Solar array disconnect

[memilanuk]

Question on circuit breakers used for isolation (vs. protection) on solar input wires:

On the one hand, I see a *lot* of builds with those single-pole, push button circuit breakers like this used for isolating the PV input from the panels.

On the other hand, I've seen other places that recommend a dual-pole circuit breaker, citing an NEC requirement to "simultaneously disconnect the PV system conductors that are not solidly grounded from all conductors of other wiring systems."

Given that RV's sometimes seem to fall between the cracks of the NEC proper... any words of wisdom on this?

 

[upnorthandpersonal]

Use a double pole in ungrounded (meaning no conductor is bonded to ground) installations, always. You can get these current paths if something goes wrong and you don't break both sides:



The reason is because you have a potential closed circuit that can burn your wires if you only have a breaker on one pole. For example, suppose you have a nice earthed frame on your solar panels (or the frame connects to the vehicle), but your set-up is floating (i.e, your + or - of the panel array is not grounded). Suppose you have one breaker in the + of the string, close to the panels. You're working on the panels (and you're under the impression that everything is disconnected since you turned off the breaker. You make an accidental short between + and your frame. No big deal, no circuit. However, imaging that an LED lamp somewhere up the chain (or charge controller, or...) is connected to your array and its negative became exposed and touches its metal earthed fixture (maybe someone else was working on the installation, but hey, no big deal because the breaker is off). However now you have a short across your panels through the earthing and you're potentially burning up wire, for example the ones on the LED fixture since they're probably smaller diameter ones.