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Trough sizing... #57990
10/24/05 09:23 PM
10/24/05 09:23 PM
Attic Rat  Offline OP
Member
Joined: Dec 2003
Posts: 524
Bergen Co.,N.J. USA
... 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"
Work Gear for Electricians and the Trades
Re: Trough sizing... #57991
10/25/05 12:18 AM
10/25/05 12:18 AM
Attic Rat  Offline OP
Member
Joined: Dec 2003
Posts: 524
Bergen Co.,N.J. USA
[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"
Re: Trough sizing... #57992
10/25/05 04:50 AM
10/25/05 04:50 AM
I
iwire  Offline
Moderator
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
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
Re: Trough sizing... #57993
10/25/05 07:47 AM
10/25/05 07:47 AM
Attic Rat  Offline OP
Member
Joined: Dec 2003
Posts: 524
Bergen Co.,N.J. USA
... 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"
Re: Trough sizing... #57994
10/25/05 08:03 AM
10/25/05 08:03 AM
I
iwire  Offline
Moderator
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
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
Re: Trough sizing... #57995
10/25/05 08:07 AM
10/25/05 08:07 AM
R
Ryan_J  Offline
Moderator
Joined: Aug 2003
Posts: 1,374
West Jordan, Utah, USA
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
Re: Trough sizing... #57996
10/25/05 08:24 AM
10/25/05 08:24 AM
I
iwire  Offline
Moderator
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
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
Re: Trough sizing... #57997
10/25/05 08:34 AM
10/25/05 08:34 AM
R
Ryan_J  Offline
Moderator
Joined: Aug 2003
Posts: 1,374
West Jordan, Utah, USA
I didn't see that he was splicing.

Are you splicing, AR?


Ryan Jackson,
Salt Lake City
Re: Trough sizing... #57998
10/25/05 08:40 AM
10/25/05 08:40 AM
I
iwire  Offline
Moderator
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
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
Re: Trough sizing... #57999
10/25/05 08:42 AM
10/25/05 08:42 AM
I
iwire  Offline
Moderator
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
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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