Terminals

[KasseemF]

I am a relatively new electrical inspector. I would like to know what the code says in relation to having more than one service conductor on a terminal. Like for example I inspected a building that hade a three-phase 350 amp main breaker that has two terminals for terminating the conductor on each phase, but the electrician placed three conductors and had two on a single terminal. Where in the code approves or disapproves this?

Also he had 3 - 3/0 AWG conductors for each phase this 350A. would this be severely overating the conductor in relation to the main breaker or is it because the cable is above the rating of the breaker it is okay?

 

[Dennis Alwon]

but the electrician placed three conductors and had two on a single terminal. Where in the code approves or disapproves this?

If the lug is listed for 2 terminals then it is compliant. Even the grounded conductor is allowed to have 2 terminals under one lug if it is parallel conductors and approved for use. Art. 408.41.

 

[KasseemF]

Re. terminals

Re. terminals

Well I understand that from Art. 110.14. but i see two screews .. which I assume should be for two conductors on on each phase of the breaker .. should the elctrician be allowed to place a third conductor on each phase allowing one of those screws to have two conductors?

 

[iwire]

I have never seen a terminal on a large breaker that was rated for more then one conductor per 'screw'.

Some larger lugs used on neutral bars are specifically listed for two conductors per screw but they are the rarity not the norm.

 

[Dennis Alwon]

I have never seen a terminal on a large breaker that was rated for more then one conductor per 'screw'.

Some larger lugs used on neutral bars are specifically listed for two conductors per screw but they are the rarity not the norm.

I have seen a breaker on a 400 amp panelboard (just yesterday inf act) that had a factory install parallel feeders in the lug of the breaker feeding the busbar. Normally I see a breaker tied directly to the buss but this one had 2 conductors under each screw. I do believe it came from the factory that way. It certainly looked like it.

 

[iwire]

I do believe it came from the factory that way. It certainly looked like it.

Which means for better or worse they can jam as many as they want under the terminal. :smile:

 

[hardworkingstiff]

I have seen a breaker on a 400 amp panelboard...

I installed a 400-amp 1-phase MB panel and I told the supplier I was going to run two wires per phase so make sure the MB would take 2-conductors per phase. When we went to wire it, there was only one 'screw' per phase. It took a while, but we found the lug was listed for 2-conductors. Surprised me.

 

[teco]

Most of the breaker lugs or disconnect switch lugs I see that are rated for two conductors have the normal wire hole with a kinda half circle notched into the front of the wire hole. When I ask cutler hammer directly they told me it means its a single lug rated for more than one wire. I have never seen a parallel lug thats rated for more wires than the amount of wire holes given.

 

[r_merc]

Keyhole

Keyhole

There are lugs that are rated for more than one wire per screw. They tend to have the shape of a keyhole (Circle with a half moon on top). Usually the rating is stamped on the side or tongue of the lug.

Rick

 

[brian john]

Square D makes a termination lug for more than one conductor, not sure of the frame size involved but the Allen set is lousy too shallow strips easily.

 

[weressl]

I have seen a breaker on a 400 amp panelboard (just yesterday inf act) that had a factory install parallel feeders in the lug of the breaker feeding the busbar. Normally I see a breaker tied directly to the buss but this one had 2 conductors under each screw. I do believe it came from the factory that way. It certainly looked like it.

Yep,

That does not mean that the lugs were approved for two - or more -conductors. Just because it came from the factory that way does not mean it is right.

 

[Dennis Alwon]

Yep,

That does not mean that the lugs were approved for two - or more -conductors. Just because it came from the factory that way does not mean it is right.

Agreed but others have said there are lugs that exist which are suitable for 2 wires. My point was perhaps they did exist. It would also appear that if the unit were UL listed then the terminals would have to be approved for 2 terminals. Perhaps I am mistaken.

 

[weressl]

Agreed but others have said there are lugs that exist which are suitable for 2 wires. My point was perhaps they did exist. It would also appear that if the unit were UL listed then the terminals would have to be approved for 2 terminals. Perhaps I am mistaken.

I agree. Unfortunately UL listing does not mean much anymore. With the qualified workers forced out with retirement you will find replacements who receive very little training as what the listing all encompasses and violate it inadvertently.

 

[iwire]

It would also appear that if the unit were UL listed then the terminals would have to be approved for 2 terminals.

No.

Equipment manufacturers are not bound by 110.3(B) they can, and often do 'misuse' terminals.

Look inside almost any HVAC equipment and you will often find a terminals listed for one say 3 AWG and it has four 12 AWGs in it.

The listing of the particular lug is of no importance as the entire unit will be listed as a whole.

 

[eprice]

KasseemF,

As you can see from the discussion, two conductors in one lug is ok if the lug is listed for two, but most large lugs are not listed that way. If you cannot find confirmation that the lug in question is so listed on the lug, have the electritian provide documentation of the listing.

I'm not sure that I understand your second question. You did not say whether these are copper or aluminum conductors, but even if aluminum, the ampacity of a 3/0 conductor at 75 degrees is 155 amps. Three paralleled conductors would have an ampacity of 465 amps.

 

[weressl]

No.

Equipment manufacturers are not bound by 110.3(B) they can, and often do 'misuse' terminals.

Look inside almost any HVAC equipment and you will often find a terminals listed for one say 3 AWG and it has four 12 AWGs in it.

The listing of the particular lug is of no importance as the entire unit will be listed as a whole.

So you are saying that UL would stamp the lug as recognized component for single conductor use, then they would stamp a panel as UL approved where one of the component installation violates their own criteria of 'recognized component'?

I would think that the recognized component remains within it listing parameters if the installation description is followed.

 

[iwire]

So you are saying that UL would stamp the lug as recognized component for single conductor use, then they would stamp a panel as UL approved where one of the component installation violates their own criteria of 'recognized component'?

Yes, absolutely.

The listing is for us knuckle dragger's in the field where our work will not be tested and listed as a whole.

 

[weressl]

Yes, absolutely.

Weel do you care to verify this with UL or do you want me to do it?