KevMo
Gold Supporter
When determining the size of the wire needed, the size of the breaker upstream protecting the wire determines the size needed rather than the rating of the subpanel. A #8 wire can only be used if the upstream breaker is 50A or less. If you use a 100A breaker in the panel feeding the subpanel, you need at least a #3 gauge wire. Due to the 200' length, if you want to account for voltage loss of up to 5% when using 75A on the subpanel, you should use #2. Those gauges are for copper wire. You would need to increase by one size for aluminum.Also, I had my builder install a 100 amp sub panel and he is only running 8 gauge wiring to it. I spoke to him about it and said they normally only run 10 gauge but since I had spoken to him he was gonna size up. This seems way too small to me as it is about a 200ft run and I had a guy quote me a 100amp sub panel in the past and he was gonna run 2 gauge wire all the way back. I mentioned this to him and he thought it was gonna be overkill. Up to this point the builder has been solid, but I’m starting to have my doubts.