# 250mcm feeding 100 amp panel?



## backstay (Feb 3, 2011)

Electrocuter said:


> I am currently taking part in the rewiring of a trailer park. We are planning on feeding 100 amp panels from a main 400 amp panel. However, due to the distances involved and after voltage drop is taken into consideration we are dealing with 250mcm aluminum. The problem is fitting this huge wire under the mains of the 100 amp panels.
> 
> When talking about this with the local inspector, we were advised that it would be acceptable to crimp #3 conductor to the 250 Mcm to accommodate the 100 breaker. It seem somewhat pointless to me to reduce the wire size like this. Does anyone have any similar experiences??


We do this all the time. That short #3 will not effect voltage drop at all.


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## backstay (Feb 3, 2011)

I figure you must be at 450 feet to need 250 AL


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## Electrocuter (Jul 3, 2012)

backstay said:


> We do this all the time. That short #3 will not effect voltage drop at all.


Even if both ends of the 250 are reduced??


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## Electrocuter (Jul 3, 2012)

backstay said:


> I figure you must be at 450 feet to need 250 AL


Yes, 450+


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## backstay (Feb 3, 2011)

Electrocuter said:


> Even if both ends of the 250 are reduced??


Yes, both ends.


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## Bbsound (Dec 16, 2011)

Voltage drop is dependent on resistance. 
What's the difference in 10' of #3 from a breaker in a big panel or 10' of #3 from a Polaris connector with 250 feed?

Nothing.


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## backstay (Feb 3, 2011)

You're not restricting flow with the #3. You're decreasing resistance with the 250.


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## Electrocuter (Jul 3, 2012)

Bbsound said:


> Voltage drop is dependent on resistance.
> What's the difference in 10' of #3 from a breaker in a big panel or 10' of #3 from a Polaris connector with 250 feed?
> 
> Nothing.


Right. That makes sense! Thanks


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## Electrocuter (Jul 3, 2012)

backstay said:


> You're not restricting flow with the #3. You're decreasing resistance with the 250.


Put even better!


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## RePhase277 (Feb 5, 2008)

I would use crimp on reducing pins instead.


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## Electrocuter (Jul 3, 2012)

backstay said:


> You're not restricting flow with the #3. You're decreasing resistance with the 250.


Where are you from? Or what code do you follow is a better question, and do you know off hand what the rules for that are other the 3 m rule?

In the CEC it mentions mechanical protection..?


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## Electrocuter (Jul 3, 2012)

InPhase277 said:


> I would use crimp on reducing pins instead.


Hm sounds interesting. Never heard of em! I'll have to check the supplier. Thanks!


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## thoenew (Jan 17, 2012)

Try fitting 4/0 under a lug in a 30A disconnect.


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## Zparme (Nov 11, 2010)

Will you have to install a pull box before the panel, or can you make the crimps inside the 100 amp panel?


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## Electrocuter (Jul 3, 2012)

Zparme said:


> Will you have to install a pull box before the panel, or can you make the crimps inside the 100 amp panel?


It's all underground. We're running teck, to and from outdoor weather proof panel enclosures with a tub to enclose crimps.


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## backstay (Feb 3, 2011)

Electrocuter said:


> Where are you from? Or what code do you follow is a better question, and do you know off hand what the rules for that are other the 3 m rule?
> 
> In the CEC it mentions mechanical protection..?


Minnesota, 2011 NEC


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## 123electric (Jun 3, 2012)

They make wire reducer luggs specificity designed for what you are doing without modifieing your equipment or cutting off strands on your wire


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## jstrick2 (Jun 29, 2012)

This happens all of the time. Especially when an engineer/designer gets a little nutty with ductbank derates or you have some "fun" preference to get DC to that area way out behind the woodshed. I know because I have sadly done it a few times in the past.

Its always fun to see an electrican standing there with a 350MCM next to a DCS cabinet.

-Term/pullbox
-Reducing pins
-In-line splice kit or similar when you cannot reduce pin it down far enough


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## sbrn33 (Mar 15, 2007)

InPhase277 said:


> I would use crimp on reducing pins instead.


Try bending 4/0 in a 100 amp enclosure. Not fun. Set a tap box or reduce it underground with shrink sleeve.


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## kaboler (Dec 1, 2010)

I've only went to 1 trailer park, but it seems to me that the feeders are run underground to posts that pop up next to each trailer, and then from there, fed to the panels inside the trailer. So why not reduce at the posts?


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## thoenew (Jan 17, 2012)

Had three different sets of 1/0 that need to go under 30A disconnects this morning. We just went into junction boxes, then to the disconnect.


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