RPC Question

[Little Bill]

If the load on an RPC is rotating the wrong way, will swapping the two single phase legs, not the derived 3rd leg, change the rotation?
Or would swapping one single phase leg with the derived 3rd leg change the rotation?

 

[LarryFine]

Either. Think of the RPC as a 3ph alternator.

 

[Little Bill]

Either. Think of the RPC as a 3ph alternator.

I've hooked up a few of them but never had to change rotation. The machines that were going to be used said where to land the generated leg.

 

[kwired]

I've hooked up a few of them but never had to change rotation. The machines that were going to be used said where to land the generated leg.

You do not want the generated leg to power any controls, it won't necessarily be a stable voltage nor will it necessarily be same voltage as the two input legs and can vary as load changes much more rapidly than the two input legs may vary.

 

[Little Bill]

You do not want the generated leg to power any controls, it won't necessarily be a stable voltage nor will it necessarily be same voltage as the two input legs and can vary as load changes much more rapidly than the two input legs may vary.

Yes, I know that the voltage on the generated leg is higher. Similar to a Delta high leg as the voltage measured around 208V on the generated leg from a 240V supply. That would not fare well with controls that need 120V.

 

[Little Bill]

I am working on a job of wiring a newly built office in a warehouse. They had an RPC in the space where the office was being built. Before I got there, the carpenters disconnected the RPC and moved it. They didn't bother to mark any of the conductors, just took them apart. So I will need to hook it back up without knowing the rotation, or how it was wired to get the proper rotation.

That aside, this RPC is really small and I've never saw one like this. It is just a motor with no cabinet for the capacitors and other things. There is a box on top of it that looks like a pecker head/wiring compartment, but is not where the whip comes out that connects to a JB. I didn't open it up but I can only assume the capacitors, etc. are in there.