OCP for Tranformer secondary on a Construction Site Power Distribution Panel (Spider)

[buzzr]

480vac1ph primary w/150amp CB. 120/208 vac secondary feeding 10 ea 20amp GFCI receptacles & 4ea 2/50amp power receptacles.
I know NEC 240-4 tells me I need to have the Secondary OCP (which the Manufacturer neglected to install) So can I install a fuse block in the secondary between the Transformer and the panel lugs. or do I have to install a fusable disconnect switch.

If I decide to install a circuit breaker and back feed the panel can I use a 150A breaker.

thanks

 

[augie47]

I would say that in this situation, 240.40 would require a disconnect.
As far as the breaker goes, a back-fed breaker would be permissible, but depending on your panel, a 150 amp may not be possible as a back-fed.. As far as the amperage we need more info such as transf. kva, etc.

 

[iwire]

I know NEC 240-4 tells me I need to have the Secondary OCP (which the Manufacturer neglected to install) So can I install a fuse block in the secondary between the Transformer and the panel lugs. or do I have to install a fusable disconnect switch.

If this is manufactured and listed equipment the NEC does not apply and you should not modify it.

 

[Electric-Light]

There's a mistake somewhere. You can not derive 120 pole to center, 208 pole to pole from any single phase source.

 

[jim dungar]

There's a mistake somewhere. You can not derive 120 pole to center, 208 pole to pole from any single phase source.

You can if it is (2) hot legs/conductors and (1) neutral coming from a wye connected source.

This voltage source is very common to individual apartments in a large complex.

I wish there was a 'better' name for it than single phase (although some utilities call this a network).

 

[Electric-Light]

You can if it is (2) hot legs/conductors and (1) neutral coming from a wye connected source.

This voltage source is very common to individual apartments in a large complex.

I wish there was a 'better' name for it than single phase (although some utilities call this a network).

That's not really single phase. OP said 480v single phase, meaning two wires.
He didn't say 480/277 two leg.

 

[jim dungar]

That's not really single phase.

It is often called single phase as there is a single L-L voltage. There is no official (i.e. industry standard like ANSI or IEEE) method for classifying this system. Personally, I will usually call it 120/208 1Phase 3 wire.

OP said 480v single phase, meaning two wires.
He didn't say 480/277 two leg.

I agree.
Based on only the OP, it is likely his secondary voltage description is wrong.