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#57990 10/24/05 09:23 PM
Joined: Dec 2003
Posts: 524
Member
... I'm trying to size an indoor trough for the 300 amp service we're working on... I'd be coming into the top of the trough with a 3" pipe,and exiting through the bottom of the trough into (2)150 amp panels via (2)-2" nipples... My recollection is that since this will be a straight pull,I must go with 8 times the largest diameter pipe,which will give me a minimum of 24".. the other dimension large enough to accomodate lock-nuts...will a 24"X 8"X 8" trough be adequate?? my supply conductors will be 250kcmil copper..also I must bond this trough,as I'm using PVC nipples..what size bonding wire should I go with??
Russ


.."if it ain't fixed,don't break it...call a Licensed Electrician"
#57991 10/25/05 12:18 AM
Joined: Dec 2003
Posts: 524
Member
[Linked Image]


(edited to put image on the ECN server)

[This message has been edited by electure (edited 10-26-2005).]


.."if it ain't fixed,don't break it...call a Licensed Electrician"
#57992 10/25/05 04:50 AM
Joined: Jan 2003
Posts: 4,391
I
Moderator
Nice signal balloon. [Linked Image]

I am having a hard time picturing your installation.

Are you planing on the trough being vertical or horizontal?

If you are planing on 8" x 8" being enough space to get two 3" raceways in I think that will be difficult. I would go 10" x 10".

Can you describe it a little more.


Bob Badger
Construction & Maintenance Electrician
Massachusetts
#57993 10/25/05 07:47 AM
Joined: Dec 2003
Posts: 524
Member
... The trough would be horizontal,with one 3" pipe entering through the "top" and two 2" pipes coming out the "bottom",each going into a 150 amp. CB panel, a typical service installation in a basement for a 300 amp service..
Russ

[This message has been edited by Attic Rat (edited 10-25-2005).]


.."if it ain't fixed,don't break it...call a Licensed Electrician"
#57994 10/25/05 08:03 AM
Joined: Jan 2003
Posts: 4,391
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Moderator
Then it will have to be larger between the top and the bottom.

First it sounds to me like the angle pull rules apply as it sounds like the 3" will not line up with the 2 - 2" and I imagine you are splicing in the trough.

Quote
314.28(A)(2) Angle or U Pulls. Where splices or where angle or U pulls are made, the distance between each raceway entry inside the box and the opposite wall of the box shall not be less than six times the metric designator (trade size) of the largest raceway in a row. This distance shall be increased for additional entries by the amount of the sum of the diameters of all other raceway entries in the same row on the same wall of the box. Each row shall be calculated individually, and the single row that provides the maximum distance shall be used.

3" x 6 = 18"

or

2" x 6 + 2" = 12"

So the you need 18" minimum between the incoming 3" and the out going two - 2"


Bob Badger
Construction & Maintenance Electrician
Massachusetts
#57995 10/25/05 08:07 AM
Joined: Aug 2003
Posts: 1,374
R
Moderator
I don't think there is a cut and dried code answer to this, because the code doesn't define what a straight pull is and what an angle pull is.

Bob, I agree with your take, in calling this an angle pull, but I think that 376.23(B) applies only to the distance between the raceways. 376.23(A) applies to the physical size of the wireway, which would permit a very small wireway, if the raceways have enough space between them.

I have a change submitted to the 2008 to this section to try to clarify this (I would like to see a 30 degree deflection govern the rules).

[This message has been edited by Ryan_J (edited 10-25-2005).]


Ryan Jackson,
Salt Lake City
#57996 10/25/05 08:24 AM
Joined: Jan 2003
Posts: 4,391
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Moderator
You lost me Ryan, if it has splices it is an angle pull that is cut and dry.

Also 376.23(B) only applies to raceways containing the same conductors. Assuming he is splicing 376.23(B) is not applicable.

Bob


Bob Badger
Construction & Maintenance Electrician
Massachusetts
#57997 10/25/05 08:34 AM
Joined: Aug 2003
Posts: 1,374
R
Moderator
I didn't see that he was splicing.

Are you splicing, AR?


Ryan Jackson,
Salt Lake City
#57998 10/25/05 08:40 AM
Joined: Jan 2003
Posts: 4,391
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Moderator
He has one 3" incoming and two 2" outgoing.

My money is on a splice in the trough.

He may have run parallels in the same 3" but I doubt it as than you have derating issues.

My view is biased as I almost never run parallels for less than a 400 amp circuit. [Linked Image]


Bob Badger
Construction & Maintenance Electrician
Massachusetts
#57999 10/25/05 08:42 AM
Joined: Jan 2003
Posts: 4,391
I
Moderator
Of course I am just a Hack so don't listen to me. [Linked Image] [Linked Image]


Bob Badger
Construction & Maintenance Electrician
Massachusetts
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