New service ground/wire question

I-expo · Dec 19, 2021

New here, thanks in advance for any help! My question is-

I am building a new house/shop, my main 200 service and panel is on the pole and I will have a 200 amp sub panel in the house/shop. I know the main panel is to be bonded and the sub panel is unbonded. My question is for the sub panel what wire size do I need to run (250’ underground) and do I run a ground wire from the main panel to the sub panel or do I just drive my 2 grounding rods in for the subpanel? My thought is if the main panel is bonded and I run a ground from it and even though the sub panel is unbonded won’t there still be continuity between the ground and neutral in the sub panel since the main is bonded?

Megawatt · Jan 3, 2022

I-expo said:
New here, thanks in advance for any help! My question is-

I am building a new house/shop, my main 200 service and panel is on the pole and I will have a 200 amp sub panel in the house/shop. I know the main panel is to be bonded and the sub panel is unbonded. My question is for the sub panel what wire size do I need to run (250’ underground) and do I run a ground wire from the main panel to the sub panel or do I just drive my 2 grounding rods in for the subpanel? My thought is if the main panel is bonded and I run a ground from it and even though the sub panel is unbonded won’t there still be continuity between the ground and neutral in the sub panel since the main is bonded?

You are exactly right on sub panels being fed from the main panel you pull 4 wires with one of them being your equipment ground which goes to it’s own ground bar and no ground rods are not required. For your wire size to a 100 amp panel or 90 amp you will need three # 3 copper with #6 ground copper. For aluminum it would be 1/0x3 with a # 8 ground. If you need more information please come back and sorry for the delay