Towel radiator warm-up slow with electric element?

[news]

I've recently removed a small oil-filled towel radiator from my bathroom, and am replacing it with a larger one. (Old one was about 550 mm square with only 3 rails, and a 100 ish watt element, oil filled. warm-up time 20-30 minutes).

I have a white ladder style towel radiator, 377 watt rating, 1118 mm height by 450 mm wide, screwfix quote 11862. The element is a screwfix

400 watt, quote 22805. Screwfix catalogue states that this element/radiator combo is suitable.

The radiator is *not* plumbed in, as I don't have central heating (only storage heaters & fan heaters).

Presently the radiator is taking a long time to warm up - after 1 hour the top of the radiator was hot, but the bottom is still cool.

Query 1: is this long warm-up time normal or expected?

(The radiator holds about 5-6 litres water, which would take 43 - 52 minutes to heat (assuming 50 C temp rise required, 4200 specific heat capacity, no heat lost to room)

Query 2: Can I fit a 600 watt screwfix element to the radiator to decrease the warm-up time? The element is fitted with a cut-out at 70 or 80 C, so after the warmup, the radiator will maintain a steady temperature? Alternatively, could I get a larger element elsewhere? Is it safe to fit such a large element, assuming I leave an air-gap for expansion?

Query 3: could I fill the radiator with oil to reduce the warm-up time (I think Oil has a significantly lower specific heat capacity than water)? What sort of oil would be best to use? Presently the threads at the bottom of the radiator leaked with water, so these have been sealed with Plumbers' Mait. Does plumbers mait tolerate oil?

many thanks for any advice!

Richard

[David Hansen]

On 6 Nov 2006 06:50:58 -0800 someone who may be [e-mail] wrote this:-

Then it would have been better to buy an oil filled version, assuming there is an oil filled version of that model. Screwfix do several oil filled versions of some of their towel rails.

Thermostatically controlled?

From memory they do two sorts of element. One a normal one and one thermostatically controlled. The normal ones limit temperature by the discharge of energy from the rail. The thermostatically controlled ones don't, but go on and off as necessary. I assume that the inertia of the rails is enough to prevent dangerous overheating with the thermostatic elements.

It is unlikely to be safe if you use a much larger element, due to the rise in temperature. The rail may or may not burst, probably at a joint, but before then would get dangerously hot.