Heated towel rail element wiring/socket

[MisterProzilla]

Hi,

I've recently refurbished the bathroom and thought I might as well put in a heating element for drying towels in the summer while I was on. Now wiring it up is one of the last few things left to do and I'm not 100% sure how to do it.

Is there any guidance on what type of fitting is best - I understand a plug socket needs to be 3m away from any water outlet, and it's only a 2.4m long room, so that's not an option. Does this also apply to things like fused wall plates without an open socket? And is there any specific back box I would need to use? I'm guessing a plastic one would be advisable, but not sure what the options are for the front plate and what's recommended for heated elements.
For reference:
- It's a Terma Moa element, which has controls and a preset 2-hour mode on the element itself so I wasn't planning on a fancy timer socket or anything like that.
- The wall box is about a foot above the element/rad valves, around half a foot away to the side, and it's approx 2-3ft away from the toilet.

I screwed an old plastic back-box to the wall before it was plastered just so I had the placement, and there's a length of twin/earth running down from the attic behind the plasterboard into the back of the box, so I think I'm ready to just wire up the fitting in the bathroom then wire up the other end to mains in the attic when ready.


Any advice would be appreciated!

Thanks everyone

[ericmark]

The 3 meter rule does not apply to fused connection units.

[Neelix]

It’s 2.5 meters now

Does your circuit have rcd protection ?

[ericmark]

There is no real problem using a fused connection unit (FCU) it is only plug and socket which is a problem. The biggest problem with towel rail is will it thermo-syphon and heat up other radiators or DHW.

[MisterProzilla]

It’s 2.5 meters now

Does your circuit have rcd protection ?

I have no idea! Is there an easy way to tell? The fuseboard seems fairly new - would rcd be built into the board or is it an extra device attached nearby?

[MisterProzilla]

There is no real problem using a fused connection unit (FCU) it is only plug and socket which is a problem. The biggest problem with towel rail is will it thermo-syphon and heat up other radiators or DHW.

I've heard it recommended that you close one rad valve before turning it on, would that solve the problem? Thermo-syphoning is a new one to me - is it a big issue?

[ericmark]

This may help working out if RCD protected

PartID_CU.jpg (41.37 KiB) Viewed 1227 times

note RCD/RCBO has test buttons. As to thermo syphon I got caught out, basic idea is water over 4 degs C expands when heated so becomes less dense, so a fire with back boiler down stairs could heat the DHW upstairs without any pump.

Early central heating used the same idea, and having the pump and boiler running did central heating, but just the boiler would heat just the DHW, however I found the boiler if switched on without the pump would do as designed on only heat the DHW, but if the pump ran for even a short time, once the water has started to flow, it continued to flow.

The normal way was to have the towel rail connected to the DHW, so even in the summer, the towel rail is heated, but with the advent of the combi boiler, the DHW is no longer circulated, so we get immersion heaters in the towel rails. In the main there is no problem, but if the CH fires up or even just the pump when some anti stick software exercises it, it can start the thermo syphon running. Less likely with micro bore, and normally some needs to kick off the thermo syphon running, as as long as not used 24/7 each time it turns off, and thermo syphon is stopped.

I would just monitor what happens, may well not be a problem, but be aware it can happen, but a combined FCU and timer as often used for immersion heaters for DHW seems order of the day, or night, don't want a sweltering hot bathroom in the summer, my towel rail is heated with the DHW which is heated in summer 4 times a week half hour each time the boiler turns on, for me this is enough to also dry the towels on the towel rail. I set the time over night, as don't want to heat a house which is already hot with the sun. Seems odd saying that today, when 10 degs outside, but in hight of summer have needed to run the AC for around 10 days a year, so very aware of problems getting house too warm.

[MisterProzilla]

Ah great, I'll have a look tonight and see if I can spot those modules. To be honest I think I'll be better off just getting an electrician to do the majority of it once I've done the easy stuff - a towel rail and extractor fan need installing, which is going to require a bit of electrical work in the attic, and I'd like them to have a look at putting the attic wiring on a different circuit.

Thanks for the info re: the towel rail. Re-read it twice but still don't understand most of it we have a combi boiler, the pipe across the whole CH system is 15mm so not micro-bore. I would only be using the towel rail element in the summer, turning on either manually or with the 2-hour mode, when there's no chance of the CH coming on ... are there any symptoms I should look out for? Or can I safely bury my head in the sand and hope nothing explodes?

[ericmark]

You will likely have no problem, but the feed pipes should remain cool, if one feed pipe heats up then you are likely getting thermo syphon, but with a combi boiler it is unlikely.