Just wondered if anyone has some experience here of the effect of different
wattage elements used in a towel rail?

We have an onsuite bathroom with wet underfloor heating, which is nicely
warm in the winter. Towels are hung on a multi-S shaped towel radiator,
which currently has no heat input - we just liked the shape. Towels dry
nicely in the winter, and during properly warm weather. However, in
spring/autumn when the heating is off they can seem a little damp, so I'm
intending to add an electrical element, fed from a timed spur, to the rad.

I don't have any info on the rad - special offer, no paperwork. It is multi
S shaped, with about 9 metres of 20mm pipe horizontally, and two 1.4 metre
verticals of 25mm pipe, all chromed steel.

Electric elements come from 150 watts to 600 ish. I'd like it to warm gently
for a couple of hours, rather than be hot, as no room heating is needed. I
thought 200 or 250 watts? Any experience here? Another reason for keeping
the wattage lower is that SWMBO is good at turning things on, and rather
less good at turning them off.....

Also, the rad will be filled with water, with a decent dose of inhibitor. It
will not be connected to the central heating proper. Do I get it up to full
temp to expand the water, and then close the top vent, or do I leave the
vent open a little. If closed, is an air bubble for expansion at the top a
good idea?

Thanks for ideas,

Charles F

On Sat, 23 Jun 2012 10:26:25 +0100, Charles Fearnley wrote:

I thought 200 or 250 watts? Any experience here?

Look at the spec for the raditor and find out its nominal output when used
ona CH system. Then is if 1/4 of that seems sensible?

Another reason for keeping the wattage lower is that SWMBO is good at
turning things on, and rather less good at turning them off.....

You can get "push for heat" towel rail switches that come on for a period of
time. Some allow 1/2 hour, 1hr, 2hrs.

Also, the rad will be filled with water, with a decent dose of
inhibitor. It will not be connected to the central heating proper. Do I
get it up to full temp to expand the water, and then close the top vent,
or do I leave the vent open a little. If closed, is an air bubble for
expansion at the top a good idea?

Essential, don't under estimate the strength of expansion forces. Any real
reason not to plumb it in? Water with inhibitor ought to be OK but don't seal
it straight up allow it to "breath" for a while to let the dissolved air out.
Perhaps boiled water wouldn't have much dissolved air left? Water isn't
normally used for stand alone electrically heated rails, some for of oil is
(with expansion gap). Think I'd at least look for a suitable oil rather than
use corrosive and conductive water.

--
Cheers
Dave.

On Jun 23, 10:26*am, "Charles Fearnley"
wrote:
Just wondered if anyone has some experience here of the effect of different
wattage elements used in a towel rail?

We have an onsuite bathroom with wet underfloor heating, which is nicely
warm in the winter. Towels are hung on a multi-S shaped towel radiator,
which currently has no heat input - we just liked the shape. Towels dry
nicely in the winter, and during properly warm weather. However, in
spring/autumn when the heating is off they can seem a little damp, so I'm
intending to add an electrical element, fed from a timed spur, to the rad..

I don't have any info on the rad - special offer, no paperwork. It is multi
S shaped, with about 9 metres of 20mm pipe horizontally, and two 1.4 metre
verticals of 25mm pipe, all chromed steel.

Electric elements come from 150 watts to 600 ish. I'd like it to warm gently
for a couple of hours, rather than be hot, as no room heating is needed. I
thought 200 or 250 watts? Any experience here? Another reason for keeping
the wattage lower is that SWMBO is good at turning things on, and rather
less good at turning them off.....

Also, the rad will be filled with water, with a decent dose of inhibitor. It
will not be connected to the central heating proper. Do I get it up to full
temp to expand the water, and then close the top vent, or do I leave the
vent open a little. If closed, is an air bubble for expansion at the top a
good idea?

Thanks for ideas,

Charles F

If all you want is minimum heat to aid drying a little, I'd think 150w
would get it hot and do that. If you prefer you could have a 2 heat
setting switch, one feeding 240v ac, the other via a suitably rated
diode, and use a higher power element.


NT

"NT" wrote in message
...
On Jun 23, 10:26 am, "Charles Fearnley"
wrote:
Just wondered if anyone has some experience here of the effect of
different
wattage elements used in a towel rail?

We have an onsuite bathroom with wet underfloor heating, which is nicely
warm in the winter. Towels are hung on a multi-S shaped towel radiator,
which currently has no heat input - we just liked the shape. Towels dry
nicely in the winter, and during properly warm weather. However, in
spring/autumn when the heating is off they can seem a little damp, so I'm
intending to add an electrical element, fed from a timed spur, to the rad.

I don't have any info on the rad - special offer, no paperwork. It is
multi
S shaped, with about 9 metres of 20mm pipe horizontally, and two 1.4 metre
verticals of 25mm pipe, all chromed steel.

Electric elements come from 150 watts to 600 ish. I'd like it to warm
gently
for a couple of hours, rather than be hot, as no room heating is needed. I
thought 200 or 250 watts? Any experience here? Another reason for keeping
the wattage lower is that SWMBO is good at turning things on, and rather
less good at turning them off.....

Also, the rad will be filled with water, with a decent dose of inhibitor.
It
will not be connected to the central heating proper. Do I get it up to
full
temp to expand the water, and then close the top vent, or do I leave the
vent open a little. If closed, is an air bubble for expansion at the top a
good idea?

Thanks for ideas,

Charles F

If all you want is minimum heat to aid drying a little, I'd think 150w
would get it hot and do that. If you prefer you could have a 2 heat
setting switch, one feeding 240v ac, the other via a suitably rated
diode, and use a higher power element.

The diode sounds a good idea, and yes, 150/200 watts should probably do it.

Dave L's idea of 25% of nominal output is sensible, but unfortunately when
bought as a special offer with no paperwork I don't know what that is, and
guesstimating BTU's is more difficult than with conventional radiators
because of the variation in formats.

I've seen a suggestion that leaving 10% of capacity as air will allow for
expansion, so will probably try that. I'll also investigate 3 bar safety
valves. Plumbing to the heating system isn't easy, as the bathroom was
designed for underfloor heating and pipework is now fairly inaccessible.

Thanks to both.

Charles

On Sat, 23 Jun 2012 12:41:54 +0100, "Charles Fearnley"
wrote:



I've seen a suggestion that leaving 10% of capacity as air will allow for
expansion, so will probably try that. I'll also investigate 3 bar safety
valves. Plumbing to the heating system isn't easy, as the bathroom was
designed for underfloor heating and pipework is now fairly inaccessible.

Ice at 0 deg C expands by roughly 9% over the volume of water at 4 deg
C, so if you want to allow for freezing then 10% is a good figure,
yes. Water will expand by roughly 3% between 4 deg C and 80 deg C so
if you are confident that all the temperatures are going to be
positive then 4% should do it.

http://www.simetric.co.uk/si_water.htm

Nick

On Jun 23, 1:50*pm, Nick Odell
wrote:
On Sat, 23 Jun 2012 12:41:54 +0100, "Charles Fearnley"

wrote:

I've seen a suggestion that leaving 10% of capacity as air will allow for
expansion, so will probably try that. I'll also investigate 3 bar safety
valves. Plumbing to the heating system isn't easy, as the bathroom was
designed for underfloor heating and pipework is now fairly inaccessible.

Ice at 0 deg C expands by roughly 9% over the volume of water at 4 deg
C, so if you want to allow for freezing then 10% is a good figure,
yes. Water will expand by roughly 3% between 4 deg C and 80 deg C so
if you are confident that all the temperatures are going to be
positive then 4% should do it.

http://www.simetric.co.uk/si_water.htm

Nick

A simple option is to not do the bleed valve up tight. 5% expansion
with 10% headspace = 2 atmospheres!


NT

On Sat, 23 Jun 2012 07:55:06 -0700 (PDT), NT wrote:

A simple option is to not do the bleed valve up tight. 5% expansion
with 10% headspace = 2 atmospheres!

ICBA to check the maths but two atmospheres isn't very much. Most radiators
and plumbing stuff is speced to 10 Bar, 10 atmospheres give or take a bit.
--
Cheers
Dave.

"Dave Liquorice" wrote in message
ll.co.uk...
On Sat, 23 Jun 2012 07:55:06 -0700 (PDT), NT wrote:

A simple option is to not do the bleed valve up tight. 5% expansion
with 10% headspace = 2 atmospheres!

ICBA to check the maths but two atmospheres isn't very much. Most
radiators
and plumbing stuff is speced to 10 Bar, 10 atmospheres give or take a bit.
--
Cheers
Dave.


Back of fag packet maths suggests that 10% airgap and 3% water expansion on
the 90% water will give closer to 1.5 bar at full temperature.

I've also found several suppliers of 3 bar safety valves for towel rads, so
10% airgap and a 3bar valve seems like a good combination to me.

Thanks to everyone,

Charles F