This weekends project - UFH - How did I do?

[Mark Gillespie]

Got the edging and pipe in. Connection next weekend..

Some pics of the 3 circuits. For a newbie, how did I do?

Circuit 1;

2; 3; did lay the 2&3 circuits different to my original plan, as it made =

laying easier. The pump, thermostat and manifold are living under the =

suspended floor in the living room, the cutout where the blue sleeves ar= e =

is now filled with polyurathane expanding foam, will carefully trim it o= ff =

tommorrow.

Plumbling it all up and pressure testing next weekend hopefully.

I have LOADS of 16mm pipe left. I might ebay it.. But how common is =

16mm???

[Mark Gillespie]

Last image did not work for some reason.

[Roger Mills]

it interesting. Presumably you're going to screed over it? How are the black clips anchored to the Celotex?

I notice that the pipe density is a lot lower near the centre of each circuit. Is this ususal, and can you rely on the conductivity of the screed to distribute the heat evenly?

[Mark Gillespie]

Yep, 65mm of screed.

How are the

The have splines of them and push in.

I hope so!!! The pipe is VERY stiff, and it's very tricky to get small = =

radius turns. This is best we could achieve!!!

[Tournifreak]

I agree, it is very difficult. If I was doing my UFH system again, one thing I'd do when comparing suppliers is to check the min bend radius of their pipe.

I'm almost certain you will get a cold spot in the centre. I had a smaller gap in one or two places on my floor, and you can feel it. I guess your feet can feel a pretty small temperature difference. Still, it's not really a problem as far as heating the room goes.

Jon.

[The Natural Philosopher]

You will definitely get hot and cool spots..but its better to have the hotter sections at the room edge.

When I put levelling compound over mine, I could see where the pipe s were..it dried out there..

FYI At around 60W/square meter in 75mm screed. the rate of increase of temp of the slab and room is about 1 degree C per hour. One day I will check that with the actual latent heat of concrete..

When my thermostat screwed up in January, it took several days of no heating to drop the room temp to 13C overnight..

[Onetap]

Good IMHO..

You probably know this, but just in case, you need to pressurize it, ensure it's leak tight and keep it pressurized whilst pouring the screed.

Conservatory? You sometimes can't get the required heat output from UFH for buildings with high heat losses, while keeping the floor temperature below the BS recommended maximum (37 degC ISTR).

[Autolycus]

For which change of state? None of them are common in concrete.

[Bob Mannix]

Yes, you're right, he definitely needs to be more Specific ;o)

[Bob Mannix]

(on a more factual OT note ~3350 J kg^-1 K^-1 for concrete)

[Bob Mannix]

So I would have said NP was out by a factor of up to two or three somewhere (which isn't too bad for a guesstimate)

3350 is not far off the number of seconds in an hour, so we can say (roughly) 1Wh (1W being 1J/s) should give a rise of 1degC in 1kg of concrete. 1 metre square of 75mm concrete weighs about 180kg so you would need 180W/m^2 to raise its temperature by 1degC in an hour. That's a factor of three but screed probably has a lower specific heat capacity and density than concrete so say a factor of two out, then a percentage of the mass is pipe anyway, so not far off!

[The Natural Philosopher]

Sorry. SPECIFIC heat... :-)

[The Natural Philosopher]

So how many watt hours per degree C per cu meter..?

[The Natural Philosopher]

Oh the *floor* warms up faster, but there's another 20 tons of iron and steel and brick in the fireplace at least. Plus I remembered its 4" of screed, not three..

Anyway, the time constants are very large. It works very effectively in spring/autumn,when the daytime sunshine really worms the whole place to the extent of not needing heating in the evening at all. And inhigh summer by keeping the place cool in teh afternoons.

Only winter demands an early switchon to be evening comfortable.

[Bob Mannix]

The figures are all approximate because of many factors as you suggest, plus the figures for concrete will depend on how it's mixed, what aggregate is used etc. The theory agrees with you figure well enough given the approximations - it wasn't a factor of 10 out or anything!

[The Natural Philosopher]

Well I simply sat and watched the digital stat strapped to the fireplace...and was quite taken aback at how long it did take top get up to temp.

Its set to 19 degrees, and generally overshoots one degree to 20C in winter..but by then we are in there, and two people plus TV and a few hundred watts of lighting generally keeps it above 19C until we go to bed..

The main point I wanted to make is that with this sort of arrangement, you want to be on at 10 a.m. if you want it warm by 4pm..the actual energy density of the pipes is only just enough to fully warm mine at

-5c outside..if it stays below zero all day and there is no sun, it has to run 24x7 to keep up..