# Why do GFCI outlets have 4 lead and 4 load holes?



## 1655graff (Jul 27, 2007)

I've bought 2 different brands of GFCI outlets. Both have the holes in the back for 2 lead cables (2 black and 2 white wires) coming in and 2 load cables (2 black and 2 white wires). Why?:huh:

Especially since the instructions tell you NOT hook up more than 6 wires total which would be 1 black/1 white lead; 1 black/1 white load and 2 ground wires, correct?:jester:


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## dSilanskas (Mar 23, 2008)

1655graff said:


> I've bought 2 different brands of GFCI outlets. Both have the holes in the back for 2 lead cables (2 black and 2 white wires) coming in and 2 load cables (2 black and 2 white wires). Why?:huh:
> 
> Especially since the instructions tell you NOT hook up more than 6 wires total which would be 1 black/1 white lead; 1 black/1 white load and 2 ground wires, correct?:jester:


They have that many holes because you can wire a GFCI different ways. And you only can put one ground wire on a GFCI or any device for that matter. You splice the grounds and leave one long to attach to the GFCI.


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## Bigplanz (Apr 10, 2009)

I dpn't know the answer to this question. However, I would like to know why they have to be so big. They won't hardly fit in a regular handybox, and retro fitting an old (circa 1950) box in the bathroom with a GFCI is a b**th.

Surely, in this age of micro electronics, they could make a GFCI small enough to fit in a box.:yes:


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## clintb (Mar 13, 2009)

Bigplanz said:


> I dpn't know the answer to this question. However, I would like to know why they have to be so big. They won't hardly fit in a regular handybox, and retro fitting an old (circa 1950) box in the bathroom with a GFCI is a b**th.
> 
> Surely, in this age of micro electronics, they could make a GFCI small enough to fit in a box.:yes:


I read about a rather innovative approach on contractortalk.com (shh, I'm not in the trades, but still like to read their stuff.) where the sparky used stranded pigtails for everything inside the box. It does add extra expense, but how much of a pain is it to shove 12ga into a box? That's not even factoring how difficult it is to keep the outlet or switch nice and straight. With stranded pigtails, no problem. I'll be going this route when I redo the electrical in my downstairs.


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## darren (Nov 25, 2005)

clintb said:


> I read about a rather innovative approach on contractortalk.com (shh, I'm not in the trades, but still like to read their stuff.) where the sparky used stranded pigtails for everything inside the box. It does add extra expense, but how much of a pain is it to shove 12ga into a box? That's not even factoring how difficult it is to keep the outlet or switch nice and straight. With stranded pigtails, no problem. I'll be going this route when I redo the electrical in my downstairs.


That is hard to beleive, to me that would be a waste of time. Useing #12 and shoveing in a box is not as bad as people put it out to be. Prebend the wire and it should shove in there nicely, once the plug or switch is in you can move it around to get it to sit nice.


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## 1655graff (Jul 27, 2007)

dSilanskas said:


> They have that many holes because you can wire a GFCI different ways. And you only can put one ground wire on a GFCI or any device for that matter. You splice the grounds and leave one long to attach to the GFCI.


So one can load a GFCI with 2 separate runs (going downstream of it)? 
- Will it work?
- and it is "kosher" per the national electrical code?

And when would one need/use 2 separate lead runs into a GFCI?


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## Maureentoo (Apr 14, 2009)

1655graff said:


> So one can load a GFCI with 2 separate runs (going downstream of it)?
> - Will it work?
> - and it is "kosher" per the national electrical code?
> 
> And when would one need/use 2 separate lead runs into a GFCI?


If you want the outlets downstream to be protected by the GFCI then run off the load to the next outlet. If you don't want the outlets downstream protected then run off the line to the next outlet. That's why there are 4 holes in the GFCI.


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## 1655graff (Jul 27, 2007)

Maureentoo said:


> If you want the outlets downstream to be protected by the GFCI then run off the load to the next outlet. If you don't want the outlets downstream protected then run off the line to the next outlet. That's why there are 4 holes in the GFCI.


OK, Thank you. Ahhhh... so that explains the 2 sets of lead holes. That totally makes sense now. WOW!

BUT so you can run 2 separate runs off the load of the GFCI, correct? And if so, then I guess I still don't understand the Instruction sheets which say not to hook up more than 6 wires total. If you run 2 separate runs off the load, won't you be connecting 7 (2 lead; 4 load; and 1 pig tailed ground). 

Sorry for being such a newbie/dummy:jester:


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## rgsgww (Jul 5, 2008)

1655graff said:


> BUT so you can run 2 separate runs off the load of the GFCI, correct?


Yes



1655graff said:


> And if so, then I guess I still don't understand the Instruction sheets which say not to hook up more than 6 wires total.


Exclude the ground (attach it though!)
Look at it like this. Hot and neutral to line holes. Two hots and two neutrals for the load side. 6 wires.

What is this gfci going to serve?


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## williswires (Jul 21, 2008)

What brand/model # of GFCI are you using?

I will look up the instruction sheet for it, but it probably means not including the ground.

In the one instruction sheet I looked at, it said that if you have more than 4 wires to contact an electrician. Maybe this is because the mfg. wants to make sure the homeowner doesn't do something wrong, I don't know.


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## jerryh3 (Dec 10, 2007)

williswires said:


> What brand/model # of GFCI are you using?
> 
> I will look up the instruction sheet for it, but it probably means not including the ground.
> 
> In the one instruction sheet I looked at, it said that if you have more than 4 wires to contact an electrician. Maybe this is because the mfg. wants to make sure the homeowner doesn't do something wrong, I don't know.


If you have more than four wires at the box there could be a possibility that is a multi-wire branch circuit. They can be a little tricky to wire if you're unfamiliar with them.


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## 1655graff (Jul 27, 2007)

williswires said:


> What brand/model # of GFCI are you using?
> 
> I will look up the instruction sheet for it, but it probably means not including the ground.
> 
> In the one instruction sheet I looked at, it said that if you have more than 4 wires to contact an electrician. Maybe this is because the mfg. wants to make sure the homeowner doesn't do something wrong, I don't know.


Yes, I think that's the Cooper Instruction sheet. The other is Levitron. So I bought them at Lowes and HD. I don't have the instructions in front of me at this moment since I'm away from the house.

Someone (yes, I know that's a dangerous omen) told me that pig-tails are used for more than one set of load, but then I bought these outlets and saw the 2 sets of load wire holes on both of them, and got to wondering if I could use both sets of holes on the load side. If I can, then that seems simple enough to me.


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## rgsgww (Jul 5, 2008)

Do you have red and black wires in this box?


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## PaliBob (Jun 11, 2008)

Bigplanz said:


> I dpn't know the answer to this question. However, I would like to know why they have to be so big.


 GFCI's are actually much smaller than originally even though they now have an 8 pin SMD (Surface Mount Device) IC
http://www.national.com/ds/LM/LM1851.pdf

The early GFI's (The name GFCI came later) were way too big to fit in any Handy box so the ones I first came in contact with in the early 70's were panel mounts made by AirPax.

After National came out with their LM1851 (only in the DIP package- SMD came later) the GFI's were first able to be packaged in a Double D style package. Picture a really FAT old style receptacle (before Decora), only these early GFI's only had a *Single* outlet. The other space was taken up by the Test/Reset buttons.

Anybody here remember those? I had a few stll around but I threw them all out ten years ago thinking I'd never have any use for those relics.

I am still surprised that modern packaging is able to get all the GFCI circuity crammed in such a small package. When you look at the enclosed block schematic at the block labeled Solid-State Circuitry there is much more in that block than the IC. There are a number of discrete components including a DC power supply for the IC.

Note also that there is no connection between ground and the GFCI circuit. The GFCI does not need a ground to do its job. Note the GFCI internal test button connects the bleed resistor to the CT input whereas the Test button on a three prong GFCI tester connects a bleed resistor between AC and Ground.

EDIT 2 Corrected error on schematic


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## thefamouscbc (Apr 20, 2009)

clintb said:


> I read about a rather innovative approach on contractortalk.com (shh, I'm not in the trades, but still like to read their stuff.) where the sparky used stranded pigtails for everything inside the box. It does add extra expense, but how much of a pain is it to shove 12ga into a box? That's not even factoring how difficult it is to keep the outlet or switch nice and straight. With stranded pigtails, no problem. I'll be going this route when I redo the electrical in my downstairs.


OMG I hate being called a sparky!!!


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