Should/shouldn't an inverter be connected via an RCD?

[ChrisJEvans]

Should/shouldn't an inverter be connected via an RCD?
On line I'm finding conflicting advice.

I have two spare slots on my consumer unit (which has an RCD on both splits) do I get the electrician to add a 32Amp circuit breaker to the consumer unit for the inverter or connect via standalone circuit breaker to a Henly block.

proposed setup:
15 x panels (Sitting in my garage) JA SOLAR 385W Mono Half Cell Black Frame W/B (JAM60S20MR BF)
6k inverter (as soon as I can find one in stock/on reasonable delivery time!)
Batteries: Probably 2 x Pylontech US2000C
iBoost

[Oldgreybeard]

Yes, must have RCD protection, as it's a metal cased bit of kit that is not double insulated. The RCD should be be a Type A, and not a Type AC.

[Stinsy]

It is nothing to do with the inverter and everything to do with the cable.

If: clipped direct, more than 50mm beneath the finished surface, or physically protected (SWA or steel conduit/trunking), then no RCD is required.

[Oldgreybeard]

It is nothing to do with the inverter and everything to do with the cable.

If: clipped direct, more than 50mm beneath the finished surface, or physically protected (SWA or steel conduit/trunking), then no RCD is required.

Not true unless the inverter is double insulated, I'm afraid. All non-double insulated bits of installed kit must have RCD protection now, been the case for some time I believe. The risk is from exposed conductive parts that may well become live if there is a fault. The RCD will detect the small electric shock or leakage current and prevent a serious shock from someone touching the metal case during a fault.

[Stinsy]

It is nothing to do with the inverter and everything to do with the cable.

If: clipped direct, more than 50mm beneath the finished surface, or physically protected (SWA or steel conduit/trunking), then no RCD is required.

Not true unless the inverter is double insulated, I'm afraid. All non-double insulated bits of installed kit must have RCD protection now, been the case for some time I believe. The risk is from exposed conductive parts that may well become live if there is a fault. The RCD will detect the small electric shock or leakage current and prevent a serious shock from someone touching the metal case during a fault.

Do you recall which reg says that? Because it is contrary to my understanding (unless you mean specific to TT installations)!

[Oldgreybeard]

Part of Sections 400 to 415 I believe, may have changed numbering with the new regs, my copy is a few years out of date. General rule is that anything fixed with exposed conductive parts has to be wired via an RCD protected circuit. I had this out with the MCS chap that installed our system, as at the time the house wasn't completed and we were still running from the TBS. The TBS was, like all of them, TT, and the only thing wired in the house was a small CU for a couple of sockets and a spare way to temporarily connect the PV system. There was only an MCB in there, and the chap had to go out and get an RCBO replacement, as the 100mA RCD in the TBS didn't meet the requirement for 30mA protection.

To be fair I should really have fitted a 30mA RCD in the mini CU, but I was re-using an old garage one as it was only going to be temporary.

It's possible that the regs have relaxed since I bought my copy in 2011, though. I have a suspicion the RCD requirement may also be in the installation instructions for the inverter. I'll dig them out and see. makes sense to RCD protect an inverter even if there is a way to wriggle out of it, though. I'd rather any bit of metal I might touch had RCD protection, no matter what the regs say, TBH.

[Marcus]

Think I'm with stinsy on this one.

If it's TT, you need an RCD.
If the cabling is not protected by earthed armour or otherwise protected you need an RCD .
If the equipment installation instructions say it needs an RCD (they probably do) it needs an RCD.

If it's class 1 (i.e. not double insulated class 2) it must be earthed.

Chances are, you probably need an RCD anyway, so just put one in (type a).

[AGT]

Follow the manufacturer’s instructions..

[Oldgreybeard]

Always fitting the right type of RCD protection gets my vote, as already mentioned.

Just tried to copy the relevant bit from my (old'ish) copy of the On Site Guide. Inverters are not specifically mentioned, all the Guide gives is this, which could be interpreted as meaning an RCD isn't needed. I've just pulled the instructions out for my inverter and they do say that the supply must have double pole RCD protection to at least Type A, though. I would guess that if the manufacturer states something then that clinches it as far as it being a requirement.

RCDs.jpg (171.18 KiB) Viewed 1070 times

[Marcus]

To answer your original question:

The RCDs in you cu are probably type AC, and i would be reluctant to put a solar inverter on a 'split' RCD with other circuits anyway as the inverter could increase the risk on nuisance tripping.

So (with the usual caveat that i haven't seen your system so cannot be sure), i would either shuffle you existing RCDs, MCBs along and put an RCBO type a in next to the master switch, or put in into it's own c.u. connected via Henley blocks, whichever works best for you.