What size RCD should be fitted for inverter?

Hi folks,
I've had my inverter RCD trip twice now in last two months..few folks have suggested earth leakage or water ingress, first time was after a really dry spell of weather and we had rain..second was today when we were actually away. Our RCd is 30amp I think. The other thing is we have the EPs socket wired up and running the router/modem off this..it had it's on 10amp RCD which didn't trip either time the inverter tripped. Anyway I've seen some people say replace the RCD with a higher rated one but I don't want to do that to mask the issue.

Cheers
Mick

Think it's max 32 amp for 5.0 hybrid inverter?

michaelmcgoldrick do you mean 30mA for the RCD, as opposed to a 32A MCB? Two very different things, get in touch with a qualified electrician to do this type of work.

stevelewis yep I've notified the installer.

Is your inverter outside?

If so, is there a canopy or similar over it?

we had an intermittent fault on our system with RCD tripping. extremely frustrating as there seemed no rhyme or reason. Meant system was sometimes off for some time if I did not endlessly check. Ended up taking the front off the Consumer Unit just to help make it more obvious! When it tripped the EM115 would be off and unlit so was much more visible - especially as CU is not hidden in a cupboard - in our utility room.

Installer came several times. even removed each solar panel to check connections (luckily single storey and flat roof). Could not resolve.

Finally resolved when "normal" electrician in the house for other work and he suggested replacing RCD. Since then no trips at all!

RCDs can be extremely (over) sensitive and can fail... An RCD which is continually tripping may already be faulty or low-quality to begin with but either way repeated tripping can cause the RCD to deteriorate over time.

I had PVs, inverter and battery installed in Oct 2022 and fed from RCD controlled consumer unit. No issues in 4 months.
Fitted the EPS circuit up in Feb and straight away had numerous RCD trips on unchanged electrical system in house.
Ended up taking main RCD out and using MCB, but fitting individual RCBOs to the outgoing circuits to give each of them RCB protection. No more trips.
My inverter and battery are in bone dry loft.

would be nice if @Givenergy had an alert for failures such as trip? in theory should be relatively easy to see from the data

SteveCook Ended up taking main RCD out and using MCB, but fitting individual RCBOs to the outgoing circuits to give each of them RCB protection. No more trips.

Sorry "each of them RCD protection". Typo

SteveCook out inverter is inside.. we also had eps fitted in May.. but it wasnt until we had a lot of rain after a prolonged dry spell that we had our first trip.. we had another yesterday while away.. we are running the modem/router/tv/sat box - from the eps (its in ups mode)

we have a 10 amp rcbo fitted between the eps socket and the inverter and this doesnt trip. It was tested by the electrician who fitted and it trips when it should. Ive notified our installer of the solar panels/inverter so will be interested to see what they do.

fwiw our intermittent tripping was also noticeably more likely to happen after rain and/or when we washed the panels. It was one of the reasons the installer removed all panels to check connections.

But as mentioned the resolution was actually a replacement RCD even though original one appeared ok

Tim Adams thanks this is the rcd fitted.

our RCD for inverter, EM115 & solar is a completely separate CU - also Hager
not sure if any advantage but there was no space in existing CU anyway

interestingly i spoke to my installer and the person i deal with is out of office today - but they have had a fair few reports of inverters tripping over the last few weeks. They going to organise someone to take a look

michaelmcgoldrick
Is it the inverters tripping or the RCDs feeding the inverters

For me it's the rcbo on the consumer board that's tripping

I think that ABB RCBO is a type AC.
I think you should have a type A.
NB I am not an electrician, just reading guidance on the web and manufacturers literature

Not related to this but I have queried the new gateways use of type AC RCDs for AIO and seperate PV inputs.
Awaiting feedback on that.

hoggy

Interesting, that would be sub optimal if it was indeed incorrect.

The fact it’s not perfectly integrated and a bit built up is however good as you can replace parts if needed.

michaelmcgoldrick

I have whole house EPS on manual Changeover.

My inverter is fed from its own mini consumer unit.

I have an issue when we simulate a grid failure, on grid return the inverter RCD trips.

My installer has the same issue at another property. He's unable to get to the bottom of why. Tried replacing RCDs for bigger etc no joy.

I've got a suspicion it's something to do with the EPS to grid Changeover in the Inverter as there is a small delay from when the grid comes back to the RCD tripping. But it's way above my head.

Waterski99
Agree 100% and that is why I took the main RCD out of the board and replaced with MCB and then protected all the other circuits (other than inverter) individually with RCBOs to give each of them earth leakage protection.

RCD tripping is probably earth leakage trip and not a fault current.

Domestic UK RCDs are all 30mA (I think) earth leakage. Increasing the overload current rating will not fix the earth leakage issue.

SteveCook so instead of an rcbo you can put an MCB for the inverter power supply and then a rcbo on the eps circuit from the inverter? what size mcb did you fit?

I can't say if my MCBs would be the same size as you should have, but both inverter and EPS are 32A in the consumer unit, but EPS circuit also has local MCB adjacent to inverter at 10A to limit draw exceeding EPS output as GE literature.
Outgoing ways from main consumer unit and EPS consumer unit are now individual RCBOs (for most, not smoke heads and burglar alarm as these dont want nuisance trips)