• Looking for a smarter way to manage your heating this winter? We’ve been testing the new Aqara Radiator Thermostat W600 to see how quiet, accurate and easy it is to use around the home. Click here read our review.

Double Socket with FCU For Boiler? Recommendations Please

Joined
10 Nov 2025
Messages
2
Reaction score
0
Country
United Kingdom
Hi
When we had our heating installed 10 years ago, the guy just put a plug on the boiler and plugged it into a double socket in our kitchen.
I was never happy with this, and now want to replace the double socket.

Is there a double socket sized faceplate I can get that would allow 2 sockets and also include an FCU to wire the boiler in?

I have looked but want to make sure I'm getting something suitable.
 
When we had our heating installed 10 years ago, the guy just put a plug on the boiler and plugged it into a double socket in our kitchen.
I was never happy with this, and now want to replace the double socket.
Nothing wrong with that - better in some respects when unplugged.

Is there a double socket sized faceplate I can get that would allow 2 sockets and also include an FCU to wire the boiler in?
Not sure I understand the question.

You can get dual back boxes which allow fitting of one single socket and one FCU.
 
I'm hoping I could do it all in one unit, so have 2 usable plug sockets, and an FCU switch for the boiler?

The main benefit would be gaining a plug socket, but also having the boiler on its own FCU felt better to me.

What would you say is better about having the boiler on a plug?
 
or triple back boxes , i have used for a doublke socket and FCU if required
But that would mean , taking out the old backbox and remaking the hole in wall
maybe just take off the cover plate and put a single backbox next to it and wire the fused FCU as a spur - depends on what you have already in that socket

i have always had boilers on a plug, as i just prefer it that way - no reason just peronal preference

maybe a photo of the wires in the back of that double socket
 
I'm hoping I could do it all in one unit, so have 2 usable plug sockets, and an FCU switch for the boiler?
No.

The main benefit would be gaining a plug socket, but also having the boiler on its own FCU felt better to me.
You can always add sockets.

What would you say is better about having the boiler on a plug?
Pulling out the plug is complete disconnection/isolation - better than switching off an FCU.
 
I can't understand why one would use a FCU? OK, now my central heating is battery backed anyway, but until it was, being able to plug it into my jump start unit if we had a power cut (300 watt output) Battery pack and charger.jpg seemed a good idea. So much messing around with a FCU, only reason to use one, is when that supply is not from a RCD.

Triple sockets have been around for years
1762779414159.png
normally all three on one 13 amp fuse in the socket, some even fit in a double back box. Note the fixing screws on this one
1762779576104.png
but is a bit thicker.
 
Boilers require Double Pole isolation so must be used with a plug and an UNSWITCHED socket, or with a FCU.

Plugging into a switched socket is not permitted, as not all switched sockets are DP switched.

This might be in Gas Safety regs rather than Electrical regs, but is required.
 
Boilers require Double Pole isolation
Unless all lives are switched off, it is not isolation, there is a list, table 53.2 in the old BS7671:2008 not sure what it is in the latest edition, there are three classes, Isolation, Emergency Switching, and Functional Switching, the switched FCU is permitted for emergency switching, where the unswitched FCU, and sockets be they switched or not, are not permitted for emergency switching, but the plug lock
1762821756341.png
clearly isolated both lives, the line and neutral, but the FCU only switching the line by putting a lock through the fuse carrier, it needs the switch locking off to isolate. However, the main point is supply type, with TN-C-S it may be permitted only to switch the line, but with a TT supply both line and neutral need switching, so the best way to ensure isolation not just functional switching is to use a plug and socket.

The only reason why my boiler is on a FCU is the supply is not RCD protected, it is a balance, if RCD protected then a small leakage could stop the heating running, but if I was to use a non-static emergency supply, Back-up-power.jpg then there is no RCD protection anyway. Only with the static back-up is there an earth rod, and the neutral is connected to earth during a power outage.

I still feel a plug and socket is a more positive isolation method, and it allows the easy use of an alternative supply, as to if the 300 watt from the unit I have shown would be enough to run a boiler I don't know.

As to gas regulations, can't see these being in conflict with electrical regulations. There are strict rules about switching the protective device, these may have changed due to charging of EV's outside the equal potential zone, but I know many boiler instructions do allow either plug and socket or FCU, I think the leaning towards the FCU is to stop the boiler from being unplugged.
 
but also having the boiler on its own FCU felt better to me
A plug is a fused connection device. There is no practical difference to using what you're thinking of as an FCU, regardless of how you feel (sorry), and there are likely plenty of other heat-making devices in your home that are plugged in, probably in such a manner that the plug never leaves the socket; ovens, hobs, fan heaters, kettles, hair dryers, toasters, plasma TVs etc may all use fused plugs that are seldom/never removed

The boiler will be a very low draw device, and as such if you need more plugs, a multi plug block that allows you to plug two devices in where the boiler is will let you connect the other appliance you're considering locating near the boiler's present socket

Consider too if you have sockets that permanently have a wall wart phone charger plugged into them, that it's possible to get sockets that have USB outlets which will free up some 3 pin points when you move/remove the wall warts
 
Last edited:
Many boiler manufacturers state the use of non switched socket
They also say it needs a type A RCD and many other things, and in general with manufacturer instructions it seems they just cut-and-paste lumps, I have had battery devices with instructions on how to fit a plug.

In the main regulations tell us to fit switches to sockets, with larger capacity types, often interlinked, so one can't fit or remove the plug without it being switched off first. So that instruction seems very dated, as that is not what is considered good practice today.
 

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.


Are you a trade or supplier? You can create your listing free at DIYnot Local

 
Back
Top