208v 3phase vs 208v single phase

[JMS1990]

A 3 phase 208v machine uses a 50 amp plug 4W 3Phase. It is protected by a 3 pole 35 amp breaker.

Elsewhere there is the exact same 50 amp 4w 3 ph plug however it is only protected by a 2 pole 40 amp breaker and is only single phase 208v.

Can I plug this 3 ph 208v machine into the single phase 208 v plug given that it is the same plug configuration?

 

[Hv&Lv]

A 3 phase 208v machine uses a 50 amp plug 4W 3Phase. It is protected by a 3 pole 35 amp breaker.

Elsewhere there is the exact same 50 amp 4w 3 ph plug however it is only protected by a 2 pole 40 amp breaker and is only single phase 208v.

Can I plug this 3 ph 208v machine into the single phase 208 v plug given that it is the same plug configuration?

Your saying they all are 14-50 R(P)?
Sure you can plug it in. The machine will single phase and probably won’t start.

 

[winnie]

Your saying they all are 14-50 R(P)?
Sure you can plug it in. The machine will single phase and probably won’t start.

If you are lucky the machine simply won't start.

If you are unlucky the machine will try to start and burn out

 

[Jraef]

Your saying they all are 14-50 R(P)?
Sure you can plug it in. The machine will single phase and probably won’t start.

Definitely won't start if there is a 3 phase motor in it.

 

[EC Dan]

While I don't think it's necessarily a violation of the non-interchangeability rules in 406.4(F) and 406.8, that single-phase receptacle really ought to be replaced with the correct type to prevent someone from accidentally making this mistake.

 

[Hv&Lv]

Definitely won't start if there is a 3 phase motor in it.

Agree, but OP didn’t say what the machine was.
Heck for all I know, it could be using all three phases to power nothing but 120V loads..

 

[Dennis Alwon]

I think the op wants to bring 3 phase to a single phase receptacle.

 

[LarryFine]

No, a 3ph machine will not work when plugged into 1ph receptacle (not "plug"). As suggested above by the others, the 1ph circuits should have 3-wire receptacles, not 4-wire.

Presuming all are wired correctly, a 1ph machine should work anywhere, but you would have to rewire the 1ph receptacles to be 3ph for the 3ph machines to work anywhere.

 

[Little Bill]

I think the op wants to bring 3 phase to a single phase receptacle.

No, he's asking if he can plug in the 3 phase machine into a single phase receptacle. The receptacle is the same configuration but lacks the 3rd leg.

 

[scrypps]

This question bothers me because 4-wire equipment is normally three phase equipment, but a 4-wire receptacle normally means two hots, a neutral, and an equipment ground.

 

[LarryFine]

This question bothers me because 4-wire equipment is normally three phase equipment, but a 4-wire receptacle normally means two hots, a neutral, and an equipment ground.

That's why there are different NEMA configurations for 3ph 4-wire and for 1ph 4-wire.

 

[tortuga]

The OP lists their location as Ontario, so if this is under the CEC it is a violation of 26-7001 to not go by the NEMA chart
"Receptacle configurations shall be in accordance with Diagrams 1 and 2"
There are exceptions.

 

[winnie]

A 3 pole 4 wire receptacle could either be single phase H-H-N-G or three phase H-H-H-G . These are different receptacle configurations.

Unfortunately sometimes the ground does count (for example in SO cord) and sometimes it doesn't (NM cable) and sometimes two counts are given (plugs and receptacles where poles are circuit conductors but wires count the ground).

If you have both single and 3 phase receptacles in one facility you are supposed to use different receptacle configurations.

Jon