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?
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.
Sounds like a violation to me, but an "A" for creativity.
240.8 Fuses or Circuit Breakers in Parallel. Fuses and circuit breakers shall be permitted to be connected in parallel where they are factory assembled in parallel and listed as a unit. Individual fuses, circuit breakers, or combinations thereof shall not otherwise be connected in parallel.
Bob Badger Construction & Maintenance Electrician Massachusetts
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! -- Tom H
"This alternating current stuff is just a fad. It is much too dangerous for general use" Thomas Alva Edison
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.
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.