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2014 NEC 690.7 Maximum System Voltage 600V and 1000V Distinctions


Q:

Article 690 - Part II - 690.7(C): Maximum System Voltage. In your lecture you mentioned that the NEC distinguishes between 3 family dwellings (up to 1000V PV max system voltage), versus 1-2 family dwellings (up to 6000V PV max system voltage). Two questions: First, I proudly bought the book, but I do not see this distinction in 690.7. From what I read, it addresses 600V and 1000V. Second, it seems arbitrary to distinguish to maximum inverter size between 3 family dwellings vs. 1-2 family dwellings. Do you think this will change? Wouldn't you want ideally to have one string on one inverter versus breaking strings out onto multiple inverters, or to run the system in parallel?

A:

The rules are the rules. The 2014 NEC changed to allowing 1000V PV systems, however 1 and 2 family dwellings were still limited to 600V.
Personally, I would feel safe with a 1000V system on my roof. If you start looking at buildings that are more than 1 and 2 family dwellings, it is more commercial property.
Often times with smaller PV systems, there is no need to go over 600V since we are always trying to fit PV on a rooftop and it is often difficult to fit 20 modules on a normal house facing all in the same direction.
Also, with the 2014 NEC we are more likely to see electronics under modules on rooftops, so that is another reason we will not be needing to go over 1000V.
I dare you to put a 1001V system on your roof (don't tell anyone).
Thanks,
Sean


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