New shop electrical question

[Peter Tremblay]

Hello all,

I just moved into a new shop space here in North Carolina (after having no shop for the last year).

It has quite a few plugs but I have yet to figure out if they are on more than one circuit so that I don't flip a breaker when using two or more large tools at once (ie. bandsaw and DC).

There is a plug along the wall that looks to be independent of the other wiring.


I think this is a 3 phase 240V plug but I'm not certain.

Does anyone know what type of plug this is?

My question is if there is anyway to wire a plug where I could power a 120V single phase motor off of this?

Thanks

[jasfrank]

Nema 15-20. 3 pole 20 amp. If its a small size. Could be 50 or 60 amps if its the large size. So yes for 3 phase. Maybe someone wired it in to use for 240 volt single phase use though, as its real rare for residential to have 3 phase service.
If you wanted to use it for 115v check with a meter if you had that voltage across the terminals, but you'ld still need a plug. It would probably be easier to change the outlet.

[Peter Tremblay]

Thank you 

It is a large plug around 3" across.

It's not a residence.  Is in the basement of an old gym building.  
The room looks to be a former laundry room.  
The gym was part of an orphanage and school.

[daddo]

You'd have a 3 pole breaker. Check voltage from the round ground to each leg.

Residential or commercial property?

[TDKPE]

I believe it's a 15-50, 50A, 250V, 3-phase.  The 15-20 is opposite hand, like looking at the 15-50 plug.

But I agree that unless you live in an apartment building, or the very odd residence with 3-phase power, or it's a commercial space, it's probably running 120/240V single-phase.  Look in the panel to see what is powering it.  And pop it open to see what the conductors are. 

If it's a 2-pole breaker, 240V or 120/240V single-phase.  Or 120/208V single-phase, though that would be a misapplication.  As would 120/240V on that receptacle.  
 

It's a mystery.  


Edit: In light of your last post, it probably is 3-phase, on a 3-pole breaker.

Edit 2: If it was the basement of a school or gym building, it (almost certainly) was wired by an electrician. So it would (almost certainly) have been wired correctly for the voltage, phase, and ampacity. But take nothing for granted, and check it.

[Roly]

One the older installations the neutral and ground were one of the same just like on single phase.  The new installations use a 5 wire receptacle where the neutral and ground are separated. Or on this installation a neutral was not needed.  
 On the motor question, the biggest problem is it is a 50 amp circuit.    Any phase to the neutral will give you 120 volts, but remember between any two phases you get 208 V, not 240 V.   Many motors are marked for this variation,  but not all.       Placing a fusesable disconnect fused at 20amps,  then to the standard outlet would work.    Replacing the 50 amp breaker with a 20 amp breaker may not work as it may not take the larger wire.   Roly

[Steve N]

Hey Padre, I have no electrical advice except seeing if one of the parishioner's is an electrician. He may be wanting to earn a few free God points for just in case


But it is a very good thing to see the "Bombe Chest" may soon be completed, also whenever you are on here it's a better place, classier.....

[Peter Tremblay]

You'd have a 3 pole breaker. Check voltage from the round ground to each leg.

Residential or commercial property?

Commercial

[Peter Tremblay]

Thanks, Steve.

[Peter Tremblay]

One the older installations the neutral and ground were one of the same just like on single phase.  The new installations use a 5 wire receptacle where the neutral and ground are separated. Or on this installation a neutral was not needed.  
 On the motor question, the biggest problem is it is a 50 amp circuit.    Any phase to the neutral will give you 120 volts, but remember between any two phases you get 208 V, not 240 V.   Many motors are marked for this variation,  but not all.       Placing a fusesable disconnect fused at 20amps,  then to the standard outlet would work.    Replacing the 50 amp breaker with a  20 amp breaker may not work as it may not take the larger wire.   Roly

Roly, 

I want to power a 120V single phase motor.

So can I power it with one phase and neutral?

I was thinking of wiring the male plug for this to take power from only one prong and neutral.  Will that get me safe 120V single phase?

Is there a problem with pulling 20 amps from a 50 amp circuit?