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stevehull · 09-02-14, 06:58 AM

Ormstron

I did check the voltage and voltage drop at the input of the system - by the meter. I did this with a load test and put about a 300 amp load on and only got a 2 v drop.

This is the result of putting in large G copper (not aluminum) with 400 A total service. 100 A to two homes. 100 to large livestock barn (including office) and 100 for future shop (now under construction.

So by backfeeding to grid (from PV panels) I don't have to worry about a large resistance causing a significant voltage rise on mains. Excellent point that I did not think of.

I know ANSI speaks of code being 5% drop. Code is the MINIMUM standard and I would prefer to be better than that. The issue is how much better. I think a 3% voltage drop is about half that and is OK. I can reduce it to a 2.5% voltage drop with 5G wire, but with a lot more money.

Engineering is about getting the most for your $, but an electrician will tell you that it is all about safety as well. Trying to balance both.

Steve
ps - only will need a 12,000 btu AC unit - essentially nothing for load

09-02-14, 06:58 AM	#8
stevehull Steve Hull Join Date: Dec 2012 Location: hilly, tree covered Arcadia, OK USA Posts: 826 Thanks: 241 Thanked 165 Times in 123 Posts	Ormstron I did check the voltage and voltage drop at the input of the system - by the meter. I did this with a load test and put about a 300 amp load on and only got a 2 v drop. This is the result of putting in large G copper (not aluminum) with 400 A total service. 100 A to two homes. 100 to large livestock barn (including office) and 100 for future shop (now under construction. So by backfeeding to grid (from PV panels) I don't have to worry about a large resistance causing a significant voltage rise on mains. Excellent point that I did not think of. I know ANSI speaks of code being 5% drop. Code is the MINIMUM standard and I would prefer to be better than that. The issue is how much better. I think a 3% voltage drop is about half that and is OK. I can reduce it to a 2.5% voltage drop with 5G wire, but with a lot more money. Engineering is about getting the most for your $, but an electrician will tell you that it is all about safety as well. Trying to balance both. Steve ps - only will need a 12,000 btu AC unit - essentially nothing for load __________________ consulting on geothermal heating/cooling & rational energy use since 1990