Voltage drop of individual loads?

[pr3dict]

So I'm trying to understand voltage drop and I think I understand it but then I don't.

When I am calculating my vdrop for a 240 sub panel I have to calculate the 120 loads separate right? There are 2 legs of 120 and if I have something connected that will use 50 amps on one leg then I need to calculate that when sizing the wire instead of using that same calculation at 240. I think I understand that correctly...

But what if I have 3 individual loads, 1 load using 20 amps, another using 20 amps, and a 3rd using 10 amps. Do I do calculations for the loads separately or will the voltage start to drop more as I turn on more loads?

 

[u2slow]

For a mixed 120/240V subfeed you do the vdrop calculations on 240V because you assume a balanced load. Only the unbalanced portion 'sees' the extra vdrop.

In the case of a say a 60A 120/240V subfeed, and a 50A/120V load, you'd give further consideration to vdrop (i.e. up the feeder size). If you had say a 100A subfeed, then its basically a wash.

Where are you finding a 50A/120V load?

 

[pr3dict]

For a mixed 120/240V subfeed you do the vdrop calculations on 240V because you assume a balanced load. Only the unbalanced portion 'sees' the extra vdrop.

In the case of a say a 60A 120/240V subfeed, and a 50A/120V load, you'd give further consideration to vdrop (i.e. up the feeder size). If you had say a 100A subfeed, then its basically a wash.

Where are you finding a 50A/120V load?

It's not really for the subpanel calculations as much as my generator I'm installing 300 ft from the house (for various reasons). I'ts a 22kw so ~100A. I'm using 4/0 wire to account for the V drop but I'm thinking what if Im using a bunch of 120 loads that will equal 50A?

Who knows... lol.

 

[u2slow]

but I'm thinking what if Im using a bunch of 120 loads that will equal 50A?

You would distribute the 120V loads evenly in the panel. i.e. eight 15A breakers; 4 on each hot leg. That way they are balanced and don't incur any more vdrop than a 240V load.

Got it?

 

[wyliesdiesels]

It's not really for the subpanel calculations as much as my generator I'm installing 300 ft from the house (for various reasons). I'ts a 22kw so ~100A. I'm using 4/0 wire to account for the V drop but I'm thinking what if Im using a bunch of 120 loads that will equal 50A?

Who knows... lol.

Are you feeding this generator into the main service panel or a subpanel?

 

[pr3dict]

You would distribute the 120V loads evenly in the panel. i.e. eight 15A breakers; 4 on each hot leg. That way they are balanced and don't incur any more vdrop than a 240V load.

Got it?

Yeah I get it kinda sorta

Are you feeding this generator into the main service panel or a subpanel?

It's going to a 200 amp ATS then to the main panel. I'm actually running 4/0 to the generator in the same trench that I'm running 1/0 to the sub panel for the garage. Too bad there isn't a way to use the same wire lol.