Lets see if I can explain this problem. There is a main distribution panel with 4 operating handles. They want to add another disconnect to feed another service in another section in the factory. They want to install a 3 pole 400 amp disconnect, then go to a Ct cabinet, then to an 800 amp main breaker panelboard. One problem is that the main distribution panel (MDP) is custom built and so they can't get a 3 pole 400 amp disconnect, but want to install 2- 200 amp 3 pole breakers and twin the service to the new CT cabinet. My first question to them would be that they needed a common tie handle to make sure that both breakers would trip out at the same time. Any other thoughts here?

Harold

Sounds as though you personally disapprove of their proposal, and I believe you should disapprove professionally as well. Maybe if they can't provide a common internal trip mechanism, they could provide interlocked shunt trip breakers. When they investigate the price of this they may be able to find a way to custom build mounting hardware for a 400 amp breaker. After all it is a custom built panel. Or tap the main buss for a 400 amp switch mounted beside the board if you approve.

Is there a listed handle tie manufactured for feeder-sized [three-pole?] circuit breakers?

Sounds like a violation to me, but an "A" for creativity.

Bob you are the man. The code reference eliminates my first suggestion, and gives Harold something to hang his hat on.

Bob has the correct answer but I just want to comment on "tie handles". The use of these devices does not create a common trip breaker especially on breakers of that size. All breakers are required to be "trip free", which means that even when the handle is held in the on position the breaker will still trip. If you tie larger breakers together, the one that sees the fault will open, but the handle tie to the second breaker will rarely cause the second breaker to open. Handle ties are intented to provide a means of common disconnect (manual), not common trip.
Don

OK, Let,s add some more info to this story. I was told that you can't get 400 amp 3 pole breakers for this panel anymore since it was a custom made panel. ( I wanted to see this backed up with a letter from the manufacture.) Would we accept a "Variation" to the code here and allow a custom made tie handle. Here in NJ we can allow "variations" if the AHJ feels that what is being offered is safe and hazard free. There is no UL listed tie handle as of yet, but that is why the contractor would try to get a custom made tie handle.

Iwire's reply covered this. It is a specific violation of the NEC and the custom made tie handle will not improve the situation enough to render the proposed installation safe. They are asking you to stick your neck out while they hand out machetes! Just say NO!
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Tom H

Harold:
AS Bob said, 240.8 is your NEC Article. As for a variation, I would not.

Now, that said, is the fact that they cannot MOUNT, or cannot obtain the 400 amp breaker??
Unless this is a real antique swbd......there is always a source for 'old' or obsolete breakers.

A little searching for the original mfg usually results in a 'find', or someone who took-over the 'custom brand'. All of the 'custom' gear I have seen uses well known mfg cb's, and 400 amp should not be that tough to locate.

Another concern is the AIC ratings of the gear, based on EXISTING conditions.

Do you have a mfg name of the gear???

Call me or e-mail...

John

John,

I believe the problem is that this board is a Square D custom made, main distribution panel that has room for about 6 breakers. The left side of the panel was created to accept large frame breakers, so there is three 3-pole large frame ( 400-600 amp) breakers on thihe left side. The right side of the panel can not accept the large frame style breakers. There is a smaller 3 pole 100 amp breaker there now and room for 2-3 more breakers. The EC said that he checked with the manufacture about getting a breaker for this panel and they said that there was no way to do it. (That is why I was looking for a letter from the manufacture stating that it was impossible.) He is going to get more information for me, the job is red tagged for now.

It sounds like you have a standard Square D I-Line distribution section. It may be in a custom enclosure but it is still standard busing.

The breaker arrangement you describe is an HCW type. The left hand side can accept any breaker up to their LC frame (600A trip) and the right hand side can accept a maximum KC frame (250A trip).

You should be able to mount (2) SL225 or (1) SL800 sub-feed lug kits on the right hand side of your panel (they look like breakers without handles). From these lugs you could run parallel conductors to an externally mounted 400A breaker.

[This message has been edited by JBD (edited 03-15-2004).]

The problem with a lug kit is that there is no space in the room for an enternal 400 breaker.
This service leaves the MDP and and the main electrical service room then proceeds more than 25 feet and into a different section of the warehouse. This is the reason for leaving the disconnect inside the existing MDP and not use an external breaker.

Harold
Tom could not have stated it any better. It is their pocketbook, and your neck.

Pierre

Harold, remembering I am not an inspector, I agree with Tom, John and Pierre.

If I was the AHJ there is no way I would stick my neck out on this.

The code is clear on this issue, no gray area, no exceptions etc.

It is not your problem to find a solution to this situation.

It is nice to have an inspector that wants to help, I can not say enough good things about inspectors that want to find a solution.

JMO, Bob

did you say 400amp feeding an 800amp mdp?

Thinking about this again... Why don't they tap off of the bus and add a service disconnect off of the existing switchgear?

Pierre