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wiring multiple GFCI protected outlets on 10/3 cable

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Forum topic by HokieMojo posted 03-19-2010 05:14 PM 7880 views 0 times favorited 14 replies Add to Favorites Watch
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HokieMojo

2103 posts in 3193 days


03-19-2010 05:14 PM

I’m going to use 10/3 cable to wire up some GFCI protected outlets in my garage shop. The plan is to split the two hot wires into two separate circuits (protected on one double pole, single switch breaker). Is there a way to do this where the first outlet on each circuit will be a GFCI and the rest will be GFCI protected, but use a standard outlet?

I know how to wire a GFCI outlet on each outlet, or to wire a single circuit using 10/2 cable and get downstream protection, but I can’t seem to find any guidance on doing this with 10/3. I think it might be impossible.
Thanks!


14 replies so far

View TheDane's profile

TheDane

4997 posts in 3128 days


#1 posted 03-19-2010 05:29 PM

Make first receptacle on the circuit a GFCI and come from the load side to feed the others. That way, the rest can just be standard receptacles. The GFCI will trip if any downstream outlets has a problem.

Putting multiple GFCI’s on one circuit can cause them to trip each other … a real nuisance.

-- Gerry -- "I don't plan to ever really grow up ... I'm just going to learn how to act in public!"

View SKFrog16's profile

SKFrog16

661 posts in 2665 days


#2 posted 03-19-2010 06:19 PM

The Dane is right. I would also make sure you get 20 amp. GFCI’s. No wimpy 15 amp. Also make sure your outlets are 20 amp. rated.

-- Methods are many,Principles are few.Methods change often,Principles never do.

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Alan S

178 posts in 2782 days


#3 posted 03-19-2010 06:31 PM

If you want to use a single 10/3 cable for two independent GFCI circuits, I think you could manage to have only one 10/3 cable running from the panel to the pair of GFCI outlets, but downstream, each circuit would need its own 10/2 cable since GFCI compares hot current to ground current. Sharing a ground conductor between two GFCI circuits won’t work, I’m pretty sure. Check with your building code also. I’d say just put in two sets of 10/2 the whole way since you’re not going to gain much with 10/3.
Alan

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HokieMojo

2103 posts in 3193 days


#4 posted 03-19-2010 07:39 PM

Thanks for the input everyone.

Alan,
I think you are getting what I’m saying about not being able to just use a shared ground. I already ran 10/3 and it was NOT an easy job, maybe I’ll look for a 2 pole 20 amp GFCI circuit somewhere online since the big box stores don’t carry them. Either way, it’s kind of expensive getting GFCI protection on all 8 outlets (either by running 10/2 twice or 10/3 with repeated GFCI outlets). Just something I hadn’t fully accoutned for in my original budget.

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HokieMojo

2103 posts in 3193 days


#5 posted 03-19-2010 09:01 PM

I got my answers. I don’t like them but it seems I need to have GFCI outlets at every location. Ugh.

View Alan S's profile

Alan S

178 posts in 2782 days


#6 posted 03-19-2010 09:27 PM

Is the wiring daisy chained or is there a dedicated wire coming from the panel for EVERY outlet? If it’s daisy chained, like Dane said, you only need a GFCI outlet at the first location in the chain. You will only be able to get one 115v circuit instead of two like you probably hoped, but you don’t need 8 GFCI outlets.
Alan

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SKFrog16

661 posts in 2665 days


#7 posted 03-19-2010 09:45 PM

HokieMojo, take a ride to local electrical supplier. Tell him what you need, he will probably be able to help you out because they would know the code in your area and could even save you some money. Just explain what your doing.

-- Methods are many,Principles are few.Methods change often,Principles never do.

View WoodSparky's profile

WoodSparky

200 posts in 2567 days


#8 posted 03-19-2010 10:30 PM

Why 10/3?. 12/2 or 12/3 wold be adequate. Plus you will have a tough time trying to get #10 into the back of a GFI Receptacle. A two pole 20 or 30amp GFI breaker will set you back about a $100+. How about bring in the 10/3 into you 1st box were the 1st GFI would be located. leaving the box with 2 pairs of cable, one being feed off the load side of the 1st GFI and the 2nd being spliced off the B leg , with neutral pigtailed off the line neutral. The B leg cable would go to the 2nd GFI receptacle and so on.

-- So Many tools, So little time

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HokieMojo

2103 posts in 3193 days


#9 posted 03-19-2010 11:26 PM

the 10/3 is because the run from the box to the last outlet is about 100 ft. When I plug in a 100 ft extension cord (which I sometimes do for use in my garage) it just made sense to go up to the 10 gauge. I’ve also seen the trouble trying to get the wires to fit in the box. I bought extra deep boxes just to be safe though and that makes a big difference.

View TheDane's profile

TheDane

4997 posts in 3128 days


#10 posted 03-19-2010 11:53 PM

Just curious … have you considered running the 10/3 to a 30 amp sub-panel?

If your local code allows, the 10/3 could be used to feed a sub-panel and you could run your services from there.

-- Gerry -- "I don't plan to ever really grow up ... I'm just going to learn how to act in public!"

View HokieMojo's profile

HokieMojo

2103 posts in 3193 days


#11 posted 03-20-2010 12:02 AM

i do have a subpanel, but its a 100 amp sub. I’m not sure how that fixes the GFCI issue though.

edit: I see what you are seeing after thinking about it for a minute. I don’t think the sub would help because each pair of outlets is spread evenly along the 100 ft run. its ok, i think the multiple GFCI’s is the most practical, even if not the most cost efficient. thanks!

View TopamaxSurvivor's profile

TopamaxSurvivor

17671 posts in 3141 days


#12 posted 03-20-2010 01:58 AM

It’s either multiple GFIs or 2 conductor cables, no way around that!!

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

View hazbro's profile

hazbro

109 posts in 2455 days


#13 posted 03-20-2010 03:21 AM

since you’ve already run your 10/3, tie in to the first gfci outlet, and leave the extra wire abandoned in the romex. hook up regular receptacles with the remaining to wires and ground. just dead end the 3rd wire at the first outlet.

-- measure once, keep cuttin' til it fits

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TopamaxSurvivor

17671 posts in 3141 days


#14 posted 03-20-2010 07:07 AM

Splice some #12 pigtails on the 10 and it will be easier to put them in. #10 may break the GFCEI cases when you fight it into the box..

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

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