Combined RCD / FCU - alternative to MK?
Combined RCD / FCU - alternative to MK?
Author
Discussion

Scarletpimpofnel

Original Poster:

1,362 posts

40 months

I'm looking for a combined RCD/FCU to add as a spur to an internal ring main socket to provide power outside.

I like MK stuff but their device is £70 ish - MK Logic K385WHI 1 Gang 13A RCD Connection Unit Passive

I can see other RCD/FCU on eBay for £20 ish .... but unbranded and untrusted by me.

Anyone know a good cheaper alternative to MK?

tia

finlo

4,137 posts

225 months

Scarletpimpofnel said:
I'm looking for a combined RCD/FCU to add as a spur to an internal ring main socket to provide power outside.

I like MK stuff but their device is £70 ish - MK Logic K385WHI 1 Gang 13A RCD Connection Unit Passive

I can see other RCD/FCU on eBay for £20 ish .... but unbranded and untrusted by me.

Anyone know a good cheaper alternative to MK?

tia
It would be cheaper to fit an RCD to the whole installation (assuming it doesn't already have one).

OutInTheShed

12,804 posts

48 months

The stuff at Toolstation is OK, BG a bit nicer than Axiom and so on.

I think there can be an advantage in not having a singe whole-house RCD, like some outdoor light or whatever not taking out the freezer.

finlo

4,137 posts

225 months

OutInTheShed said:
The stuff at Toolstation is OK, BG a bit nicer than Axiom and so on.

I think there can be an advantage in not having a singe whole-house RCD, like some outdoor light or whatever not taking out the freezer.
If it has a main RCD it will likely trip as well as the secondary one.

Scarletpimpofnel

Original Poster:

1,362 posts

40 months

To be fair the CU already has a 30mA RCD but it's an old installation so I was thinking belt and braces getting a new decent RCD/FCU in line with the outside socket. But if it's not necessary then I won't waste my money. I will simply add a FCU (13Amp) as a spur from an existing inside socket to feed the outdoors socket.

Open to other ideas?

Thanks all.

netherfield

3,017 posts

206 months

DorsetSparky

562 posts

32 months

Scarletpimpofnel said:
To be fair the CU already has a 30mA RCD but it's an old installation so I was thinking belt and braces getting a new decent RCD/FCU in line with the outside socket. But if it's not necessary then I won't waste my money. I will simply add a FCU (13Amp) as a spur from an existing inside socket to feed the outdoors socket.

Open to other ideas?

Thanks all.
There's no reason to have more than one 30mA RCD on a circuit, furthermore it's poor practice, as there's no rhyme or reason to which one will trip first apart from sensitivity. It's not 'belt and braces', it's not the right thing to do. If the current one trips correctly, then that's fine.
Just put the outside socket on a switched fused spur as you've higlighted.

Scarletpimpofnel

Original Poster:

1,362 posts

40 months

DorsetSparky said:
Scarletpimpofnel said:
To be fair the CU already has a 30mA RCD but it's an old installation so I was thinking belt and braces getting a new decent RCD/FCU in line with the outside socket. But if it's not necessary then I won't waste my money. I will simply add a FCU (13Amp) as a spur from an existing inside socket to feed the outdoors socket.

Open to other ideas?

Thanks all.
There's no reason to have more than one 30mA RCD on a circuit, furthermore it's poor practice, as there's no rhyme or reason to which one will trip first apart from sensitivity. It's not 'belt and braces', it's not the right thing to do. If the current one trips correctly, then that's fine.
Just put the outside socket on a switched fused spur as you've higlighted.
Got the message thanks :-) I'll skip adding a further RCD. Thanks all.

OutInTheShed

12,804 posts

48 months

DorsetSparky said:
There's no reason to have more than one 30mA RCD on a circuit, furthermore it's poor practice, as there's no rhyme or reason to which one will trip first apart from sensitivity. It's not 'belt and braces', it's not the right thing to do. If the current one trips correctly, then that's fine.
Just put the outside socket on a switched fused spur as you've higlighted.
That's fair comment up to a point, but if I plug my RCD extension lead into my socket fed by a RCBO-protected ring main, when I press the test button on the extension lead, it's the extension lead's breaker that trips 10 out of 10 tries!
I'm quitting while I'm ahead and not pushing the button again!

Can you easily buy an RCD that's spec'd to break before the RCBO or whole-house breaker?

finlo

4,137 posts

225 months

Pressing the button is a physical test I don't think it creates a fault that the main RCD can see.

Belle427

11,174 posts

255 months

Tuesday
quotequote all
As above.
Probably a good idea to use a portable one on gardening tools but is it such a problem if you do chop the lead and the main house RCD goes?
It can be a good idea to have an internal isolation point though for any external sockets, lights etc in the event of a fault so they can be quickly eliminated.

OutInTheShed

12,804 posts

48 months

Tuesday
quotequote all

You're right, pressing the test button creates an imbalance which trips the plug-in breaker but the RCBO back in the board doesn't see any imbalance, so won't trip.

Some years ago though, when working on mains powered stuff in a lab, we used to test with resistor to earth, it was always the bench breaker that tripped and not the RCD back at the consumer unit.

You don't always want to plunge people into darkness, lose their data etc. At home, it can be a pest if you interrupt the cooker or dishwasher halfway through.

Of course it's best not to be having mains fault events, but some thought about the consequences of everything tripping might be worthwhile.