Small 480V panel with 20 amp MCB?

[bmabe]

New member so appreciate any help. We manufacture lighting fixtures and assemble electrical systems for portable military shelters, AKA large tents. Most often the specs are minimal or at best obscure.

A current RFQ calls for (12) 400 watt MH 480V floodlights in a structure which should only draw 12 amps. We need to supply PDPs (Power Distribution Panels) for the structures to handle the overload protection for the lights. They will be hardwired to "base supplied power", i.e., 480Y/277V. Technically, this would be a service entrance panel. For a recent series of much larger structures, we supplied SquareD NL panels with 200A MCB.

Can anyone suggest a simpler, more economical, and smaller panel to use in this situation than the NL panel?

 

[augie47]

How about a fusible disconnect ?

 

[wireguru]

how many of these panels will you need? Perhaps you should have something made. Do you need just a 20a breaker, or do you need it as a 20 amp main and branch circuit protection for each light?

 

[bmabe]

Thanks for the quick response.

I'm finding 30 amp fusible disconnects as the minimum size. Since these structures have only a 12 amp load, would a 20 amp 3 pole 600V rated CB in an enclosure with a single branch, qualify as a service entrance under code?

Thanks,
bmabe

 

[bmabe]

There are 12 individual structures and location in relationship to each other is unknown. I think that a 20A CB serving as a main and branch circuit protection would fulfill the requirements, if this is for a suitable service entrance.

 

[Jraef]

So you want one 20A 3P breaker in a box with a SUSE label on it? No need to buy an entire panelboard, you can just buy an enclosed circuit breaker.

The problem is, you MUST know the the Available Fault Current of the service to get a SUSE label on an enclosed breaker, otherwise the only safe approach is to buy a breaker with 100kAIC or maybe 65kAIC, and that is going to be expensive compared to a Fusible Disconnect. The current ratings on fusible disconnects are just MAXIMUM for the switch mechanism and fuse clip spacings, so what you would do is buy a 30A FD and put in 20A or even 15A fuses. A FD will likely have 200kAIC with the right fuses, (RK1 or RK5) so you can dispense with worrying about the AFC too much.

 

[hillbilly1]

A 30 amp disconnect with 20 amp fuses would definetly be the cheapest and easiest way, as far as fault current is concerned, use the correct AIC fuse disconnect.

 

[bmabe]

Thanks to all. We will run both options past the base electrical engineer. Appreciate the clarification on using a 20 amp fuse in a 30 fusible disconnect.

bmabe