GerryB
Senior Member
- Location
- woodbridge, ct. USA
I have a customer with a 400 amp service and two 200 amp panels. I want to install an interlock on each panel and parallel the two breakers. Any code or safety issue? I don't see one.
Interlock kits in parallel
- Thread starter GerryB
- Start date
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Strathead
Senior Member
- Location
- Ocala, Florida, USA
- Occupation
- Electrician/Estimator/Project Manager/Superintendent
I don't understand your terminology. an interlock? parallel what "the breakers". Also for time sake, where are the panels located in relation to a.) the service b.) outside.
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
in lieu of a transfer switch there are kits made to add a backfed breaker to a panelboard that has a mechanical interlock with the main breaker so only one can be on at a time. the generator feeds power into the PB through the backfed breaker. they are not really in parallel which would be a code violation.
off hand I can't think of a reason it would be unsafe or could not be made code compliant. but, I did not think about it all that much.
- Location
- Massachusetts
I agree with Bob.
GerryB
Senior Member
- Location
- woodbridge, ct. USA
The interlock kit is a sliding type bracket that mounts on the panel cover. The back feed breaker is installed on two slots below the main breaker, the side being determined by the brand of panel. In the normal position the main is on, the back feed breaker is off. The back feed breaker is wired to a power inlet box where the generator will be plugged in. The back feed breaker can not be turned on without turning off the main and sliding the bracket up, which is what you would do when you need to use the generator which now feeds the panel through the back fed breaker with no danger of going out to the street. I have done quite a few, some of which an inspector has seen, and there has been no problem. In this case there are two panels so I want to put an interlock on each panel and a wire from each back feed breaker to a j-box, then from the j-box to the power inlet box. When they run the generator they can now energize both panels. (it is actually set up like that now except they have no interlock or transfer switch and he wants it to be code compliant)
ceb58
Senior Member
- Location
- Raeford, NC
Sounds good. You will be correcting a violation and possibly saving the HO from injuring, or worse , a lineman in an outage.
kwired
Electron manager
- Location
- NE Nebraska
Each panel in your case needs proper transfer equipment - which such kits as you describe are an option.
Unless each "main" in your case has both sets of line side conductors connected together and both sets of load side conductors connected together you have nothing in parallel. You possibly could have just the line side connected in parallel, but if load side is also connected in parallel you likely have other code issues if there is more then a single operating handle for these devices if they are in parallel.
Unless each "main" in your case has both sets of line side conductors connected together and both sets of load side conductors connected together you have nothing in parallel. You possibly could have just the line side connected in parallel, but if load side is also connected in parallel you likely have other code issues if there is more then a single operating handle for these devices if they are in parallel.
Strathead
Senior Member
- Location
- Ocala, Florida, USA
- Occupation
- Electrician/Estimator/Project Manager/Superintendent
I know about those. Generally called a Kirk key. I don't see an application where you have two 200 A panels fed from 400 A. So I assume he must have been using that term for a different meaning.
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
different from a kirk key.
http://natramelec.com/?gclid=Cj0KEQ...Q4oNZlOS2yvD3AjYHpHvNWOPH87FWLQr0MaApnF8P8HAQ
kwired
Electron manager
- Location
- NE Nebraska
Some have questioned whether you can use third party devices like those in your link, but you are starting to find more similar devices being made by the panel OEM's these days. But they typically only make them for current production panels and not for retired model numbers, those you still have to find in a third party product most of the time.
Strathead
Senior Member
- Location
- Ocala, Florida, USA
- Occupation
- Electrician/Estimator/Project Manager/Superintendent
Bob! I am fully aware of most of the options available for most interlocking applications, as well as many situations that warrant them. That doesn't even start to answer my question! The OP has a 400 amp service. He has two 200 amp panels. He wants to install and interlock on EACH ONE, and parallel the to breakers. First thing, I am not aware of an interlock like you drew that will interlock the breakers in two separate panels, however the Kirk key will which is why I went there first. Second If I have a 400A service and I run a 3/0 to a 200A panel with a main breaker before or where it enters the building. And then I do the same with another. What am I using interlocks for? I see no mention of generators. I see no mention of loads larger than the service feeder. I see absolutely no use for interlocks. As such, I question if the OP was either not giving us all the information, or using terminology incorrect, or I, in my stupidity am missing the elephant in the room!
- Occupation
- Licensed Electrician
The OP wants to feed two panels with one generator. The "transfer switches" is manual. The generator and the wires don't have to match the service.
- Location
- Massachusetts
There is no reason both interlocks must operate together.
The can safely transfer either or both panels at any time.
The can safely transfer either or both panels at any time.
Strathead
Senior Member
- Location
- Ocala, Florida, USA
- Occupation
- Electrician/Estimator/Project Manager/Superintendent
Dave and Bob. I see the error of my ways now. I didn't get notified of Gerry's answer to my question and so I was never up to speed on his clarification. Now I have egg on my face and I am fully versed in the conversation. :ashamed1:
qcroanoke
Sometimes I don't know if I'm the boxer or the bag
- Location
- Roanoke, VA.
- Occupation
- Sorta retired........
I actually have done this.
2-200 amp Sq D HOM panels each with its own interlock.
Really had to think about it and convince myself that it would work.
GerryB
Senior Member
- Location
- woodbridge, ct. USA
I had to think it through also. The only danger with these interlocks is if someone leaves the cover off the panel, thinks all the breakers should be on and turns on the generator breaker. Now you have live prongs at the power inlet box. Now in our case with two panels let's see, leave one cover off, turn on generator breaker, phases lined up, no one knows, phases crossed:thumbsdown: They do give a warning sticker that goes on the generator breaker telling you not to turn the breaker on if the panel cover is off.
kwired
Electron manager
- Location
- NE Nebraska
There is no limit to how many transfer switches may be supplied by a generator.
In fact when you get into hospitals there are instances where more then one transfer switch on a single generator may even be required.
In fact when you get into hospitals there are instances where more then one transfer switch on a single generator may even be required.
GerryB
Senior Member
- Location
- woodbridge, ct. USA
That's interesting. I'm going to ask the city inspector when I see him. He used to do a lot of hospital work before becoming the EI. To answer Augie's question it is a 9 or10kw portable generator.
At least its not smaller
In any event, it will be an interesting show to see the homeownerselecting which breakers to turn off before the generator stalls...
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