We've just had an extension built and we specified wet underfloor
heating for it (by Osma/Wavin). The plumber's installed it, the
manifold gets warm, as do the flow and return pipes, but they're not
nearly as hot as the rads, and I can barely detect any heat emerging
from the floor at all even if I turn the wall thermostat up to 25C.
I've never seen the ambient temp in the room go higher than 17C even
with the boiler temp full blast at about 80C.

On top of the heating boards is 17mm plywood, some thin underlay
(recommended by the manufacturers for UFH) and then B&Q click-to-fit
wooden boards (also said on the pack that they would be OK for UFH).

We've got a beefy combi boiler (15 lit/m) and the rest of the heating
in the house is fine. I balanced the rads a couple of weeks ago to see
if that might help, but it didn't.

The plumber says it's working, and that UFH is just "very subtle." I
agree there is some heat going into the floor, and I realise the floor
won't be as hot as a radiator or anything, but I was expecting at
least *discernible* heat from the floor when walking on it in bare
feet. Is that not the case?

If anyone has any tips, I'd be grateful. I know next to nothing about
plumbing though.

On Jan 9, 3:46*pm, BlueJohn wrote:
We've just had an extension built and we specified wet underfloor
heating for it (by Osma/Wavin). The plumber's installed it, the
manifold gets warm, as do the flow and return pipes, but they're not
nearly as hot as the rads, and I can barely detect any heat emerging
from the floor at all even if I turn the wall thermostat up to 25C.
I've never seen the ambient temp in the room go higher than 17C even
with the boiler temp full blast at about 80C.

On top of the heating boards is 17mm plywood, some thin underlay
(recommended by the manufacturers for UFH) and then B&Q click-to-fit
wooden boards (also said on the pack that they would be OK for UFH).

We've got a beefy combi boiler (15 lit/m) and the rest of the heating
in the house is fine. I balanced the rads a couple of weeks ago to see
if that might help, but it didn't.

The plumber says it's working, and that UFH is just "very subtle." I
agree there is some heat going into the floor, and I realise the floor
won't be as hot as a radiator or anything, but I was expecting at
least *discernible* heat from the floor when walking on it in bare
feet. Is that not the case?

If anyone has any tips, I'd be grateful. I know next to nothing about
plumbing though.

The water from the boiler is cooled before it goes into your manifold
and on to heat the floor. On ours, there is a thermostat near the
manifold (looks a bit like the head of a thermostatic valve) which
sets the temperature of the water for the UFH. Ours is currently set
on the lowest setting (about 35 degrees I think). If you put you hand
on the manifold, it doesn't feel that warm - it is just below body
temp! For our room, Polypipe suggested a temp of 52 degrees. Maybe
yours is set too low?

In terms of heat output, when the pipes were laid, do you know how
close together they were? Obviously the closer they are the more heat
you will get out from them.

Also, how long have you had the heating on for? I have the pipes laid
in a concrete floor and it takes a good day (or longer) for it to heat
up with the UFH on continuously.

It is a bit deceiving as the heat is very subtle it is nothing like a
scorching radiator but if your room doesn't get above 17 degrees,
something doesn't seem right.

The only other thing I can think of is that the manifold flow rates
can be adjusted for each circuit. Might be worth checking with the
manufacturer to see what they should be set on. Polypipe do a free
technical spec for your room and give you these figures, pipe layout,
temp etc.

BlueJohn
wibbled on Saturday 09 January 2010 15:46

We've just had an extension built and we specified wet underfloor
heating for it (by Osma/Wavin). The plumber's installed it, the
manifold gets warm, as do the flow and return pipes, but they're not
nearly as hot as the rads, and I can barely detect any heat emerging
from the floor at all even if I turn the wall thermostat up to 25C.
I've never seen the ambient temp in the room go higher than 17C even
with the boiler temp full blast at about 80C.

On top of the heating boards is 17mm plywood, some thin underlay
(recommended by the manufacturers for UFH) and then B&Q click-to-fit
wooden boards (also said on the pack that they would be OK for UFH).

We've got a beefy combi boiler (15 lit/m) and the rest of the heating
in the house is fine. I balanced the rads a couple of weeks ago to see
if that might help, but it didn't.

The plumber says it's working, and that UFH is just "very subtle." I
agree there is some heat going into the floor, and I realise the floor
won't be as hot as a radiator or anything, but I was expecting at
least *discernible* heat from the floor when walking on it in bare
feet. Is that not the case?

If anyone has any tips, I'd be grateful. I know next to nothing about
plumbing though.

In the UFH installations I've seen, the floor was comfortably warm.

There is a significant thermal lag though. How long have you had it running?

The other thing - has the mixer valve been adjusted to the correct setting?

--
Tim Watts

You know you need more insulation when the snow blanket on the roof makes
the house 3 degrees warmer...

On Sat, 9 Jan 2010 07:46:34 -0800 (PST), BlueJohn wrote:

The plumber says it's working, and that UFH is just "very subtle." I
agree there is some heat going into the floor, and I realise the floor
won't be as hot as a radiator or anything, but I was expecting at
least *discernible* heat from the floor when walking on it in bare
feet. Is that not the case?

Just but there is a very long thermal lag in UFH. Lag measured in
days rather than hours and you have lots of "insulation" over the
floor.

Sister has under floor heating covered by stone flags, they aren't
cold and you don't get cold feet if you stand still for any length of
time in bare feet but "warm" they are not.

The feed to the under floor pipe work will be thermostatically
controlled somewhere to around 40C if that, so winding the boiler
output up to 80C won't have any real affect on the UFH.

--
Cheers
Dave.

sets the temperature of the water for the UFH. Ours is currently set
on the lowest setting (about 35 degrees I think). *If you put you hand
on the manifold, it doesn't feel that warm - it is just below body
temp! *For our room, Polypipe suggested a temp of 52 degrees. *Maybe
yours is set too low?


Ours is set to maximum. I've no idea what temp it's running at, but he
manifold feels almost at medium-ish radiator heat.

In terms of heat output, when the pipes were laid, do you know how
close together they were? *Obviously the closer they are the more heat
you will get out from them.


They were the standard width from the manufacturers as they were set
in to insulated boards - about 6 inches apart.

Also, how long have you had the heating on for? *I have the pipes laid
in a concrete floor and it takes a good day (or longer) for it to heat
up with the UFH on continuously.


It turns on in the morning at about 7:30, it goes off at about
11:00pm. Never have I seen the thermostat on the wall (the one that
controls the UFH) rise above 17C, and it's set to it's maximum of 25C.

It is a bit deceiving as the heat is very subtle it is nothing like a
scorching radiator but if your room doesn't get above 17 degrees,
something doesn't seem right.


If "subtle" means "running it for 12 hours at apparently maximum
output and we feel next to no warmth" then yes, it's subtle alrighty.
About the most subtle use of £1,800 I've ever spent in fact.

BTW this is wet (not electric) UFH and it's in bats suspended between
wooden joists (not in concrete/stone).

The only other thing I can think of is that the manifold flow rates
can be adjusted for each circuit. *Might be worth checking with the
manufacturer to see what they should be set on. *Polypipe do a free
technical spec for your room and give you these figures, pipe layout,
temp etc.

I think I'm going to have to give them a call.

Thanks for your help though.

On 9 Jan, 17:57, BlueJohn wrote:
Ours is set to maximum. I've no idea what temp it's running at, but he
manifold feels almost at medium-ish radiator heat.

Are there no markings on whatever control sets it? Ours is clearly
marked, from 35C to 60C, and we run it in the 40-45C range.

If "subtle" means "running it for 12 hours at apparently maximum
output and we feel next to no warmth" then yes, it's subtle alrighty.

I've not measured the maximum rate-of-change of room temperature that
our system can achieve but I'd guess it's in the region of 0.5C per
hour even in the current weather conditions. Ours is a modern, well-
insulated house.

BTW this is wet (not electric) UFH and it's in bats suspended between
wooden joists (not in concrete/stone).

So you have little or no thermal storage in the floor itself? That's
very different from our system (wet UFH in concrete screed) so I'm not
sure how it ought to behave.

Richard.
http://www.rtrussell.co.uk/

BlueJohn
wibbled on Saturday 09 January 2010 17:57

sets the temperature of the water for the UFH. Ours is currently set
on the lowest setting (about 35 degrees I think). If you put you hand
on the manifold, it doesn't feel that warm - it is just below body
temp! For our room, Polypipe suggested a temp of 52 degrees. Maybe
yours is set too low?


Ours is set to maximum. I've no idea what temp it's running at, but he
manifold feels almost at medium-ish radiator heat.

Normally you wouldn't want it too hot in a solid floor as you risk cracking
the screed - but as yours is in a suspended floor, there's less risk.

In terms of heat output, when the pipes were laid, do you know how
close together they were? Obviously the closer they are the more heat
you will get out from them.


They were the standard width from the manufacturers as they were set
in to insulated boards - about 6 inches apart.

Are they set into heat spreader plates?


Also, how long have you had the heating on for? I have the pipes laid
in a concrete floor and it takes a good day (or longer) for it to heat
up with the UFH on continuously.


It turns on in the morning at about 7:30, it goes off at about
11:00pm. Never have I seen the thermostat on the wall (the one that
controls the UFH) rise above 17C, and it's set to it's maximum of 25C.

It is a bit deceiving as the heat is very subtle it is nothing like a
scorching radiator but if your room doesn't get above 17 degrees,
something doesn't seem right.


If "subtle" means "running it for 12 hours at apparently maximum
output and we feel next to no warmth" then yes, it's subtle alrighty.
About the most subtle use of £1,800 I've ever spent in fact.

BTW this is wet (not electric) UFH and it's in bats suspended between
wooden joists (not in concrete/stone).

The solid floor UFH is normally ready reckoned to give about 100W/m2 but I
have no idea what a suspended floor system is like.

What have you got between the pipes and your feet? Wooden boards and carpet
for example?

--
Tim Watts

You know you need more insulation when the snow blanket on the roof makes
the house 3 degrees warmer...

On 9 Jan, 15:46, BlueJohn wrote:
We've just had an extension built and we specified wet underfloor
heating for it (by Osma/Wavin). The plumber's installed it, the
manifold gets warm, as do the flow and return pipes, but they're not
nearly as hot as the rads, and I can barely detect any heat emerging
from the floor at all even if I turn the wall thermostat up to 25C.
I've never seen the ambient temp in the room go higher than 17C even
with the boiler temp full blast at about 80C.

On top of the heating boards is 17mm plywood, some thin underlay
(recommended by the manufacturers for UFH) and then B&Q click-to-fit
wooden boards (also said on the pack that they would be OK for UFH).

We've got a beefy combi boiler (15 lit/m) and the rest of the heating
in the house is fine. I balanced the rads a couple of weeks ago to see
if that might help, but it didn't.

The plumber says it's working, and that UFH is just "very subtle." I
agree there is some heat going into the floor, and I realise the floor
won't be as hot as a radiator or anything, but I was expecting at
least *discernible* heat from the floor when walking on it in bare
feet. Is that not the case?

If anyone has any tips, I'd be grateful. I know next to nothing about
plumbing though.

Probably a daft question but does your UFH manifold have a pump on it?
How many circuits do you have?

"BlueJohn" wrote in message
...
We've just had an extension built and we specified wet underfloor
heating for it (by Osma/Wavin). The plumber's installed it, the
manifold gets warm, as do the flow and return pipes, but they're not
nearly as hot as the rads, and I can barely detect any heat emerging
from the floor at all even if I turn the wall thermostat up to 25C.
I've never seen the ambient temp in the room go higher than 17C even
with the boiler temp full blast at about 80C.

On top of the heating boards is 17mm plywood, some thin underlay
(recommended by the manufacturers for UFH) and then B&Q click-to-fit
wooden boards (also said on the pack that they would be OK for UFH).

We've got a beefy combi boiler (15 lit/m) and the rest of the heating
in the house is fine. I balanced the rads a couple of weeks ago to see
if that might help, but it didn't.

The plumber says it's working, and that UFH is just "very subtle." I
agree there is some heat going into the floor, and I realise the floor
won't be as hot as a radiator or anything, but I was expecting at
least *discernible* heat from the floor when walking on it in bare
feet. Is that not the case?

If anyone has any tips, I'd be grateful. I know next to nothing about
plumbing though.

Hello,

I recently installed wet UFH in a 10m2 conservatory, using a kit bought
online. I had way too much pipe so laid it at 100mm centres, with 2
circuits, on top of 4" foil-backed foam insulation, and then laid 75mm
screed over the top, with porcelain tiles over that.
It's on it's own zone with it's own programmable stat, fed from a 10 year
old back boiler which wasn't sized with this in mind!
The mixer valve is set to max, and the floor takes a few hours to get warm
after switch-on, but once it is stays around 35ºC all day (according to my
IR thermometer), maintaining the conservatory at 20ºC. The boiler seems to
be coping fine, once the conservatory is up to temperature it gets a few
short top-ups every hour.
It's become the dog's favourite room to lay in...!

In your system it may be that the underlay and the wood floor are acting as
insulation to the hot pipes.

Alan.

On Sat, 09 Jan 2010 07:46:34 -0800, BlueJohn wrote:

We've just had an extension built and we specified wet underfloor
heating for it (by Osma/Wavin). The plumber's installed it, the
manifold gets warm, as do the flow and return pipes, but they're not
nearly as hot as the rads

they shouldn't - indeed must not - be: should be about 43C flow temp,
obviously lower on the return.

, and I can barely detect any heat emerging
from the floor at all even if I turn the wall thermostat up to 25C. I've
never seen the ambient temp in the room go higher than 17C even with the
boiler temp full blast at about 80C.

On top of the heating boards is 17mm plywood, some thin underlay
(recommended by the manufacturers for UFH) and then B&Q click-to-fit
wooden boards (also said on the pack that they would be OK for UFH).

We've got a beefy combi boiler (15 lit/m)

that's the hot water output to taps which is quite irrelevant to heating
radiators or UFH

and the rest of the heating in
the house is fine. I balanced the rads a couple of weeks ago to see if
that might help, but it didn't.

The plumber says it's working, and that UFH is just "very subtle." I
agree there is some heat going into the floor, and I realise the floor
won't be as hot as a radiator or anything, but I was expecting at least
*discernible* heat from the floor when walking on it in bare feet. Is
that not the case?

Yes, it should be comfortably warm, and so should the room if the system
has been properly designed and installed.



If anyone has any tips, I'd be grateful. I know next to nothing about
plumbing though.

The keys are how hot the water going into the UFH is, how hot the water
coming out of it is, how fast the water is flowing through the UFH, and
how much heat is being lost downwards from the floor. You can measure the
first two (flow and return temps). The flow rate may be indicated by a
little gauge on the manifold but otherwise is hard to measure. How much
heat is being lost downwards depends on the construction of the floor.

Did you see (and better still, photograph) the floor being constructed?

--
John Stumbles -- http://yaph.co.uk

Life is nature's way of keeping meat fresh

On Sat, 09 Jan 2010 08:20:49 -0800, Lee Nowell wrote:

Also, how long have you had the heating on for? I have the pipes laid
in a concrete floor and it takes a good day (or longer) for it to heat
up with the UFH on continuously.

Something wrong there then. Should be no more than an hour or two even
with a thickish concrete slab.



--
John Stumbles -- http://yaph.co.uk

My karma ran over my dogma

YAPH wrote:
On Sat, 09 Jan 2010 08:20:49 -0800, Lee Nowell wrote:

Also, how long have you had the heating on for? I have the pipes laid
in a concrete floor and it takes a good day (or longer) for it to heat
up with the UFH on continuously.

Something wrong there then. Should be no more than an hour or two even
with a thickish concrete slab.



Oh the floor may be warn in an hour, but the actual rate at which it
transfers to the rooms is pretty low.

We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember BlueJohn
saying something like:

On top of the heating boards is 17mm plywood, some thin underlay
(recommended by the manufacturers for UFH) and then B&Q click-to-fit
wooden boards (also said on the pack that they would be OK for UFH).

Probably too much insulation on top of the pipes, in the form of a
floor, and I suspect there were no heat spreader plates in the system.
If the pipes were fitted straight into a moulded foam carrier, the heat
has to rise just above the pipes and can't spread out very much. This is
also assuming the foam pipe trays were well insulated underneath, as
heat robbing undersides might be contributing to the problem. How thick
are these foam trays, and were they fitted straight on top of concrete,
or in a joist gap and if a joist gap, was the gap filled with rockwool?
How much foam is under the pipe when it is fitted in the tray?

On Sat, 9 Jan 2010 09:57:57 -0800 (PST), BlueJohn
wrote:

BTW this is wet (not electric) UFH and it's in bats suspended between
wooden joists (not in concrete/stone).

We have underfloor in concrete downstairs and aluminium heat spreaders
between joists upstairs. Downstairs you feel the warm floor more than
upstairs. If you put a cushion on the floor for about 30 mins how
warm does it feel underneath it?

You can use the cushion and thermometer to map the heat distribution
quite accurately by the way. Simply place the cushion on the floor
for a fixed time (about 10 - 45 minutes, the shorter the better) and
note the temperature on a thermometer placed between the floor and the
cushion. Repeat in a grid pattern across the whole room.

On Sun, 10 Jan 2010 10:08:20 +0000, The Natural Philosopher wrote:

Oh the floor may be warn in an hour, but the actual rate at which it
transfers to the rooms is pretty low.

Fair enough: depends on relative output of floor and heatloss of room. But
the OP was complaining that the floor didn't even get warm.

--
John Stumbles

Hypnotising Hypnotists Can Be Tricky

John Stumbles wrote:
On Sun, 10 Jan 2010 10:08:20 +0000, The Natural Philosopher wrote:

Oh the floor may be warn in an hour, but the actual rate at which it
transfers to the rooms is pretty low.

Fair enough: depends on relative output of floor and heatloss of room. But
the OP was complaining that the floor didn't even get warm.

it may well not if the heating input is marginal and the room is cold.

My open floor spaces are not hugely above ambient at full chat on the
heating. It gets very warm under the sofa though. Everywhere else the
heat goes straight into the air by and large.

I am runing at 100W/sq meter max. That is NOT a lot of heat output.

Th e pipe runs through the corridors at up to 6 times that, do get
perceptibly warm. Feline resting area, that.

On Sun, 10 Jan 2010 22:20:18 +0000, The Natural Philosopher wrote:

I am runing at 100W/sq meter max. That is NOT a lot of heat output.

It is what it is. The $64K Q is what's the heatloss of the room?

--
John Stumbles -- http://yaph.co.uk

My karma ran over my dogma

"BlueJohn" wrote in message
...
We've just had an extension built and we specified wet underfloor
heating for it (by Osma/Wavin). The plumber's installed it, the
manifold gets warm, as do the flow and return pipes, but they're not
nearly as hot as the rads, and I can barely detect any heat emerging
from the floor at all even if I turn the wall thermostat up to 25C.
I've never seen the ambient temp in the room go higher than 17C even
with the boiler temp full blast at about 80C.

On top of the heating boards is 17mm plywood, some thin underlay
(recommended by the manufacturers for UFH) and then B&Q click-to-fit
wooden boards (also said on the pack that they would be OK for UFH).

We've got a beefy combi boiler (15 lit/m) and the rest of the heating
in the house is fine. I balanced the rads a couple of weeks ago to see
if that might help, but it didn't.

The plumber says it's working, and that UFH is just "very subtle." I
agree there is some heat going into the floor, and I realise the floor
won't be as hot as a radiator or anything, but I was expecting at
least *discernible* heat from the floor when walking on it in bare
feet. Is that not the case?

If anyone has any tips, I'd be grateful. I know next to nothing about
plumbing though.


Well for sure something's wrong as the room isn't up to the design
temperature which will likely be 21C with an outside air temp of -1C, ie. a
22C difference. So either the design is wrong, or the installation is
wrong, or the setup or the usage.

Presumably your system designer did heat loss sums for the extension. You
don't tell us much about it but let's assume it's a fairly normal room built
to today's insulation standards, not stupidly long and thin or uninsulated
etc. UFCH product from the major players claims about 100W/m2 which for
most normal rooms works well. UFCH is getting a bit like lego now, buy the
standard bits, plug them together and it simply works, so it's hard to see
how the designer could have gone very wrong.

Your builder had more latitude to mess up, often they are not experienced in
exotic things like UFCH. The spacing between the pipes is important as too
wide a spacing limits heat output. Screed depth on the solid floor is also
critical as too thick a screed makes the system very slow to respond,
although it should still get there in the end. That said, provided he used
the standard bits and bothered to read the instructions it should simply
work.

Setup is something which is often ignored as it takes time and is a bit
fiddly, something that builders are often not good at. There will be a
thermostat on the manifold which controls the water flow temperature, it
does this by mixing colder return water from the UFCH pipes with hotter
water from the boiler. Obviously this has a major effect on the temperature
of the floors. On my Polypipe system the thermostat is a red knob which
clicks 1 notch per degree, on the OSMA I think (but I'm not sure) it looks
like a horizontally mounted radiator valve, a big white thing with numbers
and a pointer on it. Try turning yours to a hotter setting, the flow pipe
should get hot. It should get to a temperature you don't really want to
hold on to for very long (say 65C-ish).
Each individual heating circuit (one per room usually) will have a way of
restricting its flow in order to balance them. Its quite possible they've
been turned down too much but I don't know how its done on the OSMA. From
memory that system lacks any flow indicators so you may end up having to
measure the temperature of the flow and return of each circuit with a
thermometer (or hand), they should be roughly 11C different. Mind you for
your purposes simply opening them up would at least prove it is capable of
heating the rooms in the short term.
The UFCH is pumped separately form the main heating so I suppose the pump
could be faulty or indeed it could be adjustable and set too low.
There will also be a couple of isolating valves which could restrict the
flow if they weren't open properly.
Wow, I didn't realise there was so much potential to mess up.

Usage of UFCH is a little different than radiator circuits in that it needs
a little while to heat up. People have suggested it needs all day, not on a
properly installed system it shouldn't. Mine gets the screed noticeably
warm in about 30 minutes and fully up to temperature in about 60. The
wooden floors are quicker.

Hope those ramblings help.

"The Natural Philosopher" wrote in message
...
John Stumbles wrote:
On Sun, 10 Jan 2010 10:08:20 +0000, The Natural Philosopher wrote:

Oh the floor may be warn in an hour, but the actual rate at which it
transfers to the rooms is pretty low.

Fair enough: depends on relative output of floor and heatloss of room.
But
the OP was complaining that the floor didn't even get warm.

it may well not if the heating input is marginal and the room is cold.

My open floor spaces are not hugely above ambient at full chat on the
heating.

uh?

On Sun, 10 Jan 2010 23:34:10 +0000, Calvin Sambrook wrote:

Presumably your system designer did heat loss sums for the extension.
You don't tell us much about it but let's assume it's a fairly normal
room built to today's insulation standards, not stupidly long and thin
or uninsulated etc. UFCH product from the major players claims about
100W/m2 which for most normal rooms works well. UFCH is getting a bit
like lego now, buy the standard bits, plug them together and it simply
works, so it's hard to see how the designer could have gone very wrong.

Your builder had more latitude to mess up, often they are not
experienced in exotic things like UFCH. The spacing between the pipes
is important as too wide a spacing limits heat output.


What's perhaps not so readily appreciated is that the length of the loops
of pipe making up the UFH circuits is important too. For example in a
recent installation one area was about 16m^2, and I needed 83 Watts/m^2
to heat it. With a 5C drop between flow and return and I'd have had needed
almost 1 bar to pump the required amount of water around a single pipe
loop - far higher than a typical central heating circulator ("pump") can
manage. However by splitting it into two loops it only requires about 0.16
bar.



--
John Stumbles -- http://yaph.co.uk

Fundamentalist agnostic

YAPH wrote:
On Sun, 10 Jan 2010 22:20:18 +0000, The Natural Philosopher wrote:

I am runing at 100W/sq meter max. That is NOT a lot of heat output.

It is what it is. The $64K Q is what's the heatloss of the room?

low enough to get about 15 degrees rise easily, but I struggle at 20
degrees rise.