SMA2500 HF RCD Tripping Problem

[19simon]

Hi there

Just finished a 2500w 10 panel installation with a SMA2500HF inverter. Its a TT installation with a 30ma RCD main switch - old Square D board.

Every time I power up the inverter, the RCD trips even with all the other circuits off. I performed a ramp test and the RCD trips at 18ma, a bit sensitive, but not overly so.

I called SMA and they said that the installation manual states that a 100ma RCD is required for HF series although I cant find it in the manual. I did once install a 2500HF to an MK 17th edition board with no problem.

One option is to ask for a replacement, the other is to install a main switch supplementary board.

Any one else had RCD problems with this inverter?

 

[fiardor]

1. Sunny boys dont like more than 1 ohm between live and neutral Zs.
2. You should not share the customers RCD with your own 16 amp mcb.
3. Yes SMA guidelines ask for a 100ma RCD but we have used 30ma main switch rcds and they have been fine.

 

[screwdriver]

Firstly, I agree with Fiardor, For a TT system I would be looking at fitting a separate consumer unit with rcd main switch, 100ma preferably, especially with an old square d board which would be 'slightly' old! If it has that age board then you may be worth offering a consumer unit upgrade to the customer with a split rcd and separate rcbo for the inverter.

on another point, if you just want to get it running and then pop back after deadline, have you disconnected the neutrals from all circuits as you may have a neutral earth fault that may not be bad enough to trip it normally?

 

[Eco Deal]

get 100ma rcd been there done that or use full containment on a.c no rcd required

 

[SibertSolar]

A neutral earth fault sounds like a good shout from Screwdriver, I think. However, HF inverters do behave very similarly to TL inverters, and leakage currents do occur at very high frequencies. I reckon there's either a neutral earth fault or there's high-frequency inherent AC leakage currents being emitted by the inverter, combined with any 50Hz capacitive leakage current parasitically generated by the PV array, that are causing the "nuisance" tripping of the RCD. Solution would be to fit a 100mA trip limit instead. It's TT so you should be ok to use over 30mA, right?

Is it worth disconnecting your DC feed to the inverter before you start up, to rule out excessive capacitive leakage current being created parasitically by the PV array? Or would re-connecting the DC after the AC be a problem for the inverter? Is the array bonded and earthed?

 

[Eco Deal]

its either

100ma RCD required

Plug top wired incorrect three pin SMA plug top.

or you a.c wiring is damage (turn on A.C only see if it trips)

 

[19simon]

Went back today and fitted henley block and main switch supplementary board to test. Inverter is tripping RCD on main board still - not sure that could be. Swapped inverter for 3000HF I had in the van for next job. Works fine. I think 2500HF is faulty although I think the RCD may be faulty too.