Wrenches,

A couple of quick thoughts about AC disconnects.

We installed a grid-connected system last April and the homeowner has somehow since then lost the main breaker panel cover plate.  The homeowner had a new air conditioner installed last summer as well as a new outdoor lighting.  The breakers are no longer labeled.  ( I know, a monkey can trace wires)  Now we get to the issue of servicing inverters.  We have been installing GC-1000’s, which are proving to be very reliable.  That said, a GC-1000  needed replacement about a week ago.  Marko Rosenfeldt from Advanced Energy showed up with a new replacement unit.  The fault was found on the motherboard on the upper half of the inverter.  So as not to have to cover 20 modules and disconnect the DC strings connected on the lower half (at noon time), it was easier to just change out the upper half.  The GC-1000 has the AC connections inside the inverter on the upper half and the internal AC disconnect is on the lower half.  Having a secondary AC disconnect on the AC line made the change out quick and safe. This was not the same house with the non-labeled breakers but these things can happen.  What bothers me is the “lockable” feature that is mandated by the utilities.

I have full confidence with anti-islanding but the average homeowner may not be as confident.  I explain to customers that if the grid drops out the solar power is disabled. I also mention that if they open the main breaker to perform any electrical work that they may want to open the labeled AC solar disconnect, if it makes them feel safer.  I don’t want my customers to ever have any fear of electrocution.  A non-fused disconnect and labor only adds about a hundred dollars to the installed cost.  Redundancy may perhaps be a good thing.

P.S. Thanks Marko - your support and speedy service is greatly appreciated.