Towel rail too hot

[rreanor]

I've just replaced my towel rail element, as the one that was there before was only 100w, and it never got above luke warm.

I put in a 400w one (https://www.screwfix.com/p/flomasta-towel-radiator-heating-element-white-400w/245tf) , but this is so hot you can barely touch the towel rail.

Should the rail be this hot? The rail itself is 500x1000.

If not, how am i supposed to know which element it requires? I dont want to get a thermostat controlled one, as these are expensive, and i thought the whole point of an element was to reach a specific temperature.

 

[EFLImpudence]

, but this is so hot you can barely touch the towel rail.

Should the rail be this hot?

Well, I suppose it begs the question "How hot is this hot?" but - generally, yes.

It wouldn't be much use otherwise as you have found.

 

[foxhole]

I've just replaced my towel rail element, as the one that was there before was only 100w, and it never got above luke warm.

I put in a 400w one (https://www.screwfix.com/p/flomasta-towel-radiator-heating-element-white-400w/245tf) , but this is so hot you can barely touch the towel rail.

Should the rail be this hot? The rail itself is 500x1000.

If not, how am i supposed to know which element it requires? I dont want to get a thermostat controlled one, as these are expensive, and i thought the whole point of an element was to reach a specific temperature.

I always fit to timer control switch so it cycles on and off during day and off overnight to minimise cost .

 

[Jackrae]

Next best guess 200watt

 

[flameport]

, and i thought the whole point of an element was to reach a specific temperature

A heating element provides heat energy the whole time it's turned on.
In a radiator, it will only stop increasing in temperature once the heat losses from the radiator are equal to the heat input from the element.
The only way to change that is to install a thermostat which switches the element off when a certain temperature is reached.

 

[ericmark]

I am trying to work out how a towel rail can not be thermostaticly controlled, they are designed to be covered, with towels, so not safe without some thermostatic control.

I use a boiler to heat domestic hot water with no thermostat on the tank, but there is one on the boiler.

 

[JohnD]

I am trying to work out how a towel rail can not be thermostaticly controlled, they are designed to be covered, with towels, so not safe without some thermostatic control.

Agreed

And a room stat would not be suitable because the insulating layer of towels will stop the heat getting out.

400W is not much, but at this time of year it is more than you need, especially if it is permanently on.

Depending how well insulated the bathroom is, it might not be enough to keep it warm in cold weather. My bathroom is very well insulated and has a 500W, but with TRV, which is fine. It was not enough before the CWI went in.

One option would be to change the FCU for a timed controller, so it would turn off after half an hour or an hour.

 

[ericmark]

There are loads of timers, but timers rated for bathroom use is not so easy, I have wondered if I will now need something to heat towel rail in the summer, winter heated with central heating, and I did use boiler to heat domestic hot water which would also heat towel rail in summer, but now use an immersion heater connected to solar panels in summer, but never really had a problem with damp towels.

If towels are damp, then room must be damp, so any device used in the room would need a suitable IP rating, and needs to be hard wired type, so not sure what would be suitable for a damp bathroom?

 

[blup]

400w is clearly too much for that level of heat.

Blup

 

[Rodders53]

Well a certain Victoria Plumbing supply a 300 Watt element with a towel rail kit of that size, for what that is worth.
Flomasta quote a 299 Watt output rating for that size in their range at deltaT 50.

I expect even the simplest heaters must have a built in thermostat, just to limit the temperature of the fluid in the towel rail? This place https://www.electricradiatorsdirect.co.uk/news/a-guide-to-our-towel-rail-heating-elements/ reckons 65 C --- which would suggest a bit hotter than that at the top when the fluid at the bottom element reaches that 65 C point via thermal convection.
It is a potential burns risk (as are all CH radiators where the circulating water is around that temperature).

FWIW I have my towel rail on an energy monitor smart switch (cable fed through the wall of the ensuite from the bedroom). The radiator gets very hot to the touch after an hour or so on. On for 2.5 hours total a day it uses 426 Wh -- so must be 150 Watts. It is also a fair bit smaller in dimensions perhaps only 400w x 700h. A separate radiator warms the room during the cold seasons.

 

[EFLImpudence]

As I mentioned in my reply; we don't know how hot "too hot" is.

I remember a thread where someone said his HW cylinder thermostat was set to 60º but the water still got too hot to wash your hands.

 

[securespark]

But that's because our body temperature is around 37 degrees....

 

[Adam_151]

I always understood the rough guide was if you can hold onto it/touch it for a reasonable amount of time (suppose >5s) then its likely <50C, if you move away in discomfort or pain then its above that. Obviously individuals vary, but on average, and likely applies to healthy adults only. I seem to remember hearing it in relation to heatsinks on computer processors ~20years ago

 

[ebee]

Well I would think you always need some way of regulating heat to within a safe level.
Ideally a thermostat in many instances.
If the architecture of an assembly and the situation it is used in will always ensure excess above this level will dissipate then fair enough but otherwise some kind of stat type system must be used especially with something intended to deliberately add heat as part of its basic function

 

[ericmark]

As I mentioned in my reply; we don't know how hot "too hot" is.

I remember a thread where someone said his HW cylinder thermostat was set to 60º but the water still got too hot to wash your hands.

From table 42.1 A part intended to be touched but not hand-held metallic 70°C. A part which need not be touched for normal operation metallic 80°C but I would say a radiator could reach 80°C but you need to touch a towel rail to put towels on/off it so 70°C.

However I fail to see how one can ensure this with simple time, as how many towels and how thick the towels are would change the temperature, and clearly if the water was to boil, there is also a danger with pressure, in the same way as we are forced to have a cut out on the immersion heater the same must also apply to a towel rail.

Yes a simmer-stat in suitable box, could control the temperature, but then we get into type testing, and what is safe for use in a bathroom, I did look at a thermostatic version it was £40 so £17 more, but can't see how one would fit on my towel rail, it comes down to far, I suppose at 100 watt it is unlikely to get that hot, but at 400 watt that is the size of the heater I used to keep my caravan warm, I used time for my domestic hot water, and there all timers designed for an immersion heater

but that costs £20 so more than a proper element with thermostat.