Single Phase Circuits on 3 Phase Subpanel

[cmelville42]

I have a 100A subpanel in my workshop. A 40A circuit provides L1/L2 to an American Rotary ADX20 phase converter that provides Delta 3 phase to a small sub-panel. Currently there is only one 20A 3 phase load in the panel. I would like to add a single phase 240V circuit utilizing just L1/L2, 40A for a welder. My understanding is that this is generally acceptable on a 3 phase service.

Anyone here running something similar or have advice? L1 and L2 are energized whether the converter is running or not.
Is it advisable to run the converter when the single phase circuit is in use, or is that unnecessary?
Since this is a one man shop, only one load will ever be in use at a time. The phase converter vendor is unwilling to tell me anything except 'consult an electrician'.

Thanks.

 

[micromind]

Why not add the new circuit to the 100A sub panel?

What you are proposing will work but it's not the right way to do it.

 

[Cruzan80]

Trying to figure out exactly what is going on. Is there a 100A 1Ph panel, that has a 40A circuit feeding the RPC? And the 3PH panel downstream of the RPC has a 20A load? If so, agree with micromind to just add the 40A welding circuit to the 100A panel.

Or is the sub panel referenced the 3ph panel, and getting power from the RPC?

 

[wyliesdiesels]

Dont feed the welder receptacle off the RPC feed. feed it off the 100a subpanel..

 

[cmelville42]

I would do as you all suggest but there are no remaining slots in the 1Ph panel. I was hoping to avoid putting in yet another 1PH subpanel, hence the desire to simply add a 1PH circuit to the 3PH panel.

 

[Norcal]

I would do as you all suggest but there are no remaining slots in the 1Ph panel. I was hoping to avoid putting in yet another 1PH subpanel, hence the desire to simply add a 1PH circuit to the 3PH panel.

I would not use a panel supplied from a RPC for anything other then 3Ø loads.

 

[Steve from Socal]

It is not to code BUT, how about using the 40 amp feed TO the RPC for a plug?

 

[mm08822]

Take some pics of the existing panel with cover off. Include mfr label with part number.

It may be easy to switch out the panel and get what you need now and for the future.

 

[cmelville42]

Thanks for the suggestions. Here are a couple photos of the 3PH subpanel.

 

[mm08822]

Pics of the single phase panel needed.

 

[mikedodge]

On 3 phase service yes single phase circuits are used all the time but not using a converter like that. Leave it for actual 3 phase loads only. They aren't meant to feed single phase circuits.

 

[cmelville42]

Here is the single phase panel. I'm not keen to switch it out. However, I do have a couple 20A 220 outlet circuits and one of them is very under utilized. I have a lot of outlets but rarely run more than 2 loads at a time on them; I could splice those in the panel and run them off a single breaker. That would provide the space for the welder circuit.

 

[theoldwizard1]

Here is the single phase panel. I'm not keen to switch it out. However, I do have a couple 20A 220 outlet circuits and one of them is very under utilized. I have a lot of outlets but rarely run more than 2 loads at a time on them; I could splice those in the panel and run them off a single breaker. That would provide the space for the welder circuit.

Swap in some tandem breakers and you will have space for another 240V circuit.

 

[mm08822]

Swap in some tandem breakers and you will have space for another 240V circuit.

Technically that panel can't take any tandems.

 

[mm08822]

Here is the single phase panel. I'm not keen to switch it out. However, I do have a couple 20A 220 outlet circuits and one of them is very under utilized. I have a lot of outlets but rarely run more than 2 loads at a time on them; I could splice those in the panel and run them off a single breaker. That would provide the space for the welder circuit.

That works for now, but what about next time? Doesn't that put you right back here?

If you provide a pic with the cover off, it may be easier than you think to do.

 

[wyliesdiesels]

Swap in some tandem breakers and you will have space for another 240V circuit.

thats a 20/20 panel. tandems not permitted

 

[alfredeneuman]

I was hoping to avoid putting in yet another 1PH subpanel.

It looks like you have no choice.

 

[theoldwizard1]

thats a 20/20 panel. tandems not permitted

What is a 20/20 panel ?

 

[mm08822]

replacing the 20/20 panel with a 40/40 may be quite simple. Need the pics.

 

[mm08822]

What is a 20/20 panel ?

The panel label indicates 20 spaces AND the number of circuits permitted out of it = 20. So it will not take any tandems per listing. Also gfci and afci cb's aren't available in tandems.

 

[wyliesdiesels]

What is a 20/20 panel ?

20 spaces 20 circuits.

if it was a 20/30, it could take tandems in half the spaces