[RE-wrenches] AFCI problems with SMA RSB

[Bruce Erickson]

Hi All,

I’m wondering if anyone else is having trouble with the SMA Rapid Shutdown Box. We have an installation where an SMA 7700TL-US-22 (rebranded as SunPower) is fed by an array with a Rapid Shutdown Box. Many, but not all, mornings, the inverter would fail the AFCI self-test on wakeup. When reset, it would operate fine all day. There was never an actual indication of an arc fault, just the self-test failure. SunPower, in consultation with SMA, decided to replace the inverter. Everything worked normally for a couple of weeks, then the problem resumed. Again, no arc-fault indication, just the self-test failure and then full operation the rest of the day after resetting. 

We began to suspect the Rapid Shutdown Box, so we bypassed it completely, and there were absolutely no problems for several weeks. SMA was then willing to replace the RSB, after which everything worked fine for about a week, then this morning the same issue. Again, self-test failure, then when reset, it has to go through another self-test, which it always passes and then runs all day.
Has anyone had problems with the RSB, or, with AFCI in general?

Based on this experience, this is the second and last RSB we’ve used, and have somewhat reluctantly gone to all micro inverters to meet rapid shutdown.

Bruce Erickson
Mendocino Solar Service
PO Box 1252
Mendocino, CA 95460
707-937-1701
707-937-1741 fax
bruce at mendocinosolar.com

Connecting Mendocino County to Solar Since 1994