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I am adding a 50 amp sub panel to my shed. I am using thwn 6 awg wire in pvc conduit. I have installed a ground rod to sub in shed also. Here are the questions I have conduit that leads straight to a sub panel next to main. Can I feed 50 amp sub off a 60 amp sub? Also the 60 amp sub next to main only has 2 hots and a neutral no ground wire it is bonded do I need to bring new sub in shed to main? Also shouldn't my 60 amp sub have a ground to main? I hope I did not confuse anyone

 

[surferdude2]

I understand why you would want to run from the existing sub panel... it's easier to get to. That will be OK... you will have to add an equipment ground bar or a ground lug, if none is in that sub panel, assuming it's being grounded via a metal conduit back to the service. A 2-pole 50 is fine with #6 awg wire. I suggest spending the extra and getting a gfci rated breaker.

Be sure to use thwn rated wire or uf cable for the u/g pvc run to shed, per code requirement. I'd go with individual thwn wires since it will pull easier. Use #10 copper for the ground.

 

[[email protected]]

Their is no metal conduit between two current panels. do I need to run a ground from one to the other?

 

[surferdude2]

Yes, you are required to have a #10 copper or #8 aluminum Equipment Grounding Conductor, based on the size feeders needed for a 60 amp sub panel.

 

[seharper]

Crossposted, photos and discussion here.

 

[surferdude2]

I am adding a 50 amp sub panel to my shed. I am using thwn 6 awg wire in pvc conduit. I have installed a ground rod to sub in shed also. Here are the questions I have conduit that leads straight to a sub panel next to main. Can I feed 50 amp sub off a 60 amp sub? Also the 60 amp sub next to main only has 2 hots and a neutral no ground wire it is bonded do I need to bring new sub in shed to main? Also shouldn't my 60 amp sub have a ground to main? I hope I did not confuse anyone

That's a code violation... bonding the neutral to the panel is only required and allowed in the main panel. Remove any bonding and add the Equipment Grounding Conductor that I mentioned to bring it up to code.

 

[seharper]

Yeah, you can't have a subpanel with just H-H-N feeds and bootlegging ground off neutral. If the neutral wire had a problem, it would energize all the subpanel's grounds!

So you'll need to get some accessory ground bars for the panel (often the neutral bars can be split, but that's not worth the hassle and you're just shorting yourself screws at that point).

Retrofit a ground wire between main and subpanel. It doesn't need to follow the same route.

Move all the grounds to those ground bars.

Remove the neutral-ground bonding screw/strap on the neutral bar.

At that point you should be able to measure millivolts of difference in voltage between the neutral and ground bars, when one leg is heavily loaded (e.g. 1500W heater plugged into one leg), and that difference should change with load.