Which heating element for towel rail?

[luca_01]

Hi,

I am going to buy two Reina Luna - in Stainless Steel, as I'd rather spend a bit more now rather than having them rusty in a few years.

First is 1500x500 and the heat output is 3544BTU / 1039W (ΔT 70°C) which converted to ΔT 50°C is 2286BTU / 670W
Second one is 720x500 and the heat output is 1935BTU / 567W (ΔT 70°C) which converted to ΔT 50°C is 1248BTU/ 366W

Now when I look at heating elements from Reina (thermostatic weekly) I see there are 300W, 600W and 900W. Which one should i be getting for each of the rail? I'd rather overkill as there is a thermostat anyway and I anticipate many towels sitting on top.

Thanks!

 

[ericmark]

1) The more towels, the less watts required. Towels insulate, stopping heat escaping.
2) The rail needs to be installed, so the water can't drain from the radiator. But failing this, the smaller the element, the more likely it is to survive.
3) Also need to ensure with element on it can't thermo-syphon and end up heating other radiators in the home, the smaller the element the less likely this will be a problem.
4) Water from towels has to go somewhere, so one needs the extractor running when towels are damp, or mould will result.

I would go for the lowest wattage, the heater is only required in the summer, and likely in summer very little is required to dry towels.

 

[luca_01]

1) The more towels, the less watts required. Towels insulate, stopping heat escaping.
2) The rail needs to be installed, so the water can't drain from the radiator. But failing this, the smaller the element, the more likely it is to survive.
3) Also need to ensure with element on it can't thermo-syphon and end up heating other radiators in the home, the smaller the element the less likely this will be a problem.
4) Water from towels has to go somewhere, so one needs the extractor running when towels are damp, or mould will result.

I would go for the lowest wattage, the heater is only required in the summer, and likely in summer very little is required to dry towels.

Sorry forgot to say. The towel radiators will be fully electric, not dual fuel. So I need the heating element to really do the work here.
I was reading "It’s generally better to choose a heating element that is just below the wattage in your towel rail. This is because towel rails and radiators have a built-in thermal fuse to stop the unit from overheating. If the element is too large, you risk tripping the fuse, which will stop the element from working."

What I don't understand is whether the 300W, 600W, 900W I see associated to the heating elements are to be compared with the watt numbers at ΔT 50°C or ΔT 70°C? Sorry I am quite confused.

 

[ericmark]

Is the towel rail to heat the room, or simply dry towels, in a room sitting at 20ºC a towel rail at 30ºC will dry the towels, so 300 watt is ample, however if heating the room then the ΔT 50°C or ΔT 70°C comes in play. So ΔT 50°C is 2286BTU / 670W means with no towels on the rail, with water at 50°C it will put 670W into the room, or in reverse one could say a element of 670 watt will heat the rail to 50°C, but with towels on the rail less energy will be required, my towel rail is in series with the hot coil in the hot water cylinder, so the boiler heat the domestic hot water first, so the towel rail is kept cooler.

A hand-held metallic part must be no hotter than 55°C and a part intended to be touched but not hand-held 70°C and a part which need
not be touched for normal operation 80°C that is regulation 423.1 from BS7671:2008 table 42.1 is seems unlikely this has changed, so I can't see why the it would quote the ΔT 70°C for a towel rail, for a simple radiator OK but can't see how one would thread towels through a towel rail without doing a bit more than just touching it, for a radiator to heat the room, one would not need to touch it.

 

[jj4091]

If it is thermostaically controlled going for the highest rated one should not make any difference as if anything trips or a fuse blows then you will obviously have a fault condition that would need to be repaired.

 

[luca_01]

If it is thermostaically controlled going for the highest rated one should not make any difference as if anything trips or a fuse blows then you will obviously have a fault condition that would need to be repaired.

Thanks. So perhaps I could stick to the 300w one for the small towel rail and go for the 900w for the big one which is 1500x500. What do you think about that?

 

[Rodders53]

I presume you do intend to have some other form of heating for the room(s) so these rails are only for towel warming/drying/hanging duties.
I replaced the (large) wet towel rails in our bathrooms with proper radiators as they were not up to the job of warming the rooms. Worse if a towel was anywhere near them.

We do also have a 500w x 800 h electric towel rail in our ensuite. It consumes 185 Watts when on (1.25 hrs am and 45 minutes pm via a smart plug/energy monitor). That gets pretty hot to the touch, although it does take some time to do so. It's adequate for what we need.
I've no idea if it was a nominally 200W or 150W element I fitted (probably around 15 years ago) but is probably a fixed 70C thermostat inside fwiw.

I see no sense in a 3x higher wattage for a 2x greater area radiator except for the speed of heating up the radiator.

NB I 'filled' my rad with water leaving a small air space. Then, once the rail was hot, I released the air under pressure via the vent, to ensure it wasn't 'under pressure' in normal use.

 

[ericmark]

Is the towel rail to heat the room, or simply dry towels,

I presume you do intend to have some other form of heating for the room(s)

Questions have been asked, no reply.

My late mother's wet room we fitted electric resistive under floor heating and a large towel rail, neither was good enough on its own to keep the room warm. The fan removed more hot air to what either of the heaters on their own could replace, but the replacement air was drawn from the hall, had the wet room been upstairs, it may have been better. The fan was switched off after the completion certificate was issued, never to be used again.

 

[luca_01]

@Rodders53 @ericmark

The two bathrooms are quite small - large one is 2.2x2 metres, small one is 2.2x0.90m. The towel radiators will be the only source of heating. There are no windows in both bathrooms, just extractor fans, it's a 70sqm flat, so it won't get much cold anyway. The towel rails are mostly for drying the towels and providing some nice comfort heat. The radiators will be fully electric and come pre-filled with oil

So the only difference in getting the 900w thermostatic element for the larger 1500x500 towel radiator would be it heats it up faster?
I've asked the retailer and they said they can do it.

My main fear is that the large towel radiator gets covered of towels and there is little heat going off for the bathroom. Would getting the 900w element instead of the 600w help in such a scenario?

Thank you very much.

 

[ericmark]

What do you use now, and how well does it work? And when the fan runs where does the replacement air come from. If the air going into the room is at 19ºC then to boost to 21ºC is not that hard, but if the room drawn from is a 17ºC then looking at double the heat rise.

 

[luca_01]

What do you use now, and how well does it work? And when the fan runs where does the replacement air come from. If the air going into the room is at 19ºC then to boost to 21ºC is not that hard, but if the room drawn from is a 17ºC then looking at double the heat rise.

Not so sure as I've just bought the flat so wasn't living there prior to the renovation works I am doing now.

So bottom line what would you say - 900 or 600w? It is going to be a thermostatic element anyway with a timer as well so perhaps I could go for the 900w element? It would just deliver the temperature I set anyway so won't make a lot of difference, I guess the only key difference would be the 900w element will be quicker in heating up the rail when I switch it on?

Thank you very much!

 

[JohnD]

The towel radiators will be the only source of heating.

900W then.

 

[Rodders53]

The most you can get out of those rads, uncovered, is the delta 50 figure.
670 W and 366 W. Except you won't want the room at 20C and rad at 70C to dissipate that heat... more like 25C for naked comfort?

Your big room might need less than 500 Watts if you plug numbers into a heat loss calculator and the small maybe only half that. To maintain a temperature once it's got there.

So the 600 and 300 options seem the closest match... probably. 900 in to a unit only capable of dissipating 670 is probably unwise and it may invoke a thermostat in the element if the fluid reaches 70C that will cut in and out rather than the room stat at the bottom of the radiator? Likely there'll be another safety cutout (non-reset) to handle the main stats failure as well. On the other hand it may all be fine in practice?

Covering them with towels will dramatically reduce the heat into the room. Trust me I have a simple double towel rail 3-400 mm above the radiator in 'my' bathroom and it makes a big difference when draped over the rad for drying cf having it folded and mostly clear. It's a north facing room similar size to your larger one and the rad type 21 rad 600x600 is 804 Watts at dT 50 but I run the CH water lower than that so the dT 30 figure of 417 W is probably closer to reality for me.

Can you fit a towel holder above to permit more warm air into the rooms rather than covering them up too much?