Quote:
Originally Posted by sylar
is this actually unsafe? when i looked a couple of months ago, most connected solar inverters will shut themselves off if they detect no current coming from the grid. i.e. firefighters should still be able to shut off the power. is this incorrect?
As far as I know, no firefighter in America has been killed by a solar array and there's a fair chance I'd hear about it as the few times an installer has died (from falling of the roof or ladder every time I've heard of) it seems like word gets around.
In California (and probably elsewhere too) there are guidelines from the State Fire Marshall designed to protect firefighters and allow them to fight a fire on a structure with solar. The rules include pathways for the firefighters, clear space at the ridge so that the roof can be vented, labeling and rules about the conductors in attics to keep them away from chain saws.
Ok, now to get to your question.
The inverters automatically shut down on a grid connected system because otherwise when the power were out the system could continue to supply energy to the utility lines, which could shock unsuspecting utility personnel working on the lines.
The solar modules (panels) don't turn off when the inverter turns off. If you have a system with a central inverter and solar modules strung together you can have voltages on residential systems up to 600 volts. With the inverter off that's just voltage - potential - there's nowhere for the current to go. But, if your body became part of a circuit because you put your axe into a conductor while another part of your body were grounded, you could get shocked.
(a few things left out to avoid complication - there are ungrounded systems - microinverters or power conditioners change the answer)