A tenant of my boss's is kicking up about the gas fired underfloor
heating, he keeps on fiddling with the program which basically has 6
time settings and I had left it to drop to 15C from 9:00 to 15:00 then
rise to 23 till 21:00 and22:00 then drop back to 18 till 5:00 when it
rises to 21 C again.

He switches it off in the 9:00-15:00 and 22:00-5:00. This means
bungalow is cold when he gets up at 7:30 and overshoots to 26C mid
evening.

Never having been involved with underfloor apart from this building
what is the likely time lag on a 50mm screed over 100mm celotex in a
building drylined with 50mm celotex and 200mm fibreglass in the roof?

AJH

In message ,
writes
A tenant of my boss's is kicking up about the gas fired underfloor
heating, he keeps on fiddling with the program which basically has 6
time settings and I had left it to drop to 15C from 9:00 to 15:00 then
rise to 23 till 21:00 and22:00 then drop back to 18 till 5:00 when it
rises to 21 C again.

He switches it off in the 9:00-15:00 and 22:00-5:00. This means
bungalow is cold when he gets up at 7:30 and overshoots to 26C mid
evening.

Never having been involved with underfloor apart from this building
what is the likely time lag on a 50mm screed over 100mm celotex in a
building drylined with 50mm celotex and 200mm fibreglass in the roof?


I think you have to measure it - somewhere in the order of an hour, IWHT

--
geoff

On Mon, 29 Oct 2012 22:50:17 +0000, geoff wrote:

Never having been involved with underfloor apart from this building
what is the likely time lag on a 50mm screed over 100mm celotex in a
building drylined with 50mm celotex and 200mm fibreglass in the roof?

I think you have to measure it ...

Best way something that can record the temp every 5 mins then export that
data and plot it to see how fast the place can be made to warm up.

- somewhere in the order of an hour,

I think it will be some what slower than that. It might make 0.5C/hour on
the room temp. 50mm of screed has a lot of thermal mass, as indicated by
the massive overshoot.

In my view underfloor heating is good to provide the baseline heat
required in a longish time scale of many hours. Rather than what many now
expect switch on the heating at 15C and be nice and be a cosy 20C in less
than an hour. Because underfloor heating is not very good at such
"instant heat" you do need something else that will heat the room(s)
quickly should there be a need.

--
Cheers
Dave.

In message ,
writes
A tenant of my boss's is kicking up about the gas fired underfloor
heating, he keeps on fiddling with the program which basically has 6
time settings and I had left it to drop to 15C from 9:00 to 15:00 then
rise to 23 till 21:00 and22:00 then drop back to 18 till 5:00 when it
rises to 21 C again.

He switches it off in the 9:00-15:00 and 22:00-5:00. This means
bungalow is cold when he gets up at 7:30 and overshoots to 26C mid
evening.

Never having been involved with underfloor apart from this building
what is the likely time lag on a 50mm screed over 100mm celotex in a
building drylined with 50mm celotex and 200mm fibreglass in the roof?

I take it the tenant is paying the gas bill.

My understanding of wet under floor systems is that they are best left
running with local roomstats to control the temperature. Obviously this
requires a manifolded system with individual control valves.


I would say that the overshoot indicates an over high water temperature.

Could you do some sums based on the building thermal losses and show how
little gas is saved by this interference?
--
Tim Lamb

wrote in message
...
A tenant of my boss's is kicking up about the gas fired underfloor
heating, he keeps on fiddling with the program which basically has 6
time settings and I had left it to drop to 15C from 9:00 to 15:00 then
rise to 23 till 21:00 and22:00 then drop back to 18 till 5:00 when it
rises to 21 C again.

He switches it off in the 9:00-15:00 and 22:00-5:00. This means
bungalow is cold when he gets up at 7:30 and overshoots to 26C mid
evening.

Never having been involved with underfloor apart from this building
what is the likely time lag on a 50mm screed over 100mm celotex in a
building drylined with 50mm celotex and 200mm fibreglass in the roof?

AJH
There are long time lags on under floor heating buried in concrete. (hours)
It is fairly pointless turning the heating off at all on a daily basis.
The best you came expect is a swing of three or four degrees.
A lot depends on how thick the concrete is and how much insulation is below
it.
The only alternative is to use the floor heating as background heat and some
other source as an intermittant top up.

On Oct 30, 8:43*am, Tim Lamb wrote:
My understanding of wet under floor systems is that they are best left
running with local roomstats to control the temperature. Obviously this
requires a manifolded system with individual control valves.

Exactly, that's what we have here - 6 independent zones with their own
roomstats (and clocks that need changing twice a year!). They are
mostly programmed for 17C overnight and 20.5C during the day, but the
system is never 'off'.

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

On Mon, 29 Oct 2012 22:33:15 +0000, wrote:

A tenant of my boss's is kicking up about the gas fired underfloor
heating, he keeps on fiddling with the program which basically has 6
time settings and I had left it to drop to 15C from 9:00 to 15:00 then
rise to 23 till 21:00 and22:00 then drop back to 18 till 5:00 when it
rises to 21 C again.

He switches it off in the 9:00-15:00 and 22:00-5:00. This means
bungalow is cold when he gets up at 7:30 and overshoots to 26C mid
evening.

Never having been involved with underfloor apart from this building
what is the likely time lag on a 50mm screed over 100mm celotex in a
building drylined with 50mm celotex and 200mm fibreglass in the roof?

AJH

I installed UFH in a renovated shower room earlier this year and I put
1-wire sensors in various places. The floor dropped from 27C at 21:30
last night to 21C at 06:00 this morning. Yesterday it rose from 19C to
27C in 4.5 hours. The room temperature dropped by about 1C overnight.
This is with about 80mm screed over 100mm PU insulation.

Sounds as if you need to fit a dummy controller!

wrote:
[snip]

Never having been involved with underfloor apart from this building
what is the likely time lag on a 50mm screed over 100mm celotex in a
building drylined with 50mm celotex and 200mm fibreglass in the roof?

With a similar set up and 37C water supply to the UFH with a Heatmiser
manifold and zone control it takes about 90 minutes to get to "erindoors"
comfortable with an external temperature below 9C. This can be improved on
by programming the zones to warm up bedrooms and bathrooms first then the
living areas.

Like you I find it best to keep all of the areas around 16 when not in use.
You might consider dropping the night time temperature.

Tell the silly bugger to stop ****ing about or to sling his hook.

--
€¢DarWin|
_/ _/

wrote:

A tenant of my boss's is kicking up about the gas fired underfloor
heating, he keeps on fiddling with the program which basically has 6
time settings and I had left it to drop to 15C from 9:00 to 15:00 then
rise to 23 till 21:00 and22:00 then drop back to 18 till 5:00 when it
rises to 21 C again.

He switches it off in the 9:00-15:00 and 22:00-5:00. This means
bungalow is cold when he gets up at 7:30 and overshoots to 26C mid
evening.

Never having been involved with underfloor apart from this building
what is the likely time lag on a 50mm screed over 100mm celotex in a
building drylined with 50mm celotex and 200mm fibreglass in the roof?

AJH

Specific Heat Capacity (SHC) of concrete is about 800J/kgK (joules per
KiloGramme per Kelvin. In the absence of better numbers, I will assume this
for sand/cement screed.

Density of screed is about 2000kg/m3

(Both figures vary depending on mix - the above will do as a back-of-fag-
packet calculation). We'll use the same for the screed.

If the UFH is designed to 100W/m2 (a figure fairly typical for wood surface
UFH but it could be higher), then we have 1000W of power going into the
concrete.

In your figures, you have 100kg mass screed per m2.

So this takes 100 x 800 = 80000 Joules to raise it one Kelvin or one degree
C.

If we assume the screed goes between 15 and 21C, you need to input
80000 x (21-15) = 480,000 Joules = 480,000 Watt-seconds.

With 100W input power, that is 4800 seconds = 1 hour 20 minutes just to get
the screed from 15C to 21C before you even really start heating the room
that much.

So basically, several hours lag doing anything.

My inclination would be to set it to run at 18C 24 hours a day and use air
blowers for a fast ramp up in the morning and to top up the difference.

--
Tim Watts Personal Blog: http://www.dionic.net/tim/

"She got her looks from her father. He's a plastic surgeon."

On 29/10/2012 23:52, Dave Liquorice wrote:
On Mon, 29 Oct 2012 22:50:17 +0000, geoff wrote:

Never having been involved with underfloor apart from this building
what is the likely time lag on a 50mm screed over 100mm celotex in a
building drylined with 50mm celotex and 200mm fibreglass in the roof?

I think you have to measure it ...

Best way something that can record the temp every 5 mins then export that
data and plot it to see how fast the place can be made to warm up.

You probably only need to measure it every half hour to get a decent
value for the time constant. It will be sl-o--w. If there are thick
carpets on top of the floor then it could take even longer.

If you tell from a cold start to aim for ambient temp +10C then the time
to get to +7C will be a rough approximation to the time constant.

- somewhere in the order of an hour,

I think it will be some what slower than that. It might make 0.5C/hour on
the room temp. 50mm of screed has a lot of thermal mass, as indicated by
the massive overshoot.

My guess would be 2-3 hours of thermal inertia in the floor mass.

In my view underfloor heating is good to provide the baseline heat
required in a longish time scale of many hours. Rather than what many now
expect switch on the heating at 15C and be nice and be a cosy 20C in less
than an hour. Because underfloor heating is not very good at such
"instant heat" you do need something else that will heat the room(s)
quickly should there be a need.

Understatement if ever there was one. It is useless at fast heating. You
warm up the air inside the room for that.

--
Regards,
Martin Brown

On 29/10/12 22:33, wrote:
A tenant of my boss's is kicking up about the gas fired underfloor
heating, he keeps on fiddling with the program which basically has 6
time settings and I had left it to drop to 15C from 9:00 to 15:00 then
rise to 23 till 21:00 and22:00 then drop back to 18 till 5:00 when it
rises to 21 C again.

He switches it off in the 9:00-15:00 and 22:00-5:00. This means
bungalow is cold when he gets up at 7:30 and overshoots to 26C mid
evening.

Never having been involved with underfloor apart from this building
what is the likely time lag on a 50mm screed over 100mm celotex in a
building drylined with 50mm celotex and 200mm fibreglass in the roof?

AJH

6-8 hours

Really the only way to run that mass of screed is on 24x7 settings. That
way it doesn't overshoot and will actually use less fuel!



--
Ineptocracy

(in-ep-toc-ra-cy) €“ a system of government where the least capable to
lead are elected by the least capable of producing, and where the
members of society least likely to sustain themselves or succeed, are
rewarded with goods and services paid for by the confiscated wealth of a
diminishing number of producers.

My guess would be 2-3 hours of thermal inertia in the floor mass.


I have wet UFH in my conservatory and it takes 2-3 hours to get up to
temperature, longer on COLD days.
It's on it's own zone with an intelligent thermostat, which helps however.

On Tue, 30 Oct 2012 08:41:08 +0000, Tim Lamb
wrote:


I would say that the overshoot indicates an over high water temperature.

Thanks all of you, Tim I'll check if he has fiddled with the injection
temperature.

When I laid the coils in the floor I always intended to fit a fan
coil in the kickspace of the kitchen for a rapid warm up. The boss's
regular plumber then went his own way.

AJH

On Mon, 29 Oct 2012 22:33:15 +0000, wrote:

A tenant of my boss's is kicking up about the gas fired underfloor
heating, he keeps on fiddling with the program which basically has 6
time settings and I had left it to drop to 15C from 9:00 to 15:00 then
rise to 23 till 21:00 and22:00 then drop back to 18 till 5:00 when it
rises to 21 C again.

He switches it off in the 9:00-15:00 and 22:00-5:00. This means
bungalow is cold when he gets up at 7:30 and overshoots to 26C mid
evening.

Never having been involved with underfloor apart from this building
what is the likely time lag on a 50mm screed over 100mm celotex in a
building drylined with 50mm celotex and 200mm fibreglass in the roof?

Several hours. We have ours aiming for 21deg starting at about 14:00
but going off to 16deg at about 20:00 - that gives plenty of heat in
the evening and the temperature starts to fall about 22:30. It aims
for 19 deg starting at about 05:00 and getting there about 07:00. At
0800 it drops back to 16 deg. With warm floors the room temperature
doesn't need to be high to be comfortable in the morning when people
tend to be moving about. The thermostat is a Honeywell one and
doesn't switch the system off - just controls it to varying
temperatures.

On Wed, 31 Oct 2012 17:27:18 +0000, Peter Parry
wrote:

The thermostat is a Honeywell one and
doesn't switch the system off - just controls it to varying
temperatures.

This too is a Honeywell one which acts similarly.

Boss told the chap not to fiddle with the controls and, thanks to
Tim's suggestion, have backed the mixer control from 50(Max) to 40,

Everything seemed hunky dory by 17:00

AJH