Hi All.

I've got a nagging issue with the RCD on my DB sporadically tripping when switching between on-grid and off-grid.

My setup consists of two 5kva Kodak / Axpert inverters running in parallel, each hooked up to a different solar array and a single stack of pylontech batteries. The system is off-grid by default, and then on-gird in case the batteries drop too low (which happens about 12 or so days a year). The tricky bit is that I have two db boards that can be fed independently from the inverters or the grid.

Each of the DB has a 63A 2N0,2NC contactor to switch between on-grid (eskom) and off-grid (inverters). The contactors have 220v AC coils which are actuated by a relay with two independent contacts and supplied from the inverters (there is no point in switching off-grid if there is no power off-grid). The second set of contacts on the relay switches the earth between grid and inverters. The output from the contactors feed into an RCD and then to the rest of the circuit breakers. The only difference between the primary and secondary DBs is that the secondary also has a smartswitch that switches the geyser on and off.

Like I said: the RCD on the primary board trips sporadically when switching between gird and offgrid, and from what I can tell, the cause doesn't seem to be the relays / contactors as switching between batteries and gird on the inverters themselves cause the same issue.

I have no idea where to even start with this one. Any advice or tips would be greatly appreciated.

 

 

 

Yeah, nuisance tripping is a common issue with the Axperts. This was a massive topic at one point, you can read more here: 

 

However, TLDR, Neutral bonding is usually the solution... I would advise checking the earth current when this happens just to make sure its just enough to trip the earth leakage, if its like an amp or two there may be deeper issues at play.