Correct way to install a plug socket off this fused connection unit?

Participant · 16 Feb 2025 at 12:24

Hi all

I want to put a plug socket in my airing cupboard next to this FCU (which switches the boiler). It'll be for a cordless vacuum cleaner.

Is it safe / correct to just take a spur off that grey cable before the FCU? Or should I take from the switched output?

Thanks.

ZG002 · 16 Feb 2025 at 15:33

Neither without more info.

Do you know where the spur is fed from? A socket circuit? It's own circuit? It's hard to tell from the photo but what size is the cable feeling it? (The grey cable)

Participant · 16 Feb 2025 at 16:45

ZG002 said:
Neither without more info.

Do you know where the spur is fed from? A socket circuit? It's own circuit? It's hard to tell from the photo but what size is the cable feeling it? (The grey cable)

Thanks, I think it's 2.5mm T&E but I don't know what fuse is in there and what circuit it's on. Will check.

LuckyBenski · 17 Feb 2025 at 22:27

Important details are whether that is just the 2-pole switch for isolating the boiler (required), or it's a spur off another circuit and that's the FCU required (as well as meeting the isolator requirement).

And as mentioned the size of the cable.

sx_turbo · 17 Feb 2025 at 22:38

You can put something like this in

Buy a twin patress box, use your existing fcu and add single socket next to it

Axiom Pattress Box

A strong and sturdy dual pattress box for use with two single sockets or switches. This 32mm back box from Axiom is robust, reliable and easy to work with - it comes in a classic white finish to blend in with any home interior.• 2 gang dual pattress box with a depth of 32mm• Knockout on the side...

www.toolstation.com

For a cordless vacuum the load would be a few amps, they have a low voltage charger similar sort of amperage to a mobile phone.

Mercenary Keyboard Warrior · 17 Feb 2025 at 23:07

I assume the FCU is simply being used as a switch.
The point of an FCU being to protect the cable itself so wouldn't be any use at the end of the spur.

Do you have any other FCUs that could be protecting the cable.

Actual I guess everyone is assuming ring main, could you be radial?

But that could be a botch and not really taking mains there directly.
Best to spend some time looking to try to work out where the other end of that cable goes.

Pop the nearest sockets off and see if you can detect it coming from them.

If your happy its really mains and you think suitable I would add a FCU from that one, drop it to 3amp and then a socket by the side of it.
That way if anyone did try to plug something high draw in it would blow the fuse.
Maybe put a sticker saying 3A only on it.
Vax for example charges at 1.5Amp

Dg834man · 18 Feb 2025 at 13:38

If its a spur off a ring you could fit a double socket and stick a plug on the boiler cable with a appropriate fuse.

LuckyBenski · 18 Feb 2025 at 13:45

Dg834man said:
If its a spur off a ring you could fit a double socket and stick a plug on the boiler cable with a appropriate fuse.

And ensure it's a double pole isolating socket.

Participant · 18 Feb 2025 at 16:57

Hi all. Here are some more pics and answers to some of the questions above:

The supply cable is 2.5mm^2 T&E:

The cable goes under the floor so I can't trace it:

Here's the fuse board; they're all RCD protected but I'm not sure which circuit the boiler is on?! Should I switch each off so I can figure it out?

The FCU is fused at 3A:

Not sure where to go from here.

200sols · 18 Feb 2025 at 17:33

2.5mm suggests its just a spur on the socket circuit.

You can just wire in a single socket to the load side of the FCU and retain the 3amp fuse. Obviously the issue with things like this is people forget and plug in a high power item.

Alternatively fit a new 13a fcu on the supply and feed both the boiler fcu and a new socket from that. Just check it's on the socket circuit.

ZG002 · 19 Feb 2025 at 07:13

Turn off the "old immersion heater" mcb and see if it goes off, I'd check the "water heater" mcb next.

I'm assuming you have a combi boiler in the cupboard now? If so they have likely used one of those circuits.

If it goes off with either of them two then you are pretty much good to go, I'd add in a single socket before the fcu. They are 16a supply's on 2.5mm and also 30mA RCD protected. (Just re-mark the board when done to boiler & socket)