You are watching: What size ground wire for 125 amp service
If your local electric inspectors allow the use of NEC table 310.15(B)(6) because that residential below panel feeders, then #2 copper is acceptable because that 125A. (residential key feeder rule)If your pack calculations come in at much less than 115A, climate #2 copper might be safeguarded with a 125A breaker. (round increase rule)Otherwise girlfriend will have to use #1 copper for her conductors.Voltage drop need to not it is in a far-reaching issue at this distance.-Jon
Since I have not yet bought the wire, then i may as well get #1. Phoenix provides the NEC so it will be ok. Yet existing conduit is in the attic and also is RNC (pvc Sched 40) 1.25". Looks a little tight because that #1..... To fill chart says I to be ok..... What dimension ground would certainly I then use??? #4 ???? and can I use insulated wire for soil THHN..... I have some already... Thanks
Since you are using a 100 amp breaker to feed this dashboard you have the right to most most likely use 310.15(B)(6) i beg your pardon will enable #4cu for the hots and also neutral. A #8 floor is all that is needed.Just double check v your regional code office to check out if this chart is provided in your area. That is in mine.
I plan to use at least #2. I may want to broaden its consumption later, you never know. I recognize I cant walk behyond the 125A, therefore if I want to plan for later and also still use a 100A breaker because that now, must I walk #1 or will certainly #2 work-related ok???? If its in the NEC climate my inspector said he will accept it.... Ground size for #2 is #6?? What ground because that #1 ??????/ many thanks again
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That would certainly be a large whoops on mine part.I observed the 125A dashboard number but not the 100A breaker number. My above assessment thus changes to:If your local electric inspectors allow the use of NEC table 310.15(B)(6) for residential below panel feeders, climate #4 copper is acceptable for 100A. (residential key feeder rule)If your fill calculations come in at less than 85A, climate #4 copper may be defended with a 90A breaker. (round increase rule) (This is if the over statement doesn"t apply.)Otherwise you will have to use #3 copper for her conductors defended by the 100A breaker.Voltage drop should not it is in a significant issue at this distance.The minimum size for the equipment grounding conductor would be #8 copper. It have the right to be _green_ insulated THHN, bare, or _larger_ the #6 copper and marked with environment-friendly tape at the ends. -Jon