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

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

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

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.

Query 2: Can I fit a 600 watt screwfix element to the radiator to
decrease the warm-up time?

Thermostatically controlled?

The element is fitted with a cut-out at 70
or 80 C, so after the warmup, the radiator will maintain a steady
temperature?

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.

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?

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.



--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54