Multiple wires on each lug of a panelboard main breaker?

[Toolteck]

Installing a 400 amp 3 phase panelboard with a main breaker supplied by an overhead busway. Is it a code violation to run two 3/0 cables to each lug on the panelboard main breaker instead of running a 600 kcmil cable to each lug. It would be much easier to hand bend the smaller wires into position in the busway switch and in the panelboard. 110-14 (a) says "Terminals for more than one conductor and terminals used to connect aluminum shall be so identified."

 

[Cow]

It is a violation to use a lug in any other way than the manufacturer intended you to use it. So if the lug you're looking at doesn't say (2)1/0-250mcm or similar then it is not designed to take two wires. Lugs made to take two cables usually have teardrop or egg shaped holes.

Most modern breakers I come across have all the different lug specs right on the front of the breaker that are available as optional replacements.

 

[augie47]

Agree 100% with Post #2

Just to cover all bases, keep in mind that if you elect to parallel 3/0s in ONE conduit in lieu of 600kcmil your derated ampacity will be at least 15% lower than the ampacity of the 600.

 

[Toolteck]

Thanks guys for your input!

 

[kwired]

I think you will find most terminations for 400 thru 600 amps and maybe even 800 amps will quite often be rated for a single or two conductors in same "port" of the termination.

 

[iwire]

I think you will find most terminations for 400 thru 600 amps and maybe even 800 amps will quite often be rated for a single or two conductors in same "port" of the termination.

That is not my experience.

 

[Carultch]

Installing a 400 amp 3 phase panelboard with a main breaker supplied by an overhead busway. Is it a code violation to run two 3/0 cables to each lug on the panelboard main breaker instead of running a 600 kcmil cable to each lug. It would be much easier to hand bend the smaller wires into position in the busway switch and in the panelboard. 110-14 (a) says "Terminals for more than one conductor and terminals used to connect aluminum shall be so identified."

Terminals are by default, only rated for one wire. Unless listed and marked otherwise.

Most lugs in excess of 400A, are listed and marked otherwise. It is common that there is a small wire range for two wires up thru "the aughts", and a large wire range up to the big KCMIL sizes.

You may also see a "snowman" shaped lug, and these are usually rated for two wires.

 

[iwire]

Most lugs in excess of 400A, are listed and marked otherwise. It is common that there is a small wire range for two wires up thru "the aughts", and a large wire range up to the big KCMIL sizes.

You may also see a "snowman" shaped lug, and these are usually rated for two wires.

Can you point me to a single barrel lug that is not a 'snowman' but is listed for more than one conductor?

I am not running into any other than small grounding bars.

 

[Carultch]

Can you point me to a single barrel lug that is not a 'snowman' but is listed for more than one conductor?

I am not running into any other than small grounding bars.

I saw the LA300 main breaker on a Square D panel that is rated for parallel wires up to 250 kcmil. It isn't a snowman shape or a standard circle, but the lug interior looks like a rounded rectangle.

 

[jim dungar]

I saw the LA300 main breaker on a Square D panel that is rated for parallel wires up to 250 kcmil. It isn't a snowman shape or a standard circle, but the lug interior looks like a rounded rectangle.

And they have used some 'teardrop' lugs, which are almost but not quite snowmen.

 

[kwired]

That is not my experience.

I suppose it can vary depending on what brands of equipment you commonly see, nds what lines within those brands you see most often, or even if you are not the person ordering/specifying when there is a choice of factory installed termination equipment. Also supply house stock items have any options already chosen when they order stock.

 

[petersonra]

most larger MCCB have a variety of terminal options that can be supplied by the manufacturer.

I know some people claim that only manufacturer supplied lugs can be used on breakers, but IMO a listed (as opposed to recognized) connector could also be used, although the mechanical configuration of some breakers sometimes precludes doing so.

Some breakers have a tongue type terminal that can be ordered in lieu of lugs specifically so you can use what ever connectors you want to bolt to the tongue.

 

[iwire]

most larger MCCB have a variety of terminal options that can be supplied by the manufacturer.

I know some people claim that only manufacturer supplied lugs can be used on breakers, but IMO a listed (as opposed to recognized) connector could also be used, although the mechanical configuration of some breakers sometimes precludes doing so.

Some breakers have a tongue type terminal that can be ordered in lieu of lugs specifically so you can use what ever connectors you want to bolt to the tongue.

Personally I think any proper fitting lug will do.

The problem is that the manufactures instructions will direct us to use 'part number 87655' and some inspectors will point to 110.3(B).

Redoing work is much to costly than just ordering factory lugs in the first place.

 

[Carultch]

I think you will find most terminations for 400 thru 600 amps and maybe even 800 amps will quite often be rated for a single or two conductors in same "port" of the termination.

An interesting issue I've encountered, is whether you can connect non-identical wires to the same port of a two-wire rated lug.

As an example, a 400A disconnect feeding a 200A panel and a 150A panel each with a main breaker. Connect 1/0 for the 150A panel, and 3/0 for the 200A panel. Obviously both conductors have to be the same metal (can't mix Cu and Al in the same port). But can they be dissimilar sizes?

 

[jim dungar]

Personally I think any proper fitting lug will do.

Almost always, the UL Listing for the breaker in that panel includes any protrusion of the lug into the 'wire bending space at terminations' requirements, so styles with tangs are rarely used. Other lugs may have issues with clearances, the finger safe barrier may no longer perform its function, or the set screws may come too close to the deadfront.

I know some Square D I-line style breakers have different acceptable lugs than the same breakers in 'lug-lug' versions.

 

[sandsnow]

Can you point me to a single barrel lug that is not a 'snowman' but is listed for more than one conductor?

I am not running into any other than small grounding bars.

Aside from the grounding bars, two wires in a round hole is always a red flag.

I too would like to know if that unicorn exists.

I have seen listed equipment with two wires in a round hole done that way by the manufacturer. Certain blah blah UL testing makes it ok.

I always wondered why Ilsco for example didn't jump on that and get more lugs rated for two wires

 

[kwired]

Almost always, the UL Listing for the breaker in that panel includes any protrusion of the lug into the 'wire bending space at terminations' requirements, so styles with tangs are rarely used. Other lugs may have issues with clearances, the finger safe barrier may no longer perform its function, or the set screws may come too close to the deadfront.

I know some Square D I-line style breakers have different acceptable lugs than the same breakers in 'lug-lug' versions.

That is likely only because of wire bending space or other outside factors, otherwise for I line breakers the plug on jaws are the only thing that makes them "I-Line", Otherwise a type FA, LA, etc. is the same thing as a "lug-lug" version on the "lug" end, and any accessories that do fit the "lug-lug" breaker will fit the same series in an I-Line. The accessory may not be limited by the fact it is an I line breaker as much as it maybe is limited by the specific panelboard or cabinet it is used with.

I have seen some similarities in other manufacturers products at times though Square D is what I have most familiarity with.

I know you are probably aware of this just wanted to expand a little on what you said for anyone that may not know.

 

[kwired]

An interesting issue I've encountered, is whether you can connect non-identical wires to the same port of a two-wire rated lug.

As an example, a 400A disconnect feeding a 200A panel and a 150A panel each with a main breaker. Connect 1/0 for the 150A panel, and 3/0 for the 200A panel. Obviously both conductors have to be the same metal (can't mix Cu and Al in the same port). But can they be dissimilar sizes?

Not sure if there is a general rule for this or not. When I have run into such a situation the distance was usually short and was no big deal to use the larger size conductor for both loads.

 

[sandsnow]

An interesting issue I've encountered, is whether you can connect non-identical wires to the same port of a two-wire rated lug.

As an example, a 400A disconnect feeding a 200A panel and a 150A panel each with a main breaker. Connect 1/0 for the 150A panel, and 3/0 for the 200A panel. Obviously both conductors have to be the same metal (can't mix Cu and Al in the same port). But can they be dissimilar sizes?

For some reason I always thought same size, but UL doesn't back me up on that. I think the manufacturer would have the answer. Sorry about the big image, I'm working from my kindle.
Quote from category code ZMVV:
Multiple conductors ? Connectors generally accommodate a single conductor under a clamping mechanism unless otherwise identified, such as with the number of conductors located parenthetically in front of the wire size or range. Some connectors may have a single-conductor wire range as well as a second multiple-conductor wire range. Some connectors, such as twist-on connectors, will have multiple conductors expressed in a list of wire combinations.

 

[readydave8]

I always wondered why Ilsco for example didn't jump on that and get more lugs rated for two wires

Because they would then sell fewer lugs