Battery / Inverter Tripping RCD

I have had a few instances of the battery or inverter tripping out the main RCD on my consumer unit. It mainly seems to happen at the 00:30 start of a timed charge on Octopus Go, but last night happened after the battery had fully charged (I don't know exact time as I was asleep, but power was off at 06:00).

On all the previous occasions I have re-set RCD, but this morning it kept re-tripping the RCD so I isolated the PV system circuit until I was fully awake. When I switched the PV system circuit back on it has stayed working.

Has anyone had a similar problem?

Do you have 1 RCD for the entire consumer unit or is the unit split with 1 main CB and a couple of RCDs?

Do you know how old the consumer unit is and I assume you are also charging an EV at the same time as charging the battery? If so I'd expect to see around 11kw peak demand from the grid in those conditions - around 50-60A of current draw.

If it's tripping the RCDs under high load then it's likely to be a short to earth under high load conditions only, unless you have a 10kw plus electric shower it's unlikely you'll have made those sort of demands on the house circuit before.

The installer should have certified the PV, battery circuit and EV charger etc but isn't obligated to check any other aspects of your consumer unit as long as it all looks safe during install.

Can you read the Amp rating on the RCDs? They tend to be around 60A total load rating so depending again on how stuff is wired up in your consumer unit it might be exceeding that value too.

RCD trips can be caused by anything and the recent install might not even be the reason - I had a random RCB trip post PV etc install but it's got its own consumer unit - that said my existing unit was accessed. Cue lots of investigation as it was on the socket ring main (only have 1 for everything but the kitchen) and it eventually turned out to be a 1mm hole in the live insulation just touching the head of the backbox screw. It had been like that for over 2 years as I changed all the faceplates and banged out the single sockets to doubles when we moved in.

yandards Thank you for your reply.

I have 1 RCD for the whole consumer unit don't have an EV, the CU is around 16 years old and I don't have an EV as yet, the RCD is 80 amp.

I have just seen on the beta portal that I am getting a few notifications on the inverter section to check battery connection, so I am just wondering if that may be causing the problem as the tripping does seem to mainly occur during battery charging. I don't know if any of the GivEnergy (@Adam-Reynolds @Danlambert (GivEnergy)) team can let me know what the check battery connection notification may mean?

The check battery connection is the comms link between the battery and the inverter dropping out, it can be just nothing and I've had the same issue but it's not come back since the last firmware upgrade and battery recalibration.

80A should be more than enough, that said a 16 year old RCB might be passed it's best too. As I said on the previous post it might be unrelated.

I'd recommend getting in touch with your installer as its something that is happening post install and the electrician should know what they disturbed - as you have a single consumer unit they must have been in there.

Martyn
My system was installed before Christmas in a very full Consumer Unit, with one 30mA RCD looking after everything except lights. I do know (once measured with a clamp meter) there's a fair amount of earth leakage normally, but not normally a problem.
My installer found when the battery kicked in, it tripped the RCD. He temporarily switched the system to a lighting (unprotected) breaker, and will return very soon with an RCBO to fit in place of the breaker, so the system is individually protected and my safety certificate can be issued.
Hope you get it sorted!

pjb904 the 30ma is the trip detection value for current leakage, the actual trip rating will be much higher, 60 or 80A.

pjb904
My installation sounds very similar to yours (one RCD to protect all sockets and lighting circuits unprotected). Am I correct in assuming that your PV System will be left on the unprotected side of the consumer unit but as it has an RCBO it will provide the required protection?

This may be a way round the problem for me as well as it will take the PV system off of the RCD protected circuits..

Thanks
Martyn

Martyn
I can say for sure once they've been to install it. I'll let you know - they're waiting till the additional 5kW GE battery arrives (due 15th Jan) and will finish and certify the installation then.
Cheers
Paul

yandards it's the earth leakage that's causing the trip.

You can go for a type C RCBO to replace a trip switch on an RCD line. Any electrician can move the bits around and fit the RCBO.

The type C RCBO has resistance to the sudden surges that the start of charging can produce.

Martyn my installer came yesterday to easily install an RCBO to the 'unprotected' bus bar (in my case all my lighting circuits). So my solar system is now earth leakage protected, allis well, and my system can be certified and signed off.