have to figure out how many lighting circuits required? Please help. Really apprecia

[Matt Mckenzie]

Before we calculate the neutral, we have to figure out how many lighting circuits are required for the lighting load. Correct? I took a class that said on a single phase circuit you just add up all the 120volt loads and divide by 120volt which is wrong... That is ridiculous. Thank you for the help!

 

[kwired]

If on a single phase two wire supply - what comes in one line has to go out the other line.

If on a multiwire supply depends a little on the supply system characteristics and how the loads are balanced across the neutral. Any individual branch circuit or section of a branch circuit with only two wires still goes back to what comes in one line has to go back out the other line though.

For basic circuit functionality purposes, when I say two wire circuit or even multiwire circuit it is disregarding equipment grounding conductors.

 

[kingpb]

Before we calculate the neutral, we have to figure out how many lighting circuits are required for the lighting load. Correct? I took a class that said on a single phase circuit you just add up all the 120volt loads and divide by 120volt which is wrong... That is ridiculous. Thank you for the help!

Why is that ridiculous? 10 lights draw 34VA each, that's 340VA; or 2.8 amps.

20A circuit, continuous load; 16A available. 16A x 120V = 1920VA

1920/34 = 56 lights, per 20A circuit.

 

[jglavin427]

And when you say you're calculating the neutral, keep in mind if you pull three single-phase (line-to-neutral) circuits as a multi-wire circuit with a shared neutral, and they originate from three different supply phases, those loads are out of phase from each other and thus will not be returning the full load current of all three loads combined on the neutral at any given time. In fact if they are balanced they will cancel each other out.