feed-through to subpanel?

[psoderlund]

I have a customer with a 200 Amp residential service. He wishes to add a 150 Amp subpanel in his walkout basement. The question is can the subpanel be fed by feed-through lugs in the main panel, the wire protected by a 150 Amp breaker in the subpanel? I have been unable to find a code reference for this situation.

 

[iwire]

Re: feed-through to subpanel?

The only way to do this would be to use a conductor rated for 200 amps.

That is unless the distance is under 25 feet, then you could use the tap rules.

 

[goldstar]

Re: feed-through to subpanel?

Psoderlund, could you please explain the proposed installation a little further ? Will the sub-panel be located adjacent to the main breaker panel or will it be remote from that location ?

Bob, after Psoderlund's reply could you please explain your response further also?

It is my understanding that if the sub-panel is added adjacent to the main breaker 200 amp panel and tapped off using feed-through lugs then it is not a sub-panel but part of the service equipment and the first part of Bob's answer is correct. If you decide to locate the new panel in a remote section of the basement you cannot run those service conductors "unfused" to that location. If you install a 150 amp main breaker in its own enclosure adjacent to the 200 amp main breaker panel you can then install a 150 amp main lug panel anywhere you want to.

Am I incorrect about this or not invisioning the installation correctly ?

Regards,

Phil

 

[psoderlund]

Re: feed-through to subpanel?

The main panel is located in a garage on the main level, and the subpanel in question will be located in the basement at least 50ft from the main panel. The main panel is a GE panel and since GE doesn't make a 150 Amp stab-in breaker I am somewhat at a loss.

 

[iwire]

Re: feed-through to subpanel?

Hi Phil, I made an assumption that the 200 amp service panel has a main breaker protecting it.

If that is the case there will be 200 amps available at the lugs he is coming off necessitating the use of 200 amp wire for the 50' foot run to the 150 amp panel.

If it was less than 25', going from memory he could use the 25' tap rule and use 150 amp wire between the 200 amp panel and the 150 main in the sub panel.

 

[psoderlund]

Re: feed-through to subpanel?

Bob, yes there is a 200 Amp Main breaker in the main panel, and there is a 150 amp main in the subpanel. I had assumed that since the panels will not be within site of each other that there needed to be a 150 amp breaker feeding the subpanel in the main panel, but I could use lugs in the subpanel. I have never heard of anyone using main lugs in the main panel to feed a smaller main breaker in a subpanel. This project would not have been a problem if GE made a 150 Amp breaker for the main panel, so I have been concidering replacing the main panel with a SquareD panel and reusing the old main as the subpanel in the basement, since I can get a 150 amp breaker for a SquareD panel.
Also, could you please provide me with code references? I would like to study this more, but I haven't been able to locate this stuff in the code book.
Thanks for all the help, I really do appreciate you guys taking the time to help me.

Thanks,
Peter

 

[tonyi]

Re: feed-through to subpanel?

Sounds like a cost compromise issue to me. If you take full capacity 200A wire to the sub, distance and tap rules won't matter - the sub could be either the 150A MBR or a 200A MLO (since the service main is still protecting that wire at 200A).

Since GE doesn't make the requisite breaker, there are other options - like a 150A disconnect next to the original panel. Then you can run 150A wire to the sub. Disadvantage: cost. Advantage, high amp disconnects are all located in the same place.

Q: is the 150A all needed in the same panel? Could a couple of cheaper/smaller 100's get the same effect? This might give you more flexibility in terms of locating the panels closer to the loads to be served, and the smaller wire is certainly easier to work with dusing installation.

 

[russ]

Re: feed-through to subpanel?

240.21 is the tap rule.

408.16 is overcurrent protection article for panel boards.

[ February 19, 2004, 06:45 PM: Message edited by: russ ]

 

[goldstar]

Re: feed-through to subpanel?

If that is the case there will be 200 amps available at the lugs he is coming off necessitating the use of 200 amp wire for the 50' foot run to the 150 amp panel.

If it was less than 25', going from memory he could use the 25' tap rule and use 150 amp wire between the 200 amp panel and the 150 main in the sub panel.

Bob,
Are you certain the tap rules apply here ? It sounds like Peter is probably going to run about 50' of SER cable from the feed-thru lugs ahead of the 200 amp main breaker (unfused) to a remote sub-panel. I still think he needs a 150 amp main breaker adjacent to the 200 amp main breaker panel.

I had assumed that since the panels will not be within site of each other that there needed to be a 150 amp breaker feeding the subpanel in the main panel, but I could use lugs in the subpanel.

Peter,
I went through this recently (it happened to be a Square D - QO panel) and I don't believe you can convert a (factory installed) main breaker panel to a main lug panel without voiding the UL listing

the sub could be either the 150A MBR or a 200A MLO (since the service main is still protecting that wire at 200A).

Tonyi,
From Peter's description it doesn't sound like the sub-panel will be protected by the 200 amp main breaker. If he's tapping off the feed thru lugs before the main breaker that 50' run is unprotected (the way I see it).

Since GE doesn't make the requisite breaker, there are other options - like a 150A disconnect next to the original panel. Then you can run 150A wire to the sub. Disadvantage: cost. Advantage, high amp disconnects are all located in the same place.

I think this is the best scenario.

 

[tonyi]

Re: feed-through to subpanel?

If indeed its a panel lacking genuine feed throughs and you wanted to tap ahead of the main, then that's a major issue.

Even tapping ahead of the mains to a seperate 150A disco would need a lot of care on the load calcs to ensure the service isn't going to be overloaded. I've seen this done a few times and it always gave me a bad feeling that some ill-considered additions of a few heavy draw units later on were going to cause a service overload.

Unless its a real antique GE I would imagine GE might have a replacement guts kit available to fit that enclosure with some real feedthrough lugs.

 

[goldstar]

Re: feed-through to subpanel?

Tonyi & Bob,

Maybe it's me and I'm not familiar with the same feed-thru lugs you're talking about. What I'm familiar with are feed-thru lugs that are on top of a main breaker that allow you to feed-thru to another main breaker panel in close proximity. If there are kits that tap onto the buss-bar after the 200 amp main breaker then maybe both of you are correct and I'm offering some incorrect advice. If there are any photos or maybe a link available for those devices could you post them here so we can all benefit from them.

Thanks,
Phil

 

[steve66]

Re: feed-through to subpanel?

Goldstar: Square D makes subfeed lugs that attach to the line side of a MLO bus, and they make feed-thru lugs that attach to the other end of the bus. See:
Square D PN107

Does GE make a 100A stab-in breaker? Your customer may want to consider if a 100A panel in the basement would be sufficent. Then you add a 100A breaker in the existing panel and run 100A wire to a 100A MLO panel in the basement. This would be much cheaper than running 200A wire to a 150A MCB panel.


Steve

 

[psoderlund]

Re: feed-through to subpanel?

The Main panel does not have feed-through lugs, I was planning to use a lug kit GE makes to add lugs on the load side of the 200 Amp main breaker.
The reason he needs a 150Amp subpanel is that he wants to outfit the 1750 sqft basement with a full kitchen, two bedrooms, sump pump, living room, and add a hot tub outside. So far my load calc justifies the 150Amp sub. Unfortunately, he will not have much room for expansion on the 200Amp main service, but he isn't overloaded yet.

thanks,
Peter

 

[iwire]

Re: feed-through to subpanel?

Peter

Two options that I can think of if you need the 150 amps.

1)Use the feed through lugs you spoke of and feed a 200 amp fused switch at the panel with 150 amp wire using the tap rules put in 150 amp fuses and run 150 amp conductors to a 150 amp MLO subpanel.

2)Use the feed through lugs and run 200 amp conductors to a 200 amp MLO subpanel.

If you are stuck using 200 amp conductors I do not see much savings in a 150 amp panel.

Phil I am not sure what you are asking about the tap rule I was thinking of, if you are more specific I will be happy to answer.

Bob

 

[tonyi]

Re: feed-through to subpanel?

Steve, yea there is a 2-pole THQL 100A breaker (THQL21100), and even a 2-pole 125A (THQL21125). I've actually seen both of these, and used some of the 21100's. Some Big Orange I wandered through one day had one of the 125's in stock.

I found some vague references to a THQL21150 in some used breaker dealer place when searching around, but couldn't find anything specific. GE's site search seemed virtually worthless in turning up actual product numbers.

 

[ccha9219]

Re: feed-through to subpanel?

I agree with tonyi
ite and ge both make a 2 pole 125
if that amp rating wont meet your needs put in a 200 amp mlo
ccha9219

 

[horizon]

Re: feed-through to subpanel?

I've used Square D Homeline breakers in the place of the GE in the past; usually less expensive. They are avaiable up to 200 amps.
Wouldn't that help in this application?

 

[hurk27]

Re: feed-through to subpanel?

ccha9219 And horizon

You can not use a breaker from another manufacture unless it is a UL clasifide type breaker and is UL listed for that panel.
Cuttler Hammer does make a few, But they must have the panel in there list of panels it can be installed into.

This is against NEC artical 110.3(B)

 

[stars13bars2]

Re: feed-through to subpanel?

Psoderlund
Does the planned load require a 150amp subpanel? If so have you done a load calculation on the existing residence and come out with 50 amps or less?

 

[iwire]

Re: feed-through to subpanel?

Stars that is a good question.

I think we can assume if the total load was calculated it would exceed 200 amps.

Would it really exceed 200 amps?