Heated Towel Rail Element: What Rating?

[macman81]

I need to replace a heated towel rail element that has failed. It's rated at 600W. However, there's another towel rail in the house which is probably at least 2/3 of the size, yet that one is only 250W.
So, how do you select the correct rating? On the rail size, or the room size? I'm thinking maybe use a 450W one as a compromise, but is there any more scientific way of calculating it?

 

[morqthana]

If you get a thermostatic one, or have a thermostatic control, a more powerful one will more often be up to the job at any time.

 

[Taylortwocities]

The bigger the radiator, the bigger the element will need to be. You need to give us a bit more info.

 

[morqthana]

There's usually a range of sizes which will physically fit. I would always prefer to use the largest which will go in.

It can be instructive if you can find a wet towel rail of the same size, or close, to see what the output is.

 

[macman81]

I've calculated the wattage required based on the bathroom size, (6.5 sq m) and it comes in at just over 600W. So it seems like the original element was about right.
Yes, I am going to fit a Tesla TCP200 control panel so that it can be set to give a 2 hour heating cycle, rather than controlling it manually.

 

[Taylortwocities]

Ah. There’s a difference between using a towel rail for its original purpose of drying your towels, and using it to heat a whole room!
You’ll notice that room radiators have profiles that boost the heat (hence the term ”radiator”). So your calculations will be widely different for a towel rail versus a proper radiator.

 

[ericmark]

I do not know how much energy is required to heat 15 litres per second of air from zero to 20ºC, it does not matter the size of the bathroom, the extractor fan will move that amount.

But where the air comes from will change what is required, from a bedroom it may be at 20ºC to start with, but from the hall could be 10ºC, and from outside down to zero.

The whole idea of a room 6 x 6 needing x watt/hour does not work, I installed under floor heating, good job also a towel rail, as even at 27ºC the maximum surface temperature for tiles, it would not maintain the wet room temperature at 20ºC when it was drawing replacement air from the hall.

Use a heat recovery unit instead of an extractor fan, and then a whole different ball game. Also using inferred that does not heat the air, and I have not talked about double glazing or cavity wall insulation.

Best is x watts was not enough so increase, or x watts got the room too warm so it can be reduced.