3 phase sub panel wiring. Neutral conductor sizing for 120v

[JDL988]

Hello, I am installing a 20hp phase converter, I would like to set up the 3 phase sub panel to use 120v off it so I can run a hand full of read outs, lights, coolant pumps and such so I don't need to run extra circuits to run those items from the single phase service entrance panel. How can I determine what size THHN to use from the service entrance panel to the 3 phase sub?

Would I just determine how many amps in total of 120v accessories I would use, use the 80% conductor rule and then size the wire from there? Thanks

 

[Norcal]

Don't use the panel for a RPC for single phase loads, just not a good idea.

 

[micromind]

I agree.

If needed, set 2 panels, one single phase for 120 and 240 single phase loads and the other for 3 phase loads only. I know it's a hassle but the first time you connect a 120 load to the manufactured phase..........

If you understand 3 phase systems, you can use 1 - 3 phase panel and treat it like a high-leg delta system.

 

[wyliesdiesels]

yeah thats a bad idea.

 

[rlitman]

Don't use the panel for a RPC for single phase loads, just not a good idea.

To elaborate, the single phase loads will create a huge amount of harmonic noise on your tiny 3-phase grid. Stick to delta with this one and you'll be much better off.