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Gents, after a bit of a sanity check before i dig out my toolbox.

My Synsynk AC system has been tripping its RCBO a few times of late and cutting the AC to the invertor, three times this morning after rain showers, happens generally on wet days.

I've been doing a bit of research/Watching excitable Keith @ Synsynk training videos etc and appreciate that the likely issue is culmulative earth leakage of the house in total being picked up by the RCBO due (according to Keith my Synsynk invertor adds a little of this itself). So im working on the premise that some of my weather affectable external wiring, to my external sockets/shed/tortoise/pond etc is a tad iffy, and to be honest although it has worked fine for years some of it is not my finest of work. I will replace it all shortly once weather improves.

In the meantime i am wondering whether removing the 20a 30mA RCBO and replacing with it with an 16/20a MCB is an alternative for the time being? I would also like to remove the currently fitted Surge Protection Device (none of my other CU's have these) and replace that with a 63a 30mA RCD at the same time as the new MCB.

From what i understand (my invertors AC wiring is surface mounted and approx 6m long) all that is required is an MCB under the regulations, although i would want the protection an RCD offers even if not strictly required (if im correct?), seems silly not to.

Would appreciate your critique as to my thoughts on the CU alterations.
Fully Appreciate i could get a sparks to carry out housewide Earth leakage tests to try and ID any source before doing anything but i am currently mired in so much that it will be tricky to organise quickly, so would be far quicker for me to change the CU arrangement, after isolating the external 'iffy' circuits one by one.

What type is the rcbo?

AGT wrote: ↑Sun Jan 26, 2025 2:15 pm What type is the rcbo?

Rcbo is a Fusebox made (based in Kilmarnock) Rtam b20 type, assume thats a B type model

resybaby wrote: ↑Sun Jan 26, 2025 2:38 pm

AGT wrote: ↑Sun Jan 26, 2025 2:15 pm What type is the rcbo?

Rcbo is a Fusebox made (based in Kilmarnock) Rtam b20 type, assume thats a B type model

Blimey this is confusing. Code numbers on the rcbo would suggest a type B. However when looking on the manufacturers website it would appear that the B labelled rcbo is a type A (mines circled on the attached photo) Thanks for the document AGT, shall give that a good read.

resybaby wrote: ↑Sun Jan 26, 2025 1:24 pm Gents, after a bit of a sanity check before i dig out my toolbox.

My Synsynk AC system has been tripping its RCBO a few times of late and cutting the AC to the invertor, three times this morning after rain showers, happens generally on wet days.

I've been doing a bit of research/Watching excitable Keith @ Synsynk training videos etc and appreciate that the likely issue is culmulative earth leakage of the house in total being picked up by the RCBO due (according to Keith my Synsynk invertor adds a little of this itself). So im working on the premise that some of my weather affectable external wiring, to my external sockets/shed/tortoise/pond etc is a tad iffy, and to be honest although it has worked fine for years some of it is not my finest of work. I will replace it all shortly once weather improves.

What sort of inverter is it? Is it a battery inverter with an ac out and an ac in? Does the 'iffy' wiring connect to the ac out?

Or

Is it a battery / pv / hybrid inverter that is 'ac coupled' to the rest of the house, meaning it's only connection to everything ac is via the rcbo?

In the meantime i am wondering whether removing the 20a 30mA RCBO and replacing with it with an 16/20a MCB is an alternative for the time being? I would also like to remove the currently fitted Surge Protection Device (none of my other CU's have these) and replace that with a 63a 30mA RCD at the same time as the new MCB.

From what i understand (my invertors AC wiring is surface mounted and approx 6m long) all that is required is an MCB under the regulations, although i would want the protection an RCD offers even if not strictly required (if im correct?), seems silly not to.

Replacing the 30mA rcbo with an mcb, and replacing the main switch with a 30mA rcd won't solve the problem of nuisance tripping as you'll be activating the same function in a different breaker.

Does the inverter installation guide recommend the use of a 30ma rcd? The inverter should be installed as per the manufacturer's instructions to be compliant.

Not sure why you want to get rid of the spd?

(Looks like type A rcbo to me)

Thanks for the reply Marcus.

Its a Sunsynk ecco hydrid with batteries and ac coupled, so yes all current via the rdbo.

The iffy wiring is just a cheap waterproof external socket kit from Screwfix bolted to the rear of the house and fed via fused spur from the house sockets ring main. The shed/pond/tortoise is simply fed from that external socket via some 2.5mm Twin and earth i had lying around installed through my log store, which then supplies a triple socket in the shed, and onto the pond/tortoise via domestic plugs. Its certainly not installed to part p or anything, im kind of assuming the external socket may be letting water in given the issue only occurs after heavy rain, and everything else is under cover.

Not thinking of removing the main 100a switch, just adding an Rcd in place of the spd (i understand these 'wear out' in a few years and i dont want to leave the wife with that headache in the future).

Further reading suggests a type A rcbo, which after double checking mine it appears to be, despite the misleading part number, isnt ideal for PV. Perhaps i should start there first

Manufacturer advises RCD to be used

AGT wrote: ↑Sun Jan 26, 2025 4:40 pm Manufacturer advises RCD to be used

Beat me to it AGT, thank you.
Id sooner have one in there anyway tbf.

From the document I posted earlier
Regulation 551.7.1 of BS 7671:2018+A2:2022 provides requirements where a generating set may operate in parallel with the distribution network, such as a PV system. It states that where an RCD is providing additional protection in accordance with Regulation 415.1 for a circuit connecting the generator set to the installation, the RCD shall disconnect all live conductors, including the neutral conductor. This can be in the form of a double-pole or single-pole with switched neutral protective device. It is important to check as some compact RCBOs are only available as single-pole devices. This requirement has been included in BS 7671:2008.

It is important to select the correct type of RCD according to DC residual current to prevent the RCD being blinded. Regulation 712.531.3.5.1 of BS 7671:2018+A2:2022 provides requirements for RCDs for solar photovoltaic (PV) power supply systems. It states that where an RCD is used for protection of the PV AC supply circuit, the RCD shall be of Type B according to BS EN 62423 or BS EN 60947-2, unless the inverter or installation provides at least simple separation between the AC and DC side or the inverter does not require a Type B RCD as stated by the manufacturer, based on their instructions.