Retrofit 2nd RCD

[Seb101]

this is my current CU layout

It’s split load with the RCD protecting the three high amp MCBs on the right.

On the non-RCD side there are 4 lighting circuits, plus one for burglar alarm and one for boiler.

If I wanted to RCD protect the left side of this would it be within regs to wire two of the lighting circuits through a single MCB to create enough space for a second RCD? Provided it is correctly labelled etc.

I have fitted LEDs throughout, even every light in the house on at the same time would not be more than 2A plus a couple of extractor fans... well within limits.

 

[JohnW2]

On the non-RCD side there are 4 lighting circuits, plus one for burglar alarm and one for boiler. ... If I wanted to RCD protect the left side of this would it be within regs to wire two of the lighting circuits through a single MCB to create enough space for a second RCD? Provided it is correctly labelled etc.

Four lighting circuits is a bit of overkill (for an 'ordinary house'), so I can't see anyone complaining about your reducing that to three, or even two. The burglar alarm could probably be run off one of the lighting circuits (or a sockets circuit via FCU), and even the boiler could probably be run via an FCU from a sockets circuits. You therefore have the potential to lose up to 4 of those MCBs.

I suspect that at least some people would regard what you are proposing as being notifiable work.

Kind Regards, John

 

[Seb101]

Oh and before anyone comments- the supply was off that the main isolator in the meter cupboard when that photo was taken!

 

[EFLImpudence]

Is it worth doing?

 

[Seb101]

Four lighting circuits is a bit of overkill (for an 'ordinary house'), so I can't see anyone complaining about your reducing that to three, or even two. The burglar alarm could probably be run off one of the lighting circuits (or a sockets circuit via FCU), and even the boiler could probably be run via an FCU from a sockets circuits. You therefore have the potential to lose up to 4 of those MCBs.

I suspect that at least some people would regard what you are proposing as being notifiable work.

Kind Regards, John

That’s what I thought, 4 is overkill. So there is no silly rule like there can only be one radial ‘circuit’ per MCB or anything like that?

 

[Seb101]

Is it worth doing?

It follows on from my post about the metal stud work the other day. You can pick up the Memshield 2 80A/30mA RCD modules for about £15 so it seems minimal outlay for peace of mind.

 

[JohnW2]

That’s what I thought, 4 is overkill. So there is no silly rule like there can only be one radial ‘circuit’ per MCB or anything like that?

Nope - a radial circuit can 'branch' anywhere, including at the MCB. Indeed, even for a ring circuit one can take a spur from the MCB.

Kind Regards, John

 

[Iggifer]

The only problem with trying to add a second RCD to that board is the way the factory connections are done. They're solid copper links from the main switch to the non-rcd neutral terminal. You'd need to get that out and then get some tri-rated (usually 16mm²) singles and take one from the main switch to the RCD and one from the RCD to the main switch. Then you'd need some brown to feed the RCD from the main switch.

The real issue is getting them all into the bottom of the main switch, shouldn't be an issue I would imagine it can take two 16mm² cables but you'd need to make sure you got a good grip on both of them

 

[Seb101]

The only problem with trying to add a second RCD to that board is the way the factory connections are done. They're solid copper links from the main switch to the non-rcd neutral terminal. You'd need to get that out and then get some tri-rated (usually 16mm²) singles and take one from the main switch to the RCD and one from the RCD to the main switch. Then you'd need some brown to feed the RCD from the main switch.

The real issue is getting them all into the bottom of the main switch, shouldn't be an issue I would imagine it can take two 16mm² cables but you'd need to make sure you got a good grip on both of them

Yes I see what you mean. Should be no problem getting two 16mm2 cables into the main switch but getting the bus bar link out of the bottom of the main switch is going to be the challenge.