Central Heating electrical advice? DIY-able?

[chazzyB]

I had a plumber years ago in to fix a leak at the HW cylinder and he ended up replacing the whole thing.
The immersion element was moved to the new cylinder but never wired back in.
I would like get the immersion wired again and on a smart switch which I thought should be a simple DIY job but taking a look at the electrical wiring I can see why the plumber didn't want to touch it...
One 3-core bring power down into a fused switch which then enters this junction box from the rear
Two 3-core cables exit the bottom to the junction box and go up to the boiler upstairs (at least one of them does dunno what the other is)
Black cable (grey and orange cores?) goes to the motorized valve which doesn't seem to work)
White cable exits bottom left and goes to the thermostat on the cylinder
Something exits the hole in the back and goes the heating controller/timer mounted above.

So my question(s) is is this the "normal" way to hook all of this up? How would this be done properly? or is it perfectly fine?
should I just get some heat resistant 3-core and "jack" into an earth, live and neutral in this box and take it to immersion element via a smart switch?

 

[EFLImpudence]

No, the immersion needs its own supply from the consumer unit - usually 16A

Is there not one nearby that supplied the old one?

 

[chazzyB]

Nothing nearby that I can see. I expected to find one and just hook it back up.
The "consumer unit" is an old style Wylex wired fuse box with 4 circuits. upstairs and downstairs, ring and lights.
Don't know which the input on this junction box is connected to...
I'm only assuming the immersion used to be off this junction box.

 

[Sureitsoff?]

depending on how the fused switch supplying that lot has been arranged you could take the immersion feed from it instead

 

[EFLImpudence]

It won't be "off this junction box".

Was the old immersion working?

 

[chazzyB]

Don't think we ever used the immersion and the wife now thinks that it used to be on a standard 13A UK plug on a long cable that was coiled up on top of the cylinder for "emergency" hot water. Probably the plumber didn't want to put it back as it was not sufficient.

 

[chazzyB]

No, the immersion needs its own supply from the consumer unit - usually 16A

Is there not one nearby that supplied the old one?

So, while not best practice, can the immersion come "off the junction box" or is that going to be too much load on the circuit? I really don't know if anything else shares the same cable from the fuse box...
Would I be better just putting a plug/cable back on the immersion as it's only for occasional use?
I think the "correct" way forward otherwise would be getting the house rewired

 

[Murdochcat]

Do not try to connect your immersion to this wiring centre. It’s not suitable and nor will those cables take the continuous 13A load

 

[Mottie]

Our central heating is fed off the 16A spur (on its own breaker in the consumer unit) for the immersion heater. 13A fuse for the immersion, 3A for the boiler. The immersion heater will only ever be switched on if the heating packs up in which case the heating will be switched off until it is fixed. Both of them will never be on at the same time although they could be if I wanted them both on.

 

[EFLImpudence]

So, while not best practice, can the immersion come "off the junction box" or is that going to be too much load on the circuit? I really don't know if anything else shares the same cable from the fuse box...

Not from the wiring centre.
It possibly could come off the junction box supply.

It is difficult to say from the internet. Central heating is sometimes connected to a lighting circuit.

Would I be better just putting a plug/cable back on the immersion as it's only for occasional use?

You could do.
Is there a socket nearby?

I think the "correct" way forward otherwise would be getting the house rewired

It is unusual to have only the four circuits you mention in the fuse box without an immersion circuit and a cooker circuit so who knows what has been altered.


Looking back - "4 circuits. upstairs and downstairs, ring and lights".

Do you mean upstairs ring, upstairs lights, downstairs ring, downstairs lights"? That is most unusual.

 

[chazzyB]

Not from the wiring centre.
It possibly could come off the junction box supply.

by "junction box" I'm referring to the spaghetti connections box in the first picture. any other junctions are under floorboards or in walls

You could do.
Is there a socket nearby?

The CH cylinder and all these connections are in the kitchen and probably off the same downstairs ring as the 3 double sockets and single with a red "cooker" switch.

It is unusual to have only the four circuits you mention in the fuse box without an immersion circuit and a cooker circuit so who knows what has been altered.

Cooker is gas, just the clock is on electric, probably the same downstairs ring but with a separate switch

Do you mean upstairs ring, upstairs lights, downstairs ring, downstairs lights"? That is most unusual

That's exactly what I mean only 4 fuses are populated and there are 4 blanks. The labelling says Upstairs Lights, Upstairs Ring, Downstairs Light and Downstairs ring. Over the years we found a couple of exceptions so usually switch off the whole fuse box if we need to do anything like change a light switch or upgrade a socket. Yes "unusual"...

 

[ericmark]

1000's and 1000's of years ago when I was an apprentice the immersion heater would be supplied from a 15 amp plug and socket, the socket would be supplied from the blue fuse in the fuse box, there would have been 4 fuses, red 30 amp for cooker, red 30 amp for ring final, blue (15 amp) for immersion heater, and a white 5 amp for lights.

There we no electric showers, no central heating, no RCD protection, and a card of spare fuse wire.

The plumber would not touch electrics, and the electrician did not touch plumbing so the 15 amp plug and socket was ideal.

But as time moves on we want more electrics, so using what did feed the immersion to feed something else like the boiler was common.

The 13 amp socket needs a plug with a fuse, and a fuse works by melting, so they get hot, so running 3 kW for a short time like a kettle OK but for a long time the fuse will make the plug hot, and it needs to be in free air to cool, or in a large lump like a fused connection unit (FCU) to dissipate the heat. The 15 amp plug did not have a fuse.

As time has gone on we have included more safety items, and split the supply into more than 4 circuits, my house has 14 RCBO's the rules today require RCD protection and the MCB replaced the fuse and the RCBO replaces the MCB and RCD. There is nothing to say the home needs upgrading, but anything new has to follow the new rules. So you can have old sockets not RCD protected but not new, so the first new socket after 2008 can cost a fortune as fuse box needs to be changed to a consumer unit with RCD protection.

I now use an immersion heater, only because I have solar panels, cheaper to heat before that with oil, so not used, emergency only.

So is it worth it? I would say forget the immersion heater, whole house needs RCD protection, I have one circuit not protected, the boiler, because it has battery back up. But that's up to you.

 

[RandomGrinch]

So my question(s) is is this the "normal" way to hook all of this up? How would this be done properly? or is it perfectly fine?

Just for clarity, what hasn't been mentioned directly yet - your system is "normal".

In a system like yours, the hot water is primarily heated by the boiler, as gas is cheaper than electricity; the immersion element is usually only used as a backup.

This means that the boiler electrics are a separate entity - your 'junction box' is a wiring centre to control and supply the low current zone valves, thermostats and any pump associated with the boiler.

As has been stated above, an immersion heater should ideally have its own circuit, and shouldn't be connected to the wiring centre.

 

[chazzyB]

1000's and 1000's of years ago when I was an apprentice the immersion heater would be supplied from a 15 amp plug and socket, the socket would be supplied from the blue fuse in the fuse box, there would have been 4 fuses, red 30 amp for cooker, red 30 amp for ring final, blue (15 amp) for immersion heater, and a white 5 amp for lights.

Well I have 2 white and 2 red fuses only, the red ones being on upstairs ringmain and downstairs ringmain. The heating used run off oil, but was converted to gas sometime (at least 25 yrs ago) which I guess is when the immersion was added.
I just looked at the fusebox labels again and it says "Downstairs Ringmain and Gas H."

 

[chazzyB]

Just for clarity, what hasn't been mentioned directly yet - your system is "normal".

In a system like yours, the hot water is primarily heated by the boiler, as gas is cheaper than electricity; the immersion element is usually only used as a backup.

Thanks, might be the "old" normal, but good to know it is some kind of "normal" . The only reason I even thought about using the immersion is because we are on Octopus agile, and sometimes it would be cheaper to heat the water on electric and we have no backup if anything happened to the gas system.

As has been stated above, an immersion heater should ideally have its own circuit, and shouldn't be connected to the wiring centre.

As "own circuit" would effectively mean a rewire (unless it's an easy job to run new cable from the fuse box) I think we will have to weigh up if it is worth it.
.