600v vs 1000v solar panels for residential use

[rkerkhof888]

I am a newbie and see that there are some solar panels that are rated 600v, some 1000v, and some are rated both. What is the difference? I understand that solar systems for residential use are limited to 600v but could I use 1000v panels even though I would never get anywhere near 1000v (ie. 10 250 watt panels in series VOC of 38.1v) and would be using a 600v inverter. Could there be a permitting problem if they see 1000v panels vs panels that are rated both 600v and 1000v?

Still learning.
Thanks, Rudy

[sensij]

No problem using 1000 V panels. The code requirements are for a minimum rating, not a maximum.

[Sunking]

Back ground story is last code cycle USA was 600 limit, and Europe were 1000 volt limit. In the USA you could use either panel with a 600 volt limit in application, but could not use USA rated panels in Europe. Today in the USA code cycle 1000 volt is the limit with respect to panels. The Benefit if not obvious already is the higher voltage allows for higher power without increasing current thus keeping copper cost down.

[inetdog]

Just as you are allowed to use 600V rated wire for 120V circuits, the "system voltage" listing for the panel is just an indication that it can be used safely up to that voltage.

The code writers were willing to update the requirements for PV installations on non-residential sites to 1000V, particularly with the introduction of the PV wire type with 1000V and 2000V insulation options, not just 600V. But they apparently felt that for the unsupervised residential environment it just was not yet the right time to allow 1000V systems.
Also the higher voltages can lead to lower efficiencies in residential systems where the POCO supply is generally limited to 120/240V single phase, and wire runs are typically shorter than in commercial scale systems. Thus the motivation for extending the upper limit to 1000V is not as strong.

[Naptown]

Back ground story is last code cycle USA was 600 limit, and Europe were 1000 volt limit. In the USA you could use either panel with a 600 volt limit in application, but could not use USA rated panels in Europe. Today in the USA code cycle 1000 volt is the limit with respect to panels. The Benefit if not obvious already is the higher voltage allows for higher power without increasing current thus keeping copper cost down.

I have to read the code but 600V is residential and 1000V is OK for commercial. Has this changed with the 2014 code?

[rkerkhof888]

I am a newbie and see that there are some solar panels that are rated 600v, some 1000v, and some are rated both. What is the difference? I understand that solar systems for residential use are limited to 600v but could I use 1000v panels even though I would never get anywhere near 1000v (ie. 10 250 watt panels in series VOC of 38.1v) and would be using a 600v inverter. Could there be a permitting problem if they see 1000v panels vs panels that are rated both 600v and 1000v?

Still learning.
Thanks, Rudy

Thanks you all so much. I read how 1000v panels are going to become the norm for commercial use and figured they were okay for residential but wasn't sure. I was just afraid an inspector would flag this as a potential problem. All the panels spec sheets show the rating as maximum ratings. Thanks again. Rudy

[Sunking]

I have to read the code but 600V is residential and 1000V is OK for commercial. Has this changed with the 2014 code?

No I think you are correct. IO am a commercial guy, not residential.

[Sunking]

I was just afraid an inspector would flag this as a potential problem.

No worries my friend. Code is minimum acceptable requirements. Absolutely no problem exceeding minimum requirements. Another example is a 20 amp Breaker requires a minimum 12 AWG copper wire. If the Inspector sees a #6 AWG on a 20 amp breaker, he moves on and will not say a thing, other than maybe say; You Over killed it. So inspectors do not have any problem shooting a dead horse, you just wasted a bullet which is not a code issue.

[SunEagle]

That 1000v rating on the panel may just be a specification the manufacturer put on to get the customer to think it is better than a panel rated 600v.

It still comes down to what dc voltage the NEC will allow in residential installations.

Has there been any recent changes by the string inverter manufacturers to meet that 1000v rating?

[Naptown]

Commercial yes 1000 v has been around for a while
Residential still limited to 600v