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Posted By: Clydesdale how many recepts on load of GFI? - 01/29/05 10:00 PM
today, i was talking with a coworker, and he said that you could only have a maximum of 3 recepticles on the load side of a GFI receptacle...this didn't sound right to me...this is in an office bulding in the kitchen area.
Not limmited by code. Some say manufacturers have limit. I have not seen any but I know it is not three.
Posted By: Clydesdale Re: how many recepts on load of GFI? - 01/30/05 01:13 AM
yeah it sounded like a load of crap to me..also...the structure is single story, wood framing. the same guy was saying that we weren't allowed to bore holes in the rafters and to lay the wires (12/2, 12/3)over the top of them. this also sounded like crap to me, but it was my first day, so I said:"ok, if that's how you want to run it fine with me." he said that the foreman(who i haven't met yet) didn't allow it...I was thinking that he didn't allow it because it took too long.

The whole thing is kind of sketchy, don't really know what to think yet.

also...the guy was saying that the boss didn't like 2 wires stapled stacked on top of each other, and to run them side-by-side on the 2x4...this also seems like a bunch of crap to me....

[This message has been edited by Clydesdale (edited 01-29-2005).]
Posted By: SolarPowered Re: how many recepts on load of GFI? - 01/30/05 01:40 AM
Out of curiosity, were the rafters dimensional lumber, or the bottom chords of trusses?
Posted By: Clydesdale Re: how many recepts on load of GFI? - 01/30/05 01:44 AM
I am not sure, there were metal plate connectors on them.
Posted By: Northbayec Re: how many recepts on load of GFI? - 01/30/05 01:59 AM
Drilling through rafters or trusses is not advisable in that it greatly reduces the structural integrity of the roof and the building. Many GCs and engineers won't allow it. As far as recepts on the load side of a GFI I was always taught no more than 4 on the load side due to more of a chance of nuisance tripping. The bosses request on the stacking of wires, well he is the one who signs the check. [Linked Image]

[This message has been edited by Northbayec (edited 01-29-2005).]
Posted By: Clydesdale Re: how many recepts on load of GFI? - 01/30/05 02:07 AM
just did a search about drilling trusses...doesn't look like the boss is going to be very happy when he sees the holes.

[This message has been edited by Clydesdale (edited 01-29-2005).]
Posted By: SolarPowered Re: how many recepts on load of GFI? - 01/30/05 06:16 AM
It sounds like you've already figured out what I was getting at...

It's OK to drill though normal rafters, but you really don't want to be drilling though trusses without permission and specific instructions from the engineer who designed them.

A normal rafter functions as a beam, which means that right in the center there's a dead area where there is very little stress. The top of the beam is in compression, the bottom in tension, and somewhere around the middle the force goes to zero. So it's OK to drill there, because it doesn't effect the strength of the beam.

A chord of a truss works differently. The whole chord is pretty much uniformly under compression or tension, depending on where it is in the truss. If you drill a 1" hole through a 2x4 chord, you've reduced it's strength by almost a third. That's a really bad thing.
Stappling the wires side by side on a 2X4 will not give you the proper clearance from the edge of the wood that is required. There is no reason to not put two cables under a staple.
Posted By: renosteinke Re: how many recepts on load of GFI? - 01/30/05 10:49 PM
I just sounds that the contractor is being conservative in his practices, and there's nothing wrong with that!

GFI's are listed to pass the entire load rating through them. I suppose that you then infer from other parts of the code that would mean 9 protected receptacles in commercial applications (assuming 15 amp circuit OR GFI).
In residential applications, while the NEC has no limit, many areas have local ordinances.

As others pointed out, you aren't allowed to drill "engineered trusses." That is, the pre-made things with metal plates ("gang nails") at the joints. Conventional rafters are another story.
SO the boss wants wires on top? Fine; but remember that you may also have to run boards alongside the romex to protect it.

Finally, most staples have never been evaluated, by UL or anyone else, for their use. Don't be surprised...you've been mounting stuff with "unlisted" nails, screws, and anchors forever!
The ones that ARE listed -usually intended for use in staplers- usually limit "stacking" to two cables. The NEC prohibition on stapling "on edge" might also be inferred to limit the heigth of a "stack" of cable.
Once again, there's nothing wrong with the boss being conservative. Far better than working for a hack!
Posted By: Sparks30 Re: how many recepts on load of GFI? - 01/31/05 01:19 AM
I ws alwas told not to drill the raters normal 2x10.
Posted By: Clydesdale Re: how many recepts on load of GFI? - 02/01/05 01:45 AM
yeah i was told by my teacher that the staples were not listed and that he even takes the insulation off the staple and stacks 3 wires under one staple(he is the state of Connecticut Electrical inspector so i guess he can do anything he wants anyway)
also, i was thinking it wouldn't give enough clearance(1.5 inches) from the edge of 2x4 if run side by side also...but i guess i'll just do what he says.
so if GFI's are rated for the full load, then do I just take 20A and divide by 1.5 and arrive at total number of receptacles for a 20A circuit (including the GFI itself)?
also...is the code the same for a kitchen in an office as it is in a dwelling unit? I tried looking it up but couldn't find anythingspecific to kitchens in office buldings.


[This message has been edited by Clydesdale (edited 01-31-2005).]

[This message has been edited by Clydesdale (edited 01-31-2005).]
Posted By: Wirenuttt Re: how many recepts on load of GFI? - 02/01/05 03:15 AM
I don't understand why the 3M SI-1 stakits aren't used more in situations like mentioned. It allows 4 cables and is designed to maintain the 1 1/4" rule clearance.
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