OT: Multiple disconnects with one handle ?

I have an application where there will be three independent 480V AC 3-phase sources coming into the same control enclosure.

The client requires that each of them have an independent disconnect (either fuses or a molded-case circuit breaker).

NFPA79 sections 5.3.1.4, 6.2.3, and 6.2.4 all agree that I need to interlock the door so it can't be opened without the disconnects being turned off. This interlock can be mechanical or electrical.

So the question is: Have any Forum members ever seen or installed a single cable-operated disconnect handle that operated more than one disconnect switch ?

Alternately, has anyone seen an electrical interlock that did not require a handle and traditional three-point door latch ?

where are the 3 power sources comming from?

this is the first and MOST important question.

per NEC 70 codebook (sorry, i don't have mine with me right now) only one power source is allowed per building.
in other words, you have the breaker panel of the building you are in and that's it. you cannot have power from another building comming into the building you are in.

maybe someone else can answer better.

you might try an electrical website such as mikeholt.com

regards,
james

I think I'm over-complicating this.

This isn't a conventional factory automation control enclosure; the operational requirements really do make it necessary to have three independent power sources for failover purposes.

Each vertically-operated disconnect handle has a very simple door-mounted hook that latches over a bar that extends from the disconnect handle.

I just need to rivet a hook in place on the door for each disconnect handle that I add.

Once all three disconnects are open, the door can be opened using a single handle and three-point latch.

If somebody wants to override all three disconnects, well, they'll need three guys to do it.

This is a restricted-access, trained-personnel-only, extremely well managed machine site, and I was just tripping over myself trying to cite and comply with the proper NFPA 79 sections with interlocks.

Use an electic solenoid. Make it easy on yourself

Eaton and Siemens make 6 pole disconnects for two speed motors. Might be worth calling them to see if you could get something bigger.

I worked on a Siemens (I think) panel and it had an estop circuit tied to it, if someone hit the estop it would drop out two 480V breakers, you could also use the door handle to open the circuit on one and it would drop out the second, I am sure you could tie three of them together

I've done it. I used an ABB cable disconnect handle and mounted the three breakers next to each other, then bolted the bails of the breaker operators together. Works just fine. I have built multiple copies of this panel.

The application was a little bit different. The panel is fed from a single master disconnect, however there are setup operations which require the assistance of the control system but which require LOTO. The three breakers on the one handle allow LOTO of all sections where motion is possible but allow the rest of the control system to remain powered.

ftp://ftp.moeller.net/DOCUMENTATION/AWB_MANUALS/h1407G0509_chapter_18-23.pdf
for starters
However it are two problems you address,
one is circuit breaking, maybe automatic take over?
and door opening safety (i would use three doors with separation, and one central door for three of them. all with doorswitches.
This way you can service one source without stopping the machine.
It is allowed to have power on the switch incoming contacts even with door open, as long as they are covered and proper labeled