[RE-wrenches] MX60 output trips with load

[Phil Schneider]

Wrenches,

We have an off-grid system (quad OB 3648s, two MX60s) with an MX60 output
breaker that is tripping unexpectedly, and haven't been able to troubleshoot
the problem.

The MX60 circuit with the problem has 16 Mitsubishi 170s (on a dual axis
tracker) and a 60A DC breaker between the MX and the DC positive bus.  When
operating, the MX generally shows less than 50A on the battery side in peak
charging conditions.

The owner is charging a RAV4 EV on a 240VAC, 50A circuit.  The MX output
breaker in question trips when this load is turned on.  This happens
regardless of battery SOC - even when MXs are in float.  Limiting the MX to
45A output did not work either.  The other MX also has 16 Mitsu 170s, but
they are fixed and do not have this problem.

The breakers have been switched out (with equivalent 60A breakers) with no
effect.  All terminations on the DC side have been checked.  MX #6 wiring is
being upgraded to #4 right now, with 70A breakers.

Outback was stumped.  Any other ideas out there?  Thanks...

P.

Phil Schneider
Creative Energies