# Feeding 200 amp sub from 400 amp



## B-Nabs (Jun 4, 2014)

Probably a 3 pole 200A breaker for that panel is not available.


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## B-Nabs (Jun 4, 2014)

Yep just looked up that panel type, max branch breaker available is 100A.


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## telsa (May 22, 2015)

Look at the bussing.

You're going to have to replace the guts.

It may be far more practical to set (2) 100A daughter panels.


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## s4nsp4rky (Jan 12, 2017)

That's what I told the manager but the design engineer won't agree. 

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## cl2sparky (Jan 3, 2017)

s4nsp4rky said:


> That's what I told the manager but the design engineer won't agree.
> 
> Sent from my SAMSUNG-SM-N910A using Tapatalk


Engineers are idiots!!!
JMHO


Sent from my 1911-A1


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## sbrn33 (Mar 15, 2007)

I really don't understand the problem? Are you designing this or is someone else?


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## backstay (Feb 3, 2011)

s4nsp4rky said:


> hello everyone
> 
> I got a situation at a job site. So I came here to hopefully find an answer for this. I got a 400 amp 120/208 3 phase main lugs only panel. I need to feed a 200 sub from this. I have asked 5 different supply houses and seems like it's not possible. Electrical engineer and project manager said they do this often. I'm not sure what I'm missing here.
> 
> ...


If they do it often, why are they asking you how?


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## s4nsp4rky (Jan 12, 2017)

backstay said:


> If they do it often, why are they asking you how?


He spec jobs like this often and he never had a electrician complaining that's what he meant.


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## s4nsp4rky (Jan 12, 2017)

sbrn33 said:


> I really don't understand the problem? Are you designing this or is someone else?


I'm the electrician suppose to do this installation. I just got the specs. 

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## telsa (May 22, 2015)

100A 3-pole is your tap limit with this bussing. Period.

You are limited by the conductivity of aluminum and the surface-contact area given the dimensions of the C/Bs where they meet the bus.

If it had been ordered -- years back when -- with pass through lugs at the bottom -- you'd be good to go. The panel can is certainly dimensioned to permit such schemes.

However, once the design was committed, there is no field kit available to make the bussing 'grow.'

C-H will have to sell you a wholly new set of guts -- with the magic pass-thru lugs at the bottom. You'll pay dearly, of course.

Twinned 100A panels is THE obvious solution. 

One could imagine some tortured scheme that uses twinned 100A C/Bs to feed a 200A daughter breaker -- in parallel. You'd be using the tap-rules and equal-length conductors. You might get away with some combiner blocks -- so often used these days in PV schemes.

This would all be to no proper purpose -- a total waste of time and materials -- to craft a pretty dodgy scheme. ( Painful to look at. )


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## ponyboy (Nov 18, 2012)

Did you already check to see if there's a feed through lug kit for that panelboard? Start with that. If it doesn't you might have to see about intercepting the feeder and splitting it before the panelboard. Feed through kits are available for most interiors but you usually need a bigger tub than normal to accommodate it so even if you can get a kit your tub is probably too small. 


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## Maple_Syrup25 (Nov 20, 2012)

ponyboy said:


> Did you already check to see if there's a feed through lug kit for that panelboard? Start with that. If it doesn't you might have to see about intercepting the feeder and splitting it before the panelboard. Feed through kits are available for most interiors but you usually need a bigger tub than normal to accommodate it so even if you can get a kit your tub is probably too small.
> 
> 
> Sent from my iPhone using Tapatalk




If he put in a splitter in would he have to install a main breaker in the existing 400a panel? Obviously would need protection in the 200a panel


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## ponyboy (Nov 18, 2012)

Maple_Syrup25 said:


> If he put in a splitter in would he have to install a main breaker in the existing 400a panel? Obviously would need protection in the 200a panel
> 
> 
> Sent from my iPhone using Tapatalk




I'm assuming the 400 is a sub and already has an ocpd feeding it. If he intercepted the feeder he would need to follow the tap rules of 240.21(B)(1) through (B)(5). 


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## Cow (Jan 16, 2008)

If we were doing that, I'd be looking for replacement lugs for the top of the panel. If you can find 3-4 hole lugs to replace those 2 hole lugs, you can tap off the line side following the tap rules and set a 200A fused disconnect next to the panel. Then run as far as you need to, to reach your 200 amp subpanel.

This is just one method.


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## s4nsp4rky (Jan 12, 2017)

Cow said:


> If we were doing that, I'd be looking for replacement lugs for the top of the panel. If you can find 3-4 hole lugs to replace those 2 hole lugs, you can tap off the line side following the tap rules and set a 200A fused disconnect next to the panel. Then run as far as you need to, to reach your 200 amp subpanel.
> 
> This is just one method.


Can it be done by using a 200 amp panel with a main circuit breaker?


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## LGLS (Nov 10, 2007)

s4nsp4rky said:


> Can it be done by using a 200 amp panel with a main circuit breaker?


The 200a panel at your goal is irrelevant. It could have a main or not. The 200a disconnect at your 400a panel tap will protect the feeders and the 200a panel.


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## wildleg (Apr 12, 2009)

I hope I don't sound like debbie downer, but this is a normal situation with normal solutions. Tap/feed/bug/tap rule/whatever.

You need to do one of two things, depending on the job constraints:

1) if the engineer is designing, or has designed the job, let him do his job and provide you with the plans/sketches/specs you need to do the job. If he can't do his job, suggest to whomever is in charge, that you can, for a fee, have the job engineered by someone else with a positive and effective result. On the other hand, if the engineer is just being a prick and adamantly maintains that the existing design will work, you need to cut him down to size by sending a short and politely worded RFI, copied to the owners/client, that explains the problem. Something like "Existing 400A panel x does not have the capacity to supply the 200A subpanels y and z as shown in page n. See attached "Exhibit A" with specs of existing and proposed panels. This issue is currently holding up portions of our work, and effect on the schedule is unknown at this time, but may result in unforeseen delays, as well as additional costs. Please advise asap as to how you would like us to proceed. "

2) if somehow you have gotten stuck redesigning this portion of the job (how did that happen?), then post the one-line diagram here and maybe the group can give you a solution (there are some things missing).

hope this helps


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## Spark Master (Jul 3, 2012)

How about feeding 2) 100amp subs?

Is 100amp breaker the largest available in that frame size ?


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## Tonedeaf (Nov 26, 2012)

http://www.eaton.com/Eaton/Products...n/Panelboards/Lighting/PRL1a/index.htm#tabs-2

this is the link to this panel board. Look under documentation. There is options for both feed thru breakers and feed thru lugs for this type of panel. I cannot tell from the pic, but that can looks big enough, if the bus bars are long enough ( I think you need 3 bus bar mounting holes) you can install either.

I would call the local EATON rep. directly and ask for the proper part number.


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## sbrn33 (Mar 15, 2007)

Tonedeaf said:


> http://www.eaton.com/Eaton/Products...n/Panelboards/Lighting/PRL1a/index.htm#tabs-2
> 
> this is the link to this panel board. Look under documentation. There is options for both feed thru breakers and feed thru lugs for this type of panel. I cannot tell from the pic, but that can looks big enough, if the bus bars are long enough ( I think you need 3 bus bar mounting holes) you can install either.
> 
> I would call the local EATON rep. directly and ask for the proper part number.


I agree but if there is an EE involved I would make him do it just to prove a point.


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## triden (Jun 13, 2012)

sbrn33 said:


> I agree but if there is an EE involved I would make him do it just to prove a point.


A Canadian EE wouldn't do that as it's usually left to the EC to figure out how to go about it. Might be different in the states.


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## brian john (Mar 11, 2007)

1. Different style line side lugs and a 200 Amp MCB panel within 10' or 25' if you can comply with the tap rules.

2. I THINK this panel is designed for top bottom feed, so you can mount lugs on the bottom for a tap I THINK, without a full picture of the panel I can not be 100-% positive.


When you take a picture give all the information REMOVE ALL COVERS.


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## mgraw (Jan 14, 2011)

EATON's catalogue shows that panel is/was available with 225 amp sub feed lugs or breaker. I would check with EATON.


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## TRurak (Apr 10, 2016)

Use the tap rule on the 400 amp feeders .....


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## foothillselectrical (Mar 17, 2013)

s4nsp4rky said:


> That's what I told the manager but the design engineer won't agree.
> 
> Sent from my SAMSUNG-SM-N910A using Tapatalk


Just tell the design engineer to provide you with breaker specs...


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## Southeast Power (Jan 18, 2009)

s4nsp4rky said:


> hello everyone
> 
> I got a situation at a job site. So I came here to hopefully find an answer for this. I got a 400 amp 120/208 3 phase main lugs only panel. I need to feed a 200 sub from this. I have asked 5 different supply houses and seems like it's not possible. Electrical engineer and project manager said they do this often. I'm not sure what I'm missing here.
> 
> ...


Interesting that its a 42 circuit panel with only 17 circuits used and that its a problem.
What are they trying to accomplish? 
They can only get 100 amp sub-panels out of it.
That's about it. 
or
Install a 200 amp panel and feed it with a 100 amp breaker. Bam! 200 amp panel!


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## TRurak (Apr 10, 2016)

Here's a pic of what I've used in you situation in the past. These are insulation piercing taps. The ones in the pic might be the wrong side for you.


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## TRurak (Apr 10, 2016)

Sorry for the typos. I'm on a smartphone and I can't figure out how to edit my posts.


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## Southeast Power (Jan 18, 2009)

brian john said:


> 1. Different style line side lugs and a 200 Amp MCB panel within 10' or 25' if you can comply with the tap rules.
> 
> 2. I THINK this panel is designed for top bottom feed, so you can mount lugs on the bottom for a tap I THINK, without a full picture of the panel I can not be 100-% positive.
> 
> ...


Interesting that the most important part of those guts are covered up.


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## Southeast Power (Jan 18, 2009)

TRurak said:


> Here's a pic of what I've used in you situation in the past. These are insulation piercing taps. The ones in the pic might be the wrong side for you.


That would be a bit over complicated using on parallel conductors. If they don't have some exposed bus bar hanging out of the bottom ready for lugs, I would look more towards Brian's suggestion of changing the line lugs out. Those cant be more than 4/0.


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## Going_Commando (Oct 1, 2011)

I'd get stacked quad lugs to replace the dual lugs on the feeds. Nipple a 200A fused disco or enclosed breaker to the panel enclosure, hop off the new stacked feed lugs at the top of the panel to feed the new 200A disconnect, then hop out of your 200A disconnect to your new sub panel.

Tap rule, baby.


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## electric_mayhem (Apr 27, 2012)

I had to do something similar recently...I was able to remove the bottom six breakers, tap the bus and install a fusible disco next to the panel...Un-engineered project and client had a 3 phase 150 amp piece of equipment. I am not sure if the sub feed lug kit is 100% kosher in that 400a panel but sometimes options are limited. Good luck


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