Undertile electric heating... On walls?

[Seri]

I'm about to start with revamping the bathroom and am going to be putting in undertile electric heating.

The bathroom has three exterior walls, and although I've had thermal board put up before being plastered it still gets quite cold in winter so I want to make sure the heating system can make it nice and toastie.

This issue I have is that the floor space in the bathroom is limited, so, I was wondering if there's any issue with putting the loose wire type heating system on the walls as well before tiling them? I was only considering going up to about 2.5 feet from the ground.

Any reason why this is a bad idea? I can't find anything on google about it...

Thanks

[David WE Roberts]

"Seri" <saln...@gmail.com> wrote in message
news:1441136.265.1330517403569.JavaMail.geo-discussion-forums@vbux23...

**********************

Possibly contravenes electrical regulations about only running wires in
certain well known places?

--
No plan survives contact with the enemy.
[Not even bunny]

Helmuth von Moltke the Elder

(\__/)
(='.'=)
(")_(")

[Andy Burns]

David WE Roberts wrote:

> "Seri" <saln...@gmail.com> wrote:
>
> I was wondering if there's any issue with putting the loose wire
> type heating system on the walls as well before tiling them?

Certainly sounds unconventional, have you estimated the cost per day to
run it?

> Possibly contravenes electrical regulations about only running wires in
> certain well known places?

Does underfloor itself count as a safe zone? Isn't the heating wire
over-wound by two layers of CPC, does that count for the purposes of
BS8436? somehow I doubt it ...

[harryagain]

"Seri" <saln...@gmail.com> wrote in message
news:1441136.265.1330517403569.JavaMail.geo-discussion-forums@vbux23...

Underfloor heating is best suited to rooms in continuous occupation.
You're probably better off with some sort of radiant heater.

[NT]

Theres nothing about having it on a tiled wall that's any worse than
having it in a tiled floor, so yes it would work. TBH though its
usually better to spend the money on insulation so you dont need more
heat. Is cavity filling an option? (its diyable) The other thing is
that if you'r heating the wall up, you'll lose more heat, as happens
with UFH, so just like UFH you should have some pretty thick
insulation in place. Is there really no cheaper heating source there
than electricity?


NT

[js.b1]

Electric underfloor heating is rarely a viable due to small free space
in a bathroom :-)

#1 - Insulate the walls to 40-60mm Marmox (there are cheaper clones).
The transformation is simply enormous - because instead of trying to
heat the walls & tiles you only need heat the air in the small room,
which is must faster & much easier. Internal insulation has a *very*
substantial effect.

#2 - Avoid tiling on the floor, consider a warmer wet room vinyl
surface like Alto Marine (it is not expensive).

If heating by electric...
Set the towel rail element to provide a low background temperature,
which is boosted on demand. This can be done manually by a 600 Watt
MEG element on a 1200x550 WHITE towel rail; you set it to 30-37.5-45oC
for most of the time and only push the buttons to make it run 60oC for
the periods when it is very cold.

If heating by water...
Fit a double radiator or such like to boost performance.

HOWEVER, a bathroom conversion from "no insulation to 40mm Marmox"
needs very little heating. As you put thick marmox up you suddenly...
become aware... the cold is going... and you are getting piggin hot...
even when you were shivering before with freezing brickwork in front
of you. Just from your body heat. Quite surreal and catches you out
when plastering or tiling because things... suddenly... begin to go
off very very quickly if thermally activated :-)

The vinyl wet room systems are superior to tiling - you can get non-
slip tiles, but vinyl feels warmer and done properly it is the
solution of choice from hotels to NHS to disabled. Forget underfloor
heating, insulate heavily + towel rail or proper radiator.

[Seri]

JS, thanks for the really helpful reply, it's much appreciated.

The bathroom has just been plastered, thermal plasterboard was put on all the exterior walls first and it has made a heck of a difference.

Why specifically a white heated towel warmer over a chrome one?

[js.b1]

On Feb 29, 9:24 pm, Seri <salnaj...@gmail.com> wrote:
> The bathroom has just been plastered, thermal plasterboard
> was put on all the exterior walls first and it has made a heck of a difference.

It will - particularly when you heat it because a lot less heat is
needed.

> Why specifically a white heated towel warmer over a chrome one?

Chrome towel rails have 20% less output than white because the heat is
reflected back inside at the chrome interface.

So a 550x1200 towel rail may be 600 watts (or equiv in BTU) in White,
but only 500W in Chrome. So you would need (say) 550x1400 in Chrome to
get the same heat output as 550x1200 in White.

If you have bought an underfloor electric heating kit they sell fine
on Ebay, but for small bathrooms there is just too little space as a
rule.

Since you have insulated things are so much better - I found 200 watts
was sufficient for a bathroom which calculations before insulating
needed 654 watt. That is in part because a) some insulation was added
and b) the house heat merely "topped up" the heating as the door was
opening - it had to take the room AIR from 15oC to 18oC which it did
"in a minute".

I recall 650 Watts will heat 7.5m^3 of AIR from 0oC to 20oC in under 8
minutes. You can only achieve that with internal insulation, on the
inside of walls, but it gives very rapid response for rarely used
rooms. You then just set background heating to hold the room at "not
below 10-12oC" which does not cost much even electrically.

MEG elements remember the last setting (eg, 45oC) even if power
removed (ie, used on a timer). Some other towel rail elements hold a
low background temperature, then boost up for 1-2-3-4hrs as necessary
or via timer trigger. Those fancier elements get expensive, nothing to
stop someone fitting TWO towel rail elements in ONE towel rail - eg,
two 300W MEG elements in a 600W rated white towel rail, one being on
24/7 and the other coming on via timer to boost things up (as a
colleague does).

[Rod Speed]

js.b1 wrote
> Seri <salnaj...@gmail.com> wrote

>> Why specifically a white heated towel warmer over a chrome one?

> Chrome towel rails have 20% less output than white because
> the heat is reflected back inside at the chrome interface.

Nope, there is only one place the electrical energy can go with both types.

> So a 550x1200 towel rail may be 600 watts (or equiv in BTU) in White,
> but only 500W in Chrome. So you would need (say) 550x1400 in Chrome to
> get the same heat output as 550x1200 in White.

Nope, there is only one place the electrical energy can go with both types.

[js.b1]

On Feb 29, 10:40 pm, "Rod Speed" <rod.speed....@gmail.com> wrote:
> js.b1 wrote
> > Seri <salnaj...@gmail.com> wrote
> >> Why specifically a white heated towel warmer over a chrome one?
> > Chrome towel rails have 20% less output than white because
> > the heat is reflected back inside at the chrome interface.
>
> Nope, there is only one place the electrical energy can go with both types.

A white towel rail has a higher BTU than a chrome towel rail. Full
stop.

Electrical energy is converted into heat, it must travel through the
structure of the towel rail and be convected (& to some degree
radiated). Towel rail elements work to a thermostatic temperature,
fixed elements to 65-70-75oC & thermostatic elements to 30-60-70oC.
The ability of a chrome plated towel rail to lose heat is lower than
that for a white towel rail, its BTU rating is less.


As a safety note, towel rail elements should also have a safety
thermostatic typically at 95-98oC. Unfortunately if the thermostat
either fails or is not present it is possible for a water/coolant
filled electric towel rail to overpressure and become a bomb. Fitting
a 3 bar pressure relief valve is advisable when running electric-only
with water/coolant, mineral oil avoids this problem (it will just get
damn hot). NWT on Ebay & Online carry the 1/2" BSP PRV safety valve
for about £7.99-11.99. Not cheap, but useful from a safety
perspective. Likewise they should not be filled to 100%, but an air
gap to allow for expansion of water during heating.

Branded elements usually have 2 stages of thermostat with the second
safety 95-98oC trip being a non-resetting fuse.

Note the PRV has a push-down top (spring loaded at 3-bar), if you turn
the towel rail upside down this top is pushed in by the weight of the
towel rail. I have a distinct suspicion that will be unpopular if it
dumps mineral oil or water/coolant mix all over the floor. Car coolant
or (better) Fernox is necessary for anti-corrosion of usually rusty
(!) towel rails.

Towel rails do not give their rated BTU output when covered with
towels... this can lead to some (cold) surprises in newly fitted
bathrooms and why oversizing by about 200W is not a bad idea.

If a proper radiator can be fitted, or 2kW IPx4 downflow fan heater,
things are warm much quicker - the towel rail then becomes a mere
"towel warmer" which is frankly a better use than "room heating
radiator".

[Rod Speed]

js.b1 wrote

> Rod Speed <rod.speed....@gmail.com> wrote
>> js.b1 wrote
>>> Seri <salnaj...@gmail.com> wrote

>>>> Why specifically a white heated towel warmer over a chrome one?

>>> Chrome towel rails have 20% less output than white because
>>> the heat is reflected back inside at the chrome interface.

>> Nope, there is only one place the electrical energy can go with both types.

> A white towel rail has a higher BTU than a chrome towel rail.

You cant actually explain where the energy ends up with a chrome rail.

> Full stop.

Fraid not.

> Electrical energy is converted into heat,

Yes, and that can only end up in one place, in that bathroom with
both configs, idenditcal in all respects except the type of rail surface.

> it must travel through the structure of the towel rail
> and be convected (& to some degree radiated).

Yes.

> Towel rail elements work to a thermostatic temperature,
> fixed elements to 65-70-75oC & thermostatic elements
> to 30-60-70oC. The ability of a chrome plated towel rail
> to lose heat is lower than that for a white towel rail,

Not with a fixed element it isnt.

> its BTU rating is less.

The amount of heat is entirely determined
by the electical load with a fixed element.

> As a safety note, towel rail elements should also
> have a safety thermostatic typically at 95-98oC.

Thats an entirely different matter to what happens in normal use.

None of the rest below has anything to do with what is being discussed.

[Jeremy Nicoll - news posts]

Seri <saln...@gmail.com> wrote:

> I'm about to start with revamping the bathroom and am going to be putting
> in undertile electric heating.
>
> The bathroom has three exterior walls, and although I've had thermal board
> put up before being plastered it still gets quite cold in winter so I want
> to make sure the heating system can make it nice and toastie.
>
> This issue I have is that the floor space in the bathroom is limited, so,
> I was wondering if there's any issue with putting the loose wire type
> heating system on the walls as well before tiling them? I was only
> considering going up to about 2.5 feet from the ground.

Call me a luddite, but I am not keen on putting anything behind or under
tiles; if it goes wrong it's going to be expensive and messy to get at.

I quite like the Glen-Dimplex downflow fan heaters for bathrooms; a little
noisy perhaps but they push quite a lot of warm air out fairly fast and have
a thermostatic cut-out which stops them once the room temp has been raised.
They're easy to fit, and easy to get at if there's a problem with them.
They make air circulate in the room which is good for ventilation, and
drying the room afer a shower (I do have a decent fan as well) and if
someone is having sickness/diaorrhea in the middle of the night and has a
fit of the shivers the heater can help a lot. That's especially true if the
heater is sited close to the loo.

There is one issue with them - the pull-cord fastens inside the heater to a
plastic rocking lever. When the end with the cord is pulled down the other
end of the rocker moves up and presses against a microswitch. The amount of
travel required is small. I have found my aged mother can't understand that
pulling hard on the cord isn't needed, so - so far - she's managed to break
two of the plastic levers.

Mum thinks it's a design fault though I'm less sure - if the lever didn't
break then all that pulling could break the switch off the PCB or even break
the PCB... Part of mum's problem is psychological - the heater comes with a
cord with a tiny lightweight plastic blob on the end, but she's changed it
to a heavy metal teardrop which looks as if it will need a strong pull. It
also means the teardrop's weight is permanently holding the microswitch end
of the plastic lever against the microswitch which reduces the needed travel
even more.

She has another of these heaters in a utility room. There, since the
pullcord from the heater would have been in an inconvenient place I put a
separate much more robust ceiling-mounted pull switch in near the door, and
that's surviving just fine.

--
Jeremy C B Nicoll - my opinions are my own.

Email sent to my from-address will be deleted. Instead, please reply
to newsre...@wingsandbeaks.org.uk replacing "aaa" by "284".

[gri...@gmail.com]

On Thu, 1 Mar 2012 11:17:24 +1100, "Rod Speed"
<rod.sp...@gmail.com> wrote:

>>> Nope, there is only one place the electrical energy can go with both types.
>
>> A white towel rail has a higher BTU than a chrome towel rail.
>
>You cant actually explain where the energy ends up with a chrome rail.

It can't magic itself away, so if the chrome or paint finish is
affecting the effectiveness adversely, the 'stat would kick in and cut
the power, so the element wouldn't be heating the rail to full extent.

[Rod Speed]

gri...@gmail.com wrote

Pity there is no thermostat with fixed rails.

[gri...@gmail.com]

On Sat, 3 Mar 2012 09:59:24 +1100, "Rod Speed"
<rod.sp...@gmail.com> wrote:

>> It can't magic itself away, so if the chrome or paint finish is
>> affecting the effectiveness adversely, the 'stat would kick in and cut
>> the power, so the element wouldn't be heating the rail to full extent.
>
>Pity there is no thermostat with fixed rails.

I've never seen an electrically heated rail with no 'stat.

[Rod Speed]

gri...@gmail.com wrote

You're talking about the safety cutout, not the thermostat.

[Tim Watts]

Then it gets hotter until the emitted power balances the input power.
--
Tim Watts

[Rod Speed]

Tim Watts wrote

And so there is no difference between a chrome and white rail.

Essentially because the electrical power has to end up somewhere, the same place in both cases.

[Tim Watts]

Yes - even if the surface had an emissivity of 0 (super polished silver is
around 0.02), it would just get hot enough until convection and conduction
sorted the balance out :)

--
Tim Watts

[js.b1]

On Mar 3, 12:46 am, "Rod Speed" <rod.speed....@gmail.com> wrote:
> You're talking about the safety cutout, not the thermostat.

Evidentally Rod Speed lives in a different world.

Very old elements had a single cutout, which was not meant to operate
routinely hence early failure if fitted to an undersized towel rail
(or one regularly smothered in towels). They would be prone to extreme
temperatures once covered in towels, creating burns, and therefore
unfit for purpose and safe usage. I doubt anyone in the UK has sold
these for a decade if not longer, but the USA may well still do so
despite liability. The towel rail or radiator would not have to be
sized just to the element, but sized according to the likely number of
towels - so would be cold until covered (insulated) allowing
temperatures to rise. Alternatively a LOW wattage element could be
used which by size can never cause a high temperature situation to
occur; the legal onus would be on any installer to ensure an excessive
temperature can never occur. Oddly enough, we now move onto the real
world type...

Modern elements comprise two types; conventional element 65-75oC fixed
stat with 95-98oC safety non-resetting cutout; PTC element which is
self limiting and 95-98oC safety non-resetting cutout. The former will
cycle as necessary (they are audible in many cases), the latter will
simply maintain the design temperature. This is true even if they are
covered in towels to avoid severe temperature, both rely on sensing
water temperature.
Hence white towel rails or radiators have a higher BTU & Watts rating
than chrome, or stainless, or black, or anthracite. If you still doubt
this I suggest you go around any UK website, they make it clear.

[Rod Speed]

js.b1 wrote

> Rod Speed <rod.speed....@gmail.com> wrote

>> You're talking about the safety cutout, not the thermostat.

> Evidentally Rod Speed lives in a different world.

We'll see...

> Very old elements had a single cutout, which was not meant to operate
> routinely hence early failure if fitted to an undersized towel rail
> (or one regularly smothered in towels). They would be prone to extreme
> temperatures once covered in towels, creating burns, and therefore
> unfit for purpose and safe usage. I doubt anyone in the UK has sold
> these for a decade if not longer, but the USA may well still do so
> despite liability. The towel rail or radiator would not have to be
> sized just to the element, but sized according to the likely number of
> towels - so would be cold until covered (insulated) allowing
> temperatures to rise. Alternatively a LOW wattage element could be
> used which by size can never cause a high temperature situation to
> occur; the legal onus would be on any installer to ensure an excessive
> temperature can never occur. Oddly enough, we now move onto the real
> world type...

> Modern elements comprise two types; conventional element 65-75oC fixed
> stat with 95-98oC safety non-resetting cutout; PTC element which is
> self limiting and 95-98oC safety non-resetting cutout. The former will
> cycle as necessary (they are audible in many cases), the latter will
> simply maintain the design temperature. This is true even if they are
> covered in towels to avoid severe temperature, both rely on sensing
> water temperature.

> Hence white towel rails or radiators have a higher BTU & Watts rating
> than chrome, or stainless, or black, or anthracite. If you still doubt
> this I suggest you go around any UK website, they make it clear.

Now you have a problem with explaining why the thermostat
doesnt produce the same result with white and chrome rails
when it measures the temperature of the surface of the rail.

[js.b1]

The thermostat measures FLUID TEMPERATURE INSIDE THE RAIL, and NOT the
surface of the rail.

Since a chrome radiator is LESS effective at convecting heat due to
the insulating layer this causes the fluid inside the radiator to be
warmer than it would be in a white radiator, so triggering the
thermostat sooner than a white radiator would

Hence the the BTU / Watts for White towel rails is higher than for
Chrome. Find one that is not.

The real world difference is small.
Some white radiators are as little as 7% higher BTU & Watts then their
chrome counterparts, most around 16%. With a 500W element that is 80W
(an incandescent light bulb worth), with a 1000W element it is 160W
more.

If stuck for Watts, go for white, go wider not just taller.
Using underfloor heating, which is limited to 100-150W per square
metre, is not going to work on small UK bathrooms.

Another poster commented on downflow fan heaters.
The key thing to note is downflow fan heaters are rapid bathroom
warmup, towel rails & underfloor heating are 1hr warmup time (Marmox
insulation under floor). So a towel rail can be relegated to being
small and drying towels with say a MEG 200W or 300W set to 45oC (3rd
LED of the 5 LEDs).

[Rod Speed]

You'v dismantled every single one eh ? Yeah, right.

> Since a chrome radiator is LESS effective
> at convecting heat due to the insulating layer

There is no 'insulating layer'

> this causes the fluid inside the radiator to be warmer
> than it would be in a white radiator, so triggering the
> thermostat sooner than a white radiator would

Dont believe it.

> Hence the the BTU / Watts for White towel rails
> is higher than for Chrome. Find one that is not.

> The real world difference is small.

Bet its actually microscopic if it even happens at all.

> Some white radiators are as little as 7% higher BTU &
> Watts then their chrome counterparts, most around 16%.

That assumes that the thermostats have identical real setpoints. You cant assume that.

> With a 500W element that is 80W (an incandescent
> light bulb worth), with a 1000W element it is 160W more.

> If stuck for Watts, go for white, go wider not just taller.
> Using underfloor heating, which is limited to 100-150W per
> square metre, is not going to work on small UK bathrooms.

Makes a lot more sense to use hot air or radiant heaters instead.

> Another poster commented on downflow fan heaters.
> The key thing to note is downflow fan heaters are rapid bathroom
> warmup, towel rails & underfloor heating are 1hr warmup time (Marmox
> insulation under floor). So a towel rail can be relegated to being small
> and drying towels with say a MEG 200W or 300W set to 45oC (3rd
> LED of the 5 LEDs).

And the color of the rail doesnt matter because you can change the set point.