Outlet wire connection

Status
Not open for further replies.
P

PowerdT

Senior Member
Location
San Diego
Occupation
Electrical Engineer
I have outlet type NEMA L21-30R, it is 208V, 3phase, 30A, 4 Pole, 5W. I have seen it Connected in lab at 3 pole. Can someone please help me how is it possible?
 
I meant in the lab there is L21-30R receptacle and it is using 3 pole breaker in the panel. Does that mean there is no neutral wire or is it possible there is neutral but no switch
 
There is a 3 phase receptacle fed from a 3 pole circuit breaker so what do see as a problem? The receptacle has no neutral?
 
An L21-30R is a three phase with neutral and ground receptacle. For it to be properly wired you would need the three phases and neutral from the panel. 208/208/208/120 with ground.

That said, someone could certainly just wire it without the neutral, but that would create a situation where equipment requiring the neutral could be plugged into the receptacle with not so good consequences.

This is why we have specific receptacle configurations- so only the correct plug can be inserted in the receptacle that provides the proper voltages and current for the equipment.

-Hal
 
infinity said:
There is a 3 phase receptacle fed from a 3 pole circuit breaker so what do see as a problem? The receptacle has no neutral?
Click to expand...
I am trying to understand that the specification data for L21-30R says 4 pole so I want to know is it possible they connect 3 hot + 1 neutral + ground and use 3 pole breakers
 
hbiss said:
An L21-30R is a three phase with neutral and ground receptacle. For it to be properly wired you would need the three phases and neutral from the panel. 208/208/208/120 with ground.

That said, someone could certainly just wire it without the neutral, but that would create a situation where equipment requiring the neutral could be plugged into the receptacle with not so good consequences.

This is why we have specific receptacle configurations- so only the correct plug can be inserted in the receptacle that provides the proper voltages and current for the equipment.

-Hal
Click to expand...
Can you connect the L21-30R, 120/208v, 3 hot + 1 hot + 1 ground in 3 pole breaker?
 
hbiss said:
Perhaps you should have an electrician do this for you.

-Hal
Click to expand...
Yes an electrician will be installing this. I am designer trying to understand the data spec specifying 4 pole, 5W and the existing outlet installation has 3pole breaker that’s where I got lost
 
Etanuye said:
Yes an electrician will be installing this. I am designer trying to understand the data spec specifying 4 pole, 5W and the existing outlet installation has 3pole breaker that’s where I got lost
Click to expand...
You need to provide a 5-wire circuit: ABC-N-EGC. The ABC is fed from the 3 pole circuit breaker. The other two conductors are from their respective buses in the panelboard. The EGC can be a metal raceway if applicable.
 
infinity said:
You need to provide a 5-wire circuit: ABC-N-EGC. The ABC is fed from the 3 pole circuit breaker. The other two conductors are from their respective buses in the panelboard. The EGC can be a metal raceway if applicable.
Click to expand...
Thank you. That explains it.
 
Etanuye said:
I am trying to understand that the specification data for L21-30R says 4 pole so I want to know is it possible they connect 3 hot + 1 neutral + ground and use 3 pole breakers
Click to expand...
This is just a confusion of terminology.

They consider the neutral to be a "pole" of the receptacle; the breaker does not include the neutral.
 
Yup. 'Pole' describes the number of circuit conductors connected or switched.

A 3 pole breaker switches 3 circuit conductors.

A 4 pole receptacle carrys 4 circuit conductors.

The combination of a 3 pole breaker and a 4 pole receptacle is correct because the neutral is not switched.

The EGC is in addition to the circuit conductors, so you will have a 4 pole 5 wire receptacle.

Jon
 
Status
Not open for further replies.
Top