Securing Cables in Sub Panel

[mikeyd]

I am adding a sub panel for an addition on my house. The Code check book recommended by my inspector says,
"Cables must be secured to the panel with clamps used in accordance with their listing. Some clamps will accept two small cables; a bundle through one clamp is a common defect"
I checked the existing main panel on my house and all the cables are routed through one large hole. I would like to pass inspection the first time. My question is:
How do I determine what size and how many cables I can put through a certain size clamp? I have the typical 3/4" and 1" clamps that are passed through a hole in the panel and secured with a nut.

On a second note. Is it permissable to hold two cables to a stud with one metal staple?

 

[charlie]

Re: Securing Cables in Sub Panel

This forum is for:
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<font size="2" face="Verdana, Helvetica, sans-serif"> From the way you are asking the question, you should not be doing this work.

A listing is the way a NRTL has tested a device, clamp, piece or equipment, or assembly. In other words, you have to follow all the instructions that come with the items as well as the listing agency's instructions.

You are also required to follow the NEC with the modifications that were done in your local area or state.

 

[pierre]

Re: Securing Cables in Sub Panel

The question I have for Homeowners is, what do you think you might be saving by doing the 'more' complicated electrical work in your own house? I know that pride in doing a 'project' at the house is great, I do that also. But... the long term effect of a mistake in this application might not be realized for some time. The fact that you mention that all the cables are routed through one big hole in the main panel leads an experienced person in the field to say HMMMM!
It is great that you are motivated to do work in your own home, but the only suggestion I would make to an inexperienced person not in the trade on this forum is to hire a PRO!
Good Luck!

Pierre

[ July 04, 2003, 09:25 AM: Message edited by: pierre ]

 

[mikeyd]

Re: Securing Cables in Sub Panel

Thank you for the replies. As for my experience, I teach Industrial Technology (Shop) in electronics and automotives. I have a masters degree in Industrial technology. I am owner/contractor for a 1684 square foot addition to my home. My question specifically requests how to figure how many and what size conductors can pass through a certain size clamp. The clamps did not come with any "instructions" as to the the size and number of conductors.

In referance to my comment of all of the cables passing through one big hole in the main panel, This is the main panel that was installed on the house when I bought it new in 1990. The code check book I am using says that this is a defect so either it was installed improperly by the "Pro" or the code must have changed in the last 13 years.

In addition, I have seen many examples of securing more than one piecee of romex to a stud with one metal staple, and I am curious if this is allowable by code.

If anyone has an answer to the questions posed, I would greatly appreciate hearing about it.
Thank you.

 

[jxofaltrds]

Re: Securing Cables in Sub Panel

I'll try to keep this simple.

Go to any electrical supply and look at the back of a box of c-500's or c-750's.


these are the two you will most likely use. This way you will have the manf. specs.

Two nm under ine staple. Make sure your staples at the sub panel are with-in 12" of the connector entering the box.

We sometimes hate to answer questions that seem simple to us.

Make sure you understand the grounding/bonding issues at the sub panel. You can search this site for sub panel questions.

Mike P.

 

[iwire]

Re: Securing Cables in Sub Panel

Originally posted by mikeyd:
I checked the existing main panel on my house and all the cables are routed through one large hole. ......... My question is:
How do I determine what size and how many cables I can put through a certain size clamp?

312.5(C) is the article for this, and according to the handbook commentary.

Individual cable clamps or connectors are required to be used with only one cable per clamp or connector, unless the clamp or connector is identified for more than a single cable.

I have never seen a connector rated for more than 2 cables.

The 3/4" and 1" ones you have are for larger size cables, not for multiple 12 or 14 AWG cables.

 

[a.wayne3@verizon.net]

Re: Securing Cables in Sub Panel

Iwire if I am not mistaken,,,,1/2 in.nm connectors
are rated for 2 12/2,3/4-4 12/2,and 1 in.-6 12/2.This came to bear when we started the 99 code and prior to that we used a 2 1/2 pvc m.a
with a bushing and all nm cables were routed into the panel thru that.I want to say Raco was the manufacturer,and we contacted them and recieved these #s as the ratings for them.There were additional ratings for multiple 6/2,10/2
10/3 in 1 in connectors.....I`ll check when i get back to the office Monday.To all have a safe and happy 4th of July

 

[iwire]

Re: Securing Cables in Sub Panel

a.wayne I would be interested to have that info. Here in MA I have never seen that done, not to say that you can not.

Any panels here that I have seen have one or two cables per connector, that could be just a local preference.

Thanks and take it easy.

Bob

 

[tom baker]

Re: Securing Cables in Sub Panel

Along with Charlies post, one of the concerns I have is "what else is not being asked"? I know from 25 years of electrical expericence that even with a permit and inspection, the inspector can't check every aspect of the installation.

 

[mikeyd]

Re: Securing Cables in Sub Panel

Again thank you for your responses. I had to search for a manufacturer that listed specs on the cable ranges. Arlington Industries lists 1/2" connectors as rated for 1 cable 14/2 to 10/2, 14/3 to 10/3 and 2 cables 14/2 to 12/2. 3/4" connectors rated for 1 cable 8/2 to 6/2, 8/3 to 6/3 or 8/2 to 4/2 SE

 

[karl riley]

Re: Securing Cables in Sub Panel

About running a whole bunch of conductors through one big hole (I saw it in public housing in Detroit), the Code says you can only do this with panels surface mounted on the wall, not with flush panels. There are specs for how to do it, with a conduit protecting them, etc. If you need the Code reference, I could look it up, but I spent some time verifying this at one time.
Karl

 

[karl riley]

Re: Securing Cables in Sub Panel

About how many NM cables can be run through a clamp in a cabinet, I am curious, since 2002 312.5(c) just says "each cable shall be secured to the cabinet." What does that mean? One cable per clamp? There is nothing about what the cabinet manufacturer specs allow.

The handbook author has an opinion, but is it Code?

There is a ruling on boxes no larger than 2 1/4" by 4", that 2 NMs can share an opening. Why wouldn't it say that for cabinets if that were the case?
Karl

 

[iwire]

Re: Securing Cables in Sub Panel

312.5(C)Exception

Is the one that allows multiple NMs to enter a sufacemount panel through 18" to 10' of raceway.

 

[mikeyd]

Re: Securing Cables in Sub Panel

I have a 30/40 flush mount sub panel mounted between 2x6 studs on 16" centers. This eliminates access though the sides. Mounting the panel through the back to 2x6 cross braces eliminates rear access. This leaves 30 KO's top and bottom to supply a max of 40 circuits. The manufacturer (Siemens) obviously intended to run more than one nm through each KO. Additionally the specs on the 1/2" clamps permit 2 cables (14/2 or 12/2).

 

[gwz2]

Re: Securing Cables in Sub Panel

Also, multiwire branch circuits are permitted, thus for a 1? 120/240V system, it would be possible to only need 20 KO's for a 40 circuit panelboard.

Seems as though everyone wants to circumvent what the CODE permits with a method that is not permitted.