Placing immersion heater on standalone circuit

[Sard]

Hi,

I had a new boiler and unvented cylinder installed 2 years ago, which I recently had moved to the loft. During this job the new plumbers informed me that the previous wiring for the immersion heater was not suitable and presented a hazard and therefore left the immersion heater disconnected. Having done some research I understand that immersion heaters are best placed on their own radial circuit and whilst I won't be touching the consumer unit myself, I wanted to get an idea of whether adding a new circuit for the immersion heater was possible given my current CU? I have my floorboards up still and would like to run the cables down to the CU myself and then have an electrician come in to connect it all up for me.

Also I was thinking of adding two extra circuits to the CU, one for future loft lighting and future loft sockets. Would this be possible given my CU, in addition to the immersion heater radial? I have counted 3 vacant slots, but would like a steer here.

Many thanks in advance.

 

[JohnD]

it looks like the type of Starbreaker with the push-in tongues on the MCBs to connect to the special busbar.

IIRC the busbar can be cut to length on first installation, but you now have no space on the RCD protected side. The electrician will need to be aware of this in advance. I heard the parts are not readily available.

Find your local electrician before you start work and agree what is to be done. He will not be able to sign that he designed and installed the new circuit if he didn't. He may well agree to you running the cable if your work is visible and can be inspected (e.g. if you nail down the floorboards he wont be able to see if it has been done correctly)

 

[AndyPRK]

put a 2.5mm cable in for the immersion
out a 2.5mm cable in for loft sockets.
Adding in a new circuit for 1 or 2 loft lights is fairly pointless, unless the room is going to be used 7 days a week and has no windows.

 

[winston1]

Did the plumbers (were they sparks as well) tell you why the previous wiring was unsuitable and what the hazard was?

 

[Sard]

Did the plumbers (were they sparks as well) tell you why the previous wiring was unsuitable and what the hazard was?

Sure, they indicated that the immersion heater was not on a separate circuit and the cable from the idolater was not heat resistant. Obviously if it was just the latter, then we could have just replaced that leg. To me it looks like the isolater is spurred from an existing circuit somewhere.

 

[Sard]

it looks like the type of Starbreaker with the push-in tongues on the MCBs to connect to the special busbar.

IIRC the busbar can be cut to length on first installation, but you now have no space on the RCD protected side. The electrician will need to be aware of this in advance. I heard the parts are not readily available.

Find your local electrician before you start work and agree what is to be done. He will not be able to sign that he designed and installed the new circuit if he didn't. He may well agree to you running the cable if your work is visible and can be inspected (e.g. if you nail down the floorboards he wont be able to see if it has been done correctly)

Does it help that there's a vacant slot on the RCD side? Also I wouldn't screw down any boards until this work is done.

 

[winston1]

Sure, they indicated that the immersion heater was not on a separate circuit and the cable from the idolater was not heat resistant. Obviously if it was just the latter, then we could have just replaced that leg. To me it looks like the isolater is spurred from an existing circuit somewhere.

Although it is conventional to put an immersion heater on a separate circuit I don’t believe it is a requirement nor would I see it as a hazard not to do so. A upstairs ring is usually lightly loaded and I can’t see why an immersion cannot connect to it for instance.

 

[Sard]

Although it is conventional to put an immersion heater on a separate circuit I don’t believe it is a requirement nor would I see it as a hazard not to do so. A upstairs ring is usually lightly loaded and I can’t see why an immersion cannot connect to it for instance.

Thank you. I think for my own peace of mind, if I can have it on a standalone circuit, I'd prefer that and willing to invest time and money to have it belt & braces

 

[chivers67]

Just use the existing Upstairs lighting Radial to supply the loft lights. I think you might be able to get an RCBO (https://www.screwfix.com/p/crabtree-starbreaker-20a-30ma-sp-n-type-b-mini-rcbo/401hv think this looks correct) that is suitable for the left hand side and there is space on the right for another MCB .

 

[Sard]

Just use the existing Upstairs lighting Radial to supply the loft lights. I think you might be able to get an RCBO (https://www.screwfix.com/p/crabtree-starbreaker-20a-30ma-sp-n-type-b-mini-rcbo/401hv think this looks correct) that is suitable for the left hand side and there is space on the right for another MCB . I should think they probably didn't want the immersion fed from the RCD as they thought it might/possible nuisance trip?

Thank you, this is very helpful. In terms of adding a circuit for loft sockets, could I just wire in one socket into the loft for now and run a fused spur for the boiler from there. That should be enough to then extend the ring main fully for the loft in the future? Currently the boiler is plugged into a prexisting spur socket which I am keen to eliminate and wire the boiler properly into a fused spur on the new loft cirvuit

 

[ericmark]

The appendix to the regulations says over 2 kW fixed should have a dedicated circuit, in the main this is because near the consumer unit a heavy load can overload a ring final without opening the overload, near the centre it is not a problem, so if near centre of the ring the immersion could be supplied from the ring final, but not if near the consumer unit.

I have a feeling the RCBO may be too tall to fit? I like the immersion heater on a double pole isolator or 15 amp plug and socket (not 13A they get too hot) so if it goes faulty it is easy disconnected.

In theory any new circuit must be RCD protected, so an electrician may refuse to use the two vacant non RCD protected slots if as a suspect the RCBO is too tall. He could well say he can only use the RCD protected slot, depends on how much a jobs worth he is.

As a result get the electrician first, and see what he will let you do. In theory he could mount a second board supplied from a large MCB in that board, so there are ways around it, but I have had two fuse boxes for years with two RCD's and when I moved I decided don't want that again and loosing freezer full of food so went for all RCBO board, so let him advise you.

 

[JohnD]

think this looks correct

Edit
Having read the description, you may be right, but the picture shows a screw at the bottom, which is not right.

View media item 5161 View media item 5162

 

[chivers67]

The one i posted has a similar "tongue", I'm not 100% though?

 

[flameport]

Starbreaker ones should fit, some have a round blanking plug where the screw would be, which is probably what's in the screwfix picture.
Same plastic moulding is used the the Loadstar ones which have a screw fixing and no tab.

 

[Sard]

Thank you for all the help and input. Could someone please confirm that the CU itself is compliant or would I need to change it to a non-combustible type prior to adding a new circuit?