Subfeed Lugs

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jrohe

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Hey guys. I am working on training a few new employees and want to explain the difference between a set of subfeed lugs and a set of feed-through lugs. I've got a good example of a pair of panels where one section is fed through the feed-through lugs of another section. However, I am having problems finding a good photo of a pair of panels where one section is fed from subfeed lugs of another section. Would anyone happen to have a picture, with panel covers off, of this type of installation that they would be willing to share with me?
 
Do you mean a split buss panel

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I am not sure i understand your question. I don't think there is a difference. Are you reffering to a split bus?
 
Thanks so far; no I am not referring to a split bus panel. Feed-through lugs are located at the opposite end of the bus from a set of main lugs or main breaker like the photo in this thread.

I am looking for a panelboard setup that has a set of subfeed lugs, where the lugs are installed at the same end of the bus as the main breaker or main lugs. In a main breaker panelboard, the main breaker can be equipped with a dual set of lugs (one to feed the panelboard it is located in and another to feed another panel). In a main lug panel, it is usually just a set of stacked lugs.
 
jrohe said:
Thanks so far; no I am not referring to a split bus panel. Feed-through lugs are located at the opposite end of the bus from a set of main lugs or main breaker like the photo in this thread.

I am looking for a panelboard setup that has a set of subfeed lugs, where the lugs are installed at the same end of the bus as the main breaker or main lugs. In a main breaker panelboard, the main breaker can be equipped with a dual set of lugs (one to feed the panelboard it is located in and another to feed another panel). In a main lug panel, it is usually just a set of stacked lugs.
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I don't know if you find that as a out of the box configuration. I have swapped lugs for double feed don't know if was a listed configuration.
 
I don't believe I have ever seen a main breaker panel with lugs at the top to feed out. Perhaps as Sierra said you can change some of those lugs on the breaker to double lugs
 
Dennis Alwon said:
I don't believe I have ever seen a main breaker panel with lugs at the top to feed out. Perhaps as Sierra said you can change some of those lugs on the breaker to double lugs
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You have to spec your panelboards that way and it automatically adds about 20" of length to your tub. I just did a 480 volt 200 amp main panel with feed through lugs and the tub had to be 6' tall or better.
 
What about the type of subfeed lug kits that come as an accessory? For example, for Siemens loadcenters they have a 225A subfeed lug kit that snaps onto the buss and takes up 4 spaces under the deadfront.

I should be doing a quote for a customer tomorrow that has this setup with loadcenters side by side, and could take a pic or two when I remove the covers if it's something you could use.
 
Thank you to everyone for your responses! I am a huge fan of this forum - there is so much knowledge here! After talking to some switchgear reps, it does appear that the double lugs on the main breaker or the stacked lugs on the main lugs are a pretty rare animal and are usually added as an afterthought. I think I will avoid mentioning this arrangement for the time being.

Thanks again and Happy Thanksgiving!
 
jrohe said:
...it does appear that the double lugs on the main breaker or the stacked lugs on the main lugs are a pretty rare animal and are usually added as an afterthought.
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So, how does one accomplish such a feat? I looked and looked for some sort of double lug adapter that would allow me to install two sets of lugs on the existing non-removable breaker lug. Something like a Polaris PPT adapter is what I had in mind, but the PPT is for something else. Any such beast exist?
 
What I'm used to seeing are lugs that are designed to accept a single conductor OR two conductors like the ta-500-s from ilsco.
ImageUploadedByTapatalk1417006168.314612.jpg
I wish I had a picture with the covers off but this is what was used here to feed the 2 additional panels. The feeder comes into the left panel and used subfeed lugs like above to feed the middle panel. I added the right panel 2 years ago and the lugs in the middle panel were dual rated so it was a very easy installation
ImageUploadedByTapatalk1417006313.513999.jpg
 
Dennis Alwon said:
I don't believe I have ever seen a main breaker panel with lugs at the top to feed out. Perhaps as Sierra said you can change some of those lugs on the breaker to double lugs
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I have, but the main breaker was at the bottom of the panel in those instances - so still opposite end of bus from main breaker



jrohe, the important thing here is to know the difference between something tapped from the supply end of the main breaker and anything connected to the load side of the main breaker. Should this be a service supplied panel, anything tapped at or before the main breaker is still service conductors

Anything connected to the load side of the main breaker whether it be directly connected to the breaker, to a lug on the panel bus, or a plug on accessory that has no switch or overcurrent protection - is a feeder and the main breaker and that main breaker is the overcurrent protection device for that feeder.

If you don't have a "main breaker panel", but instead have a "main lugs only" panel with a sub feed lugs kit or option installed - NEC doesn't really see any difference between the lugs. You can run the supply to either set of lugs. Both sets of lugs need the same level of overcurrent protection. One exception may be a plug on sub feed lug kit. Say you use a 100 amp rated plug on sub feed lug kit on a bus protected by more then 100 amps overcurrent protection - you then have a feeder tap type of situation and will need overcurrent device within certain distance of the tap, but in those instances you need to ask why not just use the right breaker in the first place?

I am most familiar with Square D's NF and NQ panelboards with subfeed lug options. When you ask for subfeed lugs you get exactly same thing that is used as main lugs for a main lug only panel - just mounted on opposite end of the main breaker. If it is a main lug only panel and you add a subfeed lugs option - both ends of the bus are identical there really is no designated main or subfeed, the panel is supplied by a feeder and the feeder continues on through the panel bus and on to downstream feeder conductors.
 
kwired said:
I have, but the main breaker was at the bottom of the panel in those instances - so still opposite end of bus from main breaker



jrohe, the important thing here is to know the difference between something tapped from the supply end of the main breaker and anything connected to the load side of the main breaker. Should this be a service supplied panel, anything tapped at or before the main breaker is still service conductors

Anything connected to the load side of the main breaker whether it be directly connected to the breaker, to a lug on the panel bus, or a plug on accessory that has no switch or overcurrent protection - is a feeder and the main breaker and that main breaker is the overcurrent protection device for that feeder.

If you don't have a "main breaker panel", but instead have a "main lugs only" panel with a sub feed lugs kit or option installed - NEC doesn't really see any difference between the lugs. You can run the supply to either set of lugs. Both sets of lugs need the same level of overcurrent protection. One exception may be a plug on sub feed lug kit. Say you use a 100 amp rated plug on sub feed lug kit on a bus protected by more then 100 amps overcurrent protection - you then have a feeder tap type of situation and will need overcurrent device within certain distance of the tap, but in those instances you need to ask why not just use the right breaker in the first place?

I am most familiar with Square D's NF and NQ panelboards with subfeed lug options. When you ask for subfeed lugs you get exactly same thing that is used as main lugs for a main lug only panel - just mounted on opposite end of the main breaker. If it is a main lug only panel and you add a subfeed lugs option - both ends of the bus are identical there really is no designated main or subfeed, the panel is supplied by a feeder and the feeder continues on through the panel bus and on to downstream feeder conductors.
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Let me add to what I was saying here - if you have a multi-section panel that maybe has multiple columns with a "wire jumper" to supply one column bus section from the other column bus section, that is very likely a listed product as it is and the subfeed, feeders, taps are not part of the discussion of what is between those columns as far as NEC is concerned. The manufacturer may just call it part of the panel bus. If it is a part of a listed assembly, that wire jumper may not even be sized per NEC ampacity rules and it doesn't need to be, it was tested and listed as is.
 
Hey guys, thank you all so much for your feedback. The picture that was posted from Infinity is what I understand are feed-through lugs. Power comes in one side of the panelboard (the main breaker in the picture) and goes through the bus to a set of lugs; hence the term feed-through lugs. Feed-through lugs are what I see them called on shop drawings all of the time.

I am speaking strictly in terms of feeders. If you take Infinity's picture and move the feed-through lugs on the same end of the panelboard as the main breaker (like on the load side terminals of the breaker itself by equipping the main breaker with dual lugs), that is what I would call subfeed lugs. One set of lugs feeds the busbars in the panelboard the main breaker is located in while the other set of lugs is intended to feed another section via conductors that are the same size as the conductors on the line side of the breaker (thereby avoiding a feeder tap installation). This arrangement is necessary on occasion. For example, if there were an integral SPD at the bottom end of the panelboard.

As kwired pointed out, the subfeed lug kits that can be installed in a breaker space can result in a feeder tap and may actually take up more physical space than a breaker, so why not provide the breaker instead?

Again, it does sound like what I call the subfeed lugs where the outgoing lugs are installed at the same end f the panelboard as the incoming main is a rare animal and there may be better ways of accomplishing the installation. Thanks again for all of your responses!
 
jrohe said:
Hey guys, thank you all so much for your feedback. The picture that was posted from Infinity is what I understand are feed-through lugs. Power comes in one side of the panelboard (the main breaker in the picture) and goes through the bus to a set of lugs; hence the term feed-through lugs. Feed-through lugs are what I see them called on shop drawings all of the time.

I am speaking strictly in terms of feeders. If you take Infinity's picture and move the feed-through lugs on the same end of the panelboard as the main breaker (like on the load side terminals of the breaker itself by equipping the main breaker with dual lugs), that is what I would call subfeed lugs. One set of lugs feeds the busbars in the panelboard the main breaker is located in while the other set of lugs is intended to feed another section via conductors that are the same size as the conductors on the line side of the breaker (thereby avoiding a feeder tap installation). This arrangement is necessary on occasion. For example, if there were an integral SPD at the bottom end of the panelboard.

As kwired pointed out, the subfeed lug kits that can be installed in a breaker space can result in a feeder tap and may actually take up more physical space than a breaker, so why not provide the breaker instead?

Again, it does sound like what I call the subfeed lugs where the outgoing lugs are installed at the same end f the panelboard as the incoming main is a rare animal and there may be better ways of accomplishing the installation. Thanks again for all of your responses!
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IMO it doesn't really matter what you call it, or whether it connects right at the breaker, on the bus via a plug on lug kit, or at the end of bus opposite the breaker - the conductors landed in those lugs are still feeders protected at same overcurrent level as the bus. Should they be smaller conductors then the overcurrent protection then they are feeder taps and you need to make sure you follow applicable tap rules for your situation.
 
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