Outside Main breaker Panel

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Little Bill

Little Bill

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If you use an outdoor main breaker panel to feed an inside panel, (also main breaker) and use feed through lugs, do you have to treat the inside panel as a sub panel?
 
Little Bill said:
If you use an outdoor main breaker panel to feed an inside panel, (also main breaker) and use feed through lugs, do you have to treat the inside panel as a sub panel?
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Anything past the main disconnect gets a separate equipment grounding conductor. The feed thru lugs are on the load side of the breaker
 
Little Bill said:
So basically all the feed through lugs do is keep you from having to use a breaker on the bus to feed the other panel?
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basically and gives you the option of for example sending a full 200 amps on down the line to your sub rather than being limited to lets say 125 amp subfeed breaker on a residential panel im speaking. you can drop off a couple circuits from the main panel and still send the full size feed on down the line if you wish if there are extra spaces in the main panel buss of corse
 
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Feed through lugs

Feed through lugs

I would be concerned that the wire extending into the residential building would loose it's duel rating as the conductor supplying the total load of the building therefore requiring it to protected by a smaller breaker than the 200 amp main. Any other thoughts on this?
 
emfforhire said:
I would be concerned that the wire extending into the residential building would loose it's duel rating as the conductor supplying the total load of the building therefore requiring it to protected by a smaller breaker than the 200 amp main. Any other thoughts on this?
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It is not feeding the entire load of the building. If you use a smaller conductor then you must provide proper overcurrent protection for the conductor. If you want 200 amp capacity then you must use 200 amp conductors.

In the most common cases where 4/0 aluminum is commonly used nothing changes, unless the calculated load on the conductors is more than 180 amps. 4/0 is rated 180 amps and is allowed to be protected by next size higher device as long as the load is less than the 180 amp rating. For those who like to use copper for feeding dwellings you will have to increase to 3/0 or somehow lower the overcurrent protection to 175.
 
Little Bill said:
So basically all the feed through lugs do is keep you from having to use a breaker on the bus to feed the other panel?
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You can look at it a couple ways, the conductors connected to feed thru lugs are nothing more than an extension of the bus or the feeder starts at the lugs of the main breaker and includes the bus. Different, yet the same.
 
emfforhire said:
I would be concerned that the wire extending into the residential building would loose it's duel rating as the conductor supplying the total load of the building therefore requiring it to protected by a smaller breaker than the 200 amp main. Any other thoughts on this?
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It wouldn't really matter because the feeder conductors are not required to be larger than the service entrance conductors.
 
infinity said:
It wouldn't really matter because the feeder conductors are not required to be larger than the service entrance conductors.
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If we are talking about feeder conductors supplying motor loads maybe so but I kind of think he was inquiring about conductors sized according to 310.15(B)(7). If that is the case I think they must be sized to 310.15(B)(16) if they are not supplying the entire dwelling load - even if that means they are larger than the service conductors.
 
kwired said:
If we are talking about feeder conductors supplying motor loads maybe so but I kind of think he was inquiring about conductors sized according to 310.15(B)(7). If that is the case I think they must be sized to 310.15(B)(16) if they are not supplying the entire dwelling load - even if that means they are larger than the service conductors.
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actually you have a point there, never been called on that for feed thru panel and weve actually went with 310.15 (b(7) as in sending 2/0's down the line for 200 amps. Of course it's fine and no problems will occur but you just made me rethink this.
 
bobbymari said:
actually you have a point there, never been called on that for feed thru panel and weve actually went with 310.15 (b(7) as in sending 2/0's down the line for 200 amps. Of course it's fine and no problems will occur but you just made me rethink this.
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As worded, you can not hit a service panel with subfeed lugs that also has branch circuits or other feeders originating at that panel and then feed another panel off the subfeed lugs using 310.15(B)(7) sized conductors, because the feeder is no longer serving the entire dwelling. For the many that use 4/0 aluminum for 200 amps they get away with it without realizing that they need to size the conductor via a different code section because 4/0 AL can be protected by 200 amps as long as it is not loaded beyond its ampacity of 180.
 
kwired said:
As worded, you can not hit a service panel with subfeed lugs that also has branch circuits or other feeders originating at that panel and then feed another panel off the subfeed lugs using 310.15(B)(7) sized conductors, because the feeder is no longer serving the entire dwelling. For the many that use 4/0 aluminum for 200 amps they get away with it without realizing that they need to size the conductor via a different code section because 4/0 AL can be protected by 200 amps as long as it is not loaded beyond its ampacity of 180.
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agreed:thumbsup: the old "thats how weve done it in the past " , guilty as charged!
 
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