120/240V panel… All loads are 120V…

[Cindysparky]

Simple problem that I’m not sure of the answer: 120/240V panel. All loads are 120V

I’m assuming you just take A phase minus B phase to calculate the Amps on the neutral. Am I correct?

Thanks

 

[zbang]

That works if the panel is actually supplied by a single-phase source and the voltages really are 120/240; some single phase "120/240" panels are supplied by two legs of a three-phase service so get 120/208.

 

[Cindysparky]

Yeah. I considered that. But it’s 100% a single phase

 

[LarryFine]

Welcome to the forum.

It's literally based on the maximum imbalanced load you can place on either line.

 

[Cindysparky]

That was my thought but the all 120V loads was throwing me off.

Thanks for the warm welcome

 

[roger]

For single phase 120/240 it's as simple as this illustration.

 

[Cindysparky]

I’ve seen that a million times for one a multi-wire branch circuit, but I didn’t want to oversimplify it for a panel feeding many circuits. Thanks everyone. I needed this help.

 

[LarryFine]

I’ve seen that a million times for one a multi-wire branch circuit, but I didn’t want to oversimplify it for a panel feeding many circuits.

A 120/240v feeder is an MWBC.

 

[Cindysparky]

A 120/240v feeder is an MWBC.

That’s awesome that you said that. So much clarity.

 

[roger]

A 120/240v feeder is an MWBC.

Well actually it's just a MWC.

 

[Cindysparky]

Well actually it's just a MWC.

That’s a funny little catch hahaha.

 

[eric stromberg]

Imagine a power failure on one line. If line 1 fails, what is the load on line 2? If line 2 fails, what is the load on line 1? Whatever the larger load is, is the minimum size for your neutral.