Jul 11, 2004 06:35 am
Re: GFP breakers
The National Electrical Code (NEC)Article 690 demands that all PV array's mounted to the roof of multi family and single resident dwellings ( basicaly anywhere there are permanent sleeping arrangements) must have ground fault protection. I am not sure why ether, but its the code, (perhaps the NFPA "see's"* a potential for someone burning to death in there bed) and if a system is going to pass an inspection in the USA it should have it.
I have seen in writting, published by Square D, that thier QO breakers have a UL listed DC rating of upto 48 volts, but I have not seen it in writting for any other brand. I am not saying it doesnt exsist, just that I have not seen it in writting published by the manufatures. And I have asked for it.
Getting back to the 48 volt rating though. As for Square D's rating of 48 vdc, thats not for a 48 vdc nominal PV rating which could have an open circuit voltage of 84 volts. Even some 24 volt nominal PV array's could have an open circuit voltage higher than 48 vdc after calculating NEC Article 690 temperature factors.
As Photovoltaics become more mainstream more inspectors are going to strictly inforce these codes. I do not mean to imply that inspectors are not doing there job just that Article 690 has been a rather obscure article until recently and as for those system that have passed inpections I am sure they are safe in as much as; the wire sizing and, equipment rating are met. There was a time when GFP was required by Code and nobody manufactured it but systems got passed anyway.
* "see's" - Looking into an "live" electrical breaker panel one cannot "see" electricity but there is potential there. As it is true with all physical objects know to mankind they do not exist until they react to or have been reacted on by another object. Fire exists everywhere but as humans we cannot see it until there is potential, it has to react with somethng else. If you close your eyes you cannot see the world but you know it exists because you have the potential for your other sense's to react against other objects in the world.
