Sub panel - Running sub panel off sub panel or 2 sub panels?I

[digdug18]

I need to run a sub panel to the garage, location would be light green; Also a sub panel to the shed which is on the right.

Should I run a sub panel off of a sub panel or seperate circuit to run a 2nd sub panel? I'd imagine a 2nd sub panel would be best for isolation, but I'm not an electrician.

Both subpanels would be 230v 50amps, planning on using 6 guage copper, 4 conductors in pvc for the underground portion. I want to move the air compressor to the shed so that it's less noisy, and still have power in the garage for welders, ovens, etc for projects.

Thoughts?

 

[mm08822]

I would make the garage sub panel fed with #2 SER alum (4 conductor) with 90a cb in main panel. Would handle all your needs and 1-2 future evs.

Feed shed off of new garage sub with 4 wire feeder in conduit. Alum conductors in conduit. Forget copper $$$.

 

[PCustoms]

Nothing wrong with a sub off a sub.

Does anyone actually by copper feeder anymore?

 

[Cruzan80]

Just remember, the total feed for both sub panels (if one is fed off the other) would be 50A (total, at the same time), or whatever the first panel is connected to at the main breaker. Otherwise, if you wanted 50A available at each panel at the same time (one feeding the other), you would need 100A to the first panel. Or you would need two dedicated runs each breakered at the main for the max you want at each.

 

[PCustoms]

Just remember, the total feed for both sub panels (if one is fed off the other) would be 50A (total, at the same time), or whatever the first panel is connected to at the main breaker. Otherwise, if you wanted 50A available at each panel at the same time (one feeding the other), you would need 100A to the first panel. Or you would need two dedicated runs each breakered at the main for the max you want at each.

I believe the correct way to size everything would be a load calc at each sub, and then size the feed accordingly to the 1st subs load.

 

[Cruzan80]

Yes for sizing each load to what is needed. What I meant was simply that if there were 30A draw at one panel (from only circuits from that panel, not including the second sub) and 28A draw at the second panel (random made up numbers) and they were fed Main->Sub1->Sub2, it would flip the breaker feeding Sub1, thereby turning off both panels, due to the 50A breaker in the main

 

[wyliesdiesels]

how full is your main panel?

what loads will you have in the garage and shed?

how easy is the run thru the house?

personally I would feed the garage with #1 SER and 100a breaker and then feed the shed from that panel like mm08822 suggested above.

forget #6 cu...

 

[dscheidt]

Nothing wrong with a sub off a sub.

Does anyone actually by copper feeder anymore?

probably only where conduit fill is the limiting factor. (a 60A sub takes 6 awg copper, so will fit in a 3/4 emt, Al requires 4, and needs 1")