems.
But, if the wires are attached to the line side screws with the black wire to the brass screw, white wire to the silver and you measure 120v between them, the GFI is junk.



There is no problem with putting more than one GFI on a circuit.

+1 This is what my electrician told me to do, as I want to add an outside outlet, without having to go back in to reset the GFCI.
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Old 11-03-2009, 11:42 AM   #11
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Default Re: Can I put two GFCIs on one circuit?

Best thing to do is pigtail to a GFI if you want to put more then one on a circuit.

Warning only do this if you want that outlet to trip. If you want the outlets after the GFI to trip then you must run the outlet in and out.
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Old 11-03-2009, 11:56 AM   #12
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Default Re: Can I put two GFCIs on one circuit?

I used gfi outlets most of the time in my old shop as I was just learning to wire I am still no electrician and these are lableled very clearly which side is in, which is out and which color wire goes where. for newbies running wiring it is easy and I can certainly tell you that there is no problem running multiple gfi outlets on the same circuit. the most likely problem from my experience is that in the junction box there is a wire nut with one of the wires crossed or loose. assuming of course that you wired the outlet correctly.
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Old 11-03-2009, 12:08 PM   #13
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Default Re: Can I put two GFCIs on one circuit?

Tape around the GFI outlet also before you stuff it back into the box. I have seen ground wires touch more then they should because the GFI takes up a lot more space then a normal outlet does.
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Old 11-03-2009, 12:28 PM   #14
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Default Re: Can I put two GFCIs on one circuit?

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Originally Posted by Kevin54 View Post
I was watching Holmes on Homes the other day and he was talking about GFCI's and stated that two on the same circuit is a no-no as one would trip the other. One per circuit only.
Not that I know, but just going on what he stated.

What Mike was speaking about is having one GFCI fed from the "load" terminals of the first GFCI. This results in nuisance tripping. However, if both GFCIs are fed from the line directly there is no such issue.

I did this exact scenario in a bathroom I completed because one GFCI was in the closet while the other was next to the vanity. I knew where they both were, but a visitor or future homeowner might not, and I didn't want to confuse someone when they couldn't figure out why the outlet wasn't working.

Using multiple GFCIs on one circuit is actually a good idea, but in some cases it might be easier (and cheaper) to simply install a GFCI breaker. If the panel is in the basement while the receptacles in question are in the garage, then having GFCI receptacles is probably the best solution just to prevent a person from having to go all the way into the basement to reset them if/when they trip.
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Old 11-05-2009, 05:48 AM   #15
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Default Re: Can I put two GFCIs on one circuit?

Well, I took apart the junction box and decided to just use a GFCI outlet there as the junction. Now the outlets on both ends are connected to it, and I have another outlet in the middle.

I still don't know why it didn't work before though, all the colors and wires matched up like they should? Oh well, it works now...
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Old 11-05-2009, 06:18 AM   #16
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Default Re: Can I put two GFCIs on one circuit?

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Yeah, it must be wired wrong, but I don't understand how. All the colors match up and it looks like a continuous run. I didn't have time to take apart the junction box and trace out each wire though...
If it is correct leaving the junction box but wrong entering the outlet box, the most likely reason is that there's a box somewhere that you haven't discovered. If this is a run in conduit, he could have spliced the wires inside the conduit (illegal).

Regarding GFCI's - you can use them on multiple receptacles, and in your case, where the feeder splits and goes to 2 boxes instead of looping from one to the other, you'd have to - unless you wanted to install a GFCI circuit breaker. Note that you can't connect any other GFCI devices via the "load" terminals of a GFCI receptacle. However, anything connected to the "load" terminals will be protected, and the extra "Protected by GFCI" labels that came with the GFCI device should be applied to all of the downstream receptacles.
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Old 01-27-2014, 08:44 PM   #17
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Question Re: Can I put two GFCIs on one circuit?

I am not a professional electrician, but I have never heard the term "series" related to an AC house wiring circuit. Its my perception they are all "parallel"?
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Old 01-27-2014, 08:52 PM   #18
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Default Re: Can I put two GFCIs on one circuit?

The question is why? Why 2 when one will protect a whole circuit if it is first in series and wired properly?

Why do something funky?

The smallest stupidist thing can burn a house to the ground. Mother in laws house went last year. 400k in damage to property and contents. Because someone laid a wire run over a metal truss connector 30 years ago. Finally wore through. Poof.
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Old 01-27-2014, 08:52 PM   #19
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Default Re: Can I put two GFCIs on one circuit?

You mentioned that there were a lot of wiring problems in the place. I assume you already checked, but they hooked the hot wire up correctly in the distribution panel right?
In my county, you don't really have to get electrical inspected (if you live outside city limits). Some jackass decided that you should wire up black to the breaker on one side of electrical panel, and white to the breaker on the other side of panel.

Know how I figured it out. Wiring up a ceiling fan with the switch off, checked to make sure black wasn't hot, proceeded to wire up, and BOOM white bit me. I was dumb ass to not check both wires, but I never did that again.
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Old 01-27-2014, 09:28 PM   #20
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Default Re: Can I put two GFCIs on one circuit?

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Originally Posted by LennyTheLizard View Post
You mentioned that there were a lot of wiring problems in the place. I assume you already checked, but they hooked the hot wire up correctly in the distribution panel right?
In my county, you don't really have to get electrical inspected (if you live outside city limits). Some jackass decided that you should wire up black to the breaker on one side of electrical panel, and white to the breaker on the other side of panel.

Know how I figured it out. Wiring up a ceiling fan with the switch off, checked to make sure black wasn't hot, proceeded to wire up, and BOOM white bit me. I was dumb ass to not check both wires, but I never did that again.
Thread is 5 years old. Probably figured it out by now. But for future use see the picture:
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