Panel Voltage Identification Labels

[Karl H]

On a 208 3 phase panel should the tag read 208/120 or 120/208?

480 3 phase- 480/277 or 277/480?

 

[tom baker]

There probably is an IEEE Standard, this is the NEC
220.5 Calculations.
(A) Voltages. Unless other voltages are specified, for purposes of calculating branch-circuit and feeder loads, nominal system voltages of 120, 120/240, 208Y/120, 240, 347, 480Y/277, 480, 600Y/347, and 600 volts shall be used.

 

[Karl H]

Thanks Tom,

The reason I posted this question is for "Back-up" for a debate I was having
with a facilities manager. I received an e-mail from this guy saying all
of my panel labels were wrong,and that they should read 120/208 and not 208/120 as he "used" to be a electrician. I replied "these are 3 phase panels
and 120/208 was a single phase panel." Well this guy that "used to be" an electrician wouldn't hear any of my explanation so I thought I'd post it
here on the forum, get a response and forward it to him.

Don't get me wrong ,this guy is real smart, and this was a friendly debate.
I just thought I'd give him a "ribbing" on this one.

 

[infinity]

Whether a panel is labeled 120/208 or 208/120, IMO everyone will know that it's a 3 phase, 4wire, Wye panel.

 

[iwire]

A couple of posts from Jim D in other threads on this subject

The preferred ANSI method is:

120/240 single phase

208Y/120 three phase

240/120 three phase

480Y/277 three phase


Supply systems are listed at the nominal voltages listed in the NEC, 120, 208, 240, 480, and 600V.

Motors are listed at utilization voltages of 115, 200, 230, 460, and 575V.

Connecting types of devices like lamp holders and fuse holders are listed at a maximum voltage of 125, 250 and 600V.

Plugs and receptacles are listed based on their specific configuration.

It seems that appliances may be listed at no specific voltage method.

Now, just to be picky. The ANSI/IEEE convention for naming system voltages is:

Multi-wire grounded (bonded) single phase - list the L-G voltage first, then a forward slash and then the L-L voltage: 120/240 or in this case 104/208.

Multi-wire grounded (bonded) three phase - list the L-L voltage first, then the letter Y if applicable, then a forward slash, and finally the L-G voltage: 208Y/120, 480Y/277, and 240/120.

I have spent 30yrs trying to unlearn the bad habit of saying 120/208V. Now I try (but often fail) to include the number of phases and wires, as I find it does reduce confusion, for example: 120/240V 1PH3W and 240/120 3PH 4W

 

[Karl H]

All of my ID's have 3 phase 4W or three phase 3W along with the system
voltage. I wonder how this all came about,installing tags.
I bet It was designers getting nailed specifying line/neutral loads
from 3 phase 3W mechanical panels. That's just a guess.