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big box calculations #15334
10/13/02 01:01 PM
10/13/02 01:01 PM
Eandrew  Offline OP
Joined: May 2002
Posts: 68
seattle, wa, usa
I just installed a 3x3 ct can (one on each side of a cinder block wall) with nipples going through the the wall.

This was done in order to avoid crossing pipes. Instead i just cross the wires inside the junction box.

But, my question has to do with the responsibility of box calculations. They seem quit complex in this situation.

I've got three 3" nipples going through the back of the box. On one side a 3 1/2 and a 2 1/2 and on the other side two 2 1/2 inches. On top of this, the forman wants to add 3 more 4" nipples going out the back for some more pipes and future use.

Would you take it upon yourself to go through all the angular calculations. And inquire about wires sizes in order to use table 312.6A.

I could see the jw being resposible for the diagonal dimension between k/o's (6xpipe size) since you have control over that. But when you are given a box , do you just assume it is sized within code, or not?

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Re: big box calculations #15335
10/15/02 10:28 PM
10/15/02 10:28 PM
The Watt Doctor  Offline
Joined: Dec 2001
Posts: 435
Mont Belvieu, TX
I'm not sure how to tackle your question. So, I'll start by throwing my experience at you, and my opinion as well. Hopefully someone can join in, and shed more light on the subject.
The times that I've installed "CT" cans, they were 30" X 42" because that is what the PoCo provided. They have rules on "where" the conduits can penetrate the can because they have to install their mounting hardware for the "CT's". So, "where" and "how many" conduits go in a "CT" can is up to your PoCo. You are at their mercy, unless the "CT's" are being used for something other than utility metering. A "CT" can is a cabinet, which you correctly pointed out in your post. No doubt about it Article 312 is where you should look.
The other box should be considered an Article 314.28 pull or junction box IMHO. The "off the cuff" rule for this is "V6, straight 8". Just the opposite of our normal thoughts about cars.
Eandrew, if you can give some more information, it will help. For now, my wife, The Watt Mama, is pestering me to get off the computer. I will post more later.

Get your motor runnin',

The Watt Doctor
Altura Cogen
Channelview, TX
Re: big box calculations #15336
10/21/02 12:25 AM
10/21/02 12:25 AM
Eandrew  Offline OP
Joined: May 2002
Posts: 68
seattle, wa, usa
v6, straight8, thats nice simple.

Yes, the CT i installed was only for transition purposes in running feeders. But thats good to know about the power companys own rules for CTS.

some day, when i start running work i'll really have to watch this. It could be a costly mistake. thanks for the response.


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