underfloor pipes underfloor heating

[robbie77]

Hi,

Following on from a previous post about underground pipes for radiators I suspect that I have copper pipes that have little or no protection going underneath to feed radiators in the kitchen.

I should really check but this will involve digging up the concrete floor.

If I do this I was thinking I might as weel fit wet underfloor heating. This is a naive question but can I simply add plastic pipe matrix that flow under the floor and concrete and tile over them all using using my worcester condensing boiler (1yr old) or do I need extra manifolds and gubbins?

I was thinking while my house looks like a building site I should think of alternatives and I have yet to lay floor tiles etc in kitchen

Any advice really appreciated please

 

[mointainwalker]

I'm not up on condensing-boilers, however i read, that from a temperature point-of-view ( output around 50 C ? )they are well suited to UFH.

Obviously I don't know how many available outlets you have on your boiler, but if you just wanted to do one circuit , it might be possible.

The max recommended length of a circuit is 100 m of pipe , so unless you have a very large kitchen (subtract the area under units as these are not heated ) it is probably feasible.

If you are happy with the current heating of the kitchen, you could work out the output of the rads and then use this to calculate (or ask here ) what spacing to use for the pipe.

I don't know UK regs and don't know if they apply to this situation anyway,but you should look to put a minimum of 60 - 100 mm insulation ( depth depends on material used ) under the screed which is also approx 60 mm thick ( for sand/cement)

Tiled finish gives best peformance as regards heating but really anything except thick, solid wood, carpet or vinyl ( ? )

 

[robbie77]

Ah great so it could be possible. Thanks

All I was thinking is using the exisiting rad points to run a heating run in the kitchen that is about 25m2.

Anybody got any ideas on kits I could buy and is it feasible to do myself?

Cheers

 

[robbie77]

An extra output from the boiler was mentioned, is this so I can independantly control the underfloor part with a thermostat control?

 

[mointainwalker]

Your kitchen is really too big for one UFH circuit.

You can get about 100 W/m2 max from a system but that would be with closed spaced pipe - something like 100 mm centres or alternatively 50 W/m2 with 200 mm centres which would be more appropriate for your kitchen.

Would you be happy with 1 kW heating in there ?

I have to add that this is mainly a rhetorical question because 1 kW of UFH is IMO much more efficient than a 1 kW electric fire.

 

[robbie77]

Your kitchen is really too big for one UFH circuit.

You can get about 100 W/m2 max from a system but that would be with closed spaced pipe - something like 100 mm centres or alternatively 50 W/m2 with 200 mm centres which would be more appropriate for your kitchen.

Would you be happy with 1 kW heating in there ?

I have to add that this is mainly a rhetorical question because 1 kW of UFH is IMO much more efficient than a 1 kW electric fire.

That's a good question with this winter we are having in the U.K.
There is a radiator already in the kitchen so maybe I could adopt a "belt n braces" approach? Not wanting a house that jack built but weighing up my options!

 

[robbie77]

Starting to wonder if it's worth the hassle.I could just put a big upright radiator in and save some time and stress.

Anyone reckon it's very good?

Anyone ever fitted something like this

http://www.speedfit.co.uk/part_spec.asp?s=UFHROOMPACK_S1

Cheers

 

[njk]

Hi,

That system works fine, you can have 2 loops on it, which is what you need.
You can also buy a similiar product from continental and uponor, (the ones I have used). I would recommend the continental one, since they offer much better support if you need it.

If you have have concrete floors with the rooms insulated properly, you will get up to 100w per sqm with 200mm pipe centers. If you have any high heat loss areas, (like double french door), you will need to close the spacing to 100-150 on the first few pipes. Thick solid wood and carpets will reduce that, (ufh won't work at all with solid woods over 25mm and carpets with tog over 2.5). Tiles are of course the best choice.

However, as mentioned in a few previous post, if the ufh is fed of a radiator circuit, it will be on at the same times as the radiators, but the ufh will need longer time to function like it should, you can't just boost it for a couple of hours. So if you can, have a separate zone valve and it's own timer.

best of luck.

Lolli

 

[mointainwalker]

@njk

The John Guest site says " a maximum heat output of approx 100W/m2..."

and that is with 100 mm centres.

How do you get your output of 100W at 200 mm centres ?

 

[njk]

I have never used John Guest, only continental and uponor, (wirsbo and unipipe), and I am not impressed if the only get 50w per sqm with 200mm centers.
the output is of course based on the thickness of the screed, flowrate, temprature and floor coverings.
For example to reach 20 C in a room with unipipe 200mm centers, 50C temp and with a floor covering resistance of 0.15 w per sqm (e.g. deep-pile carpet) you will get 90.9 w/sqm.
If you change the floor covering to a heavy parquet blocks (0.10 w/sqm) you will get 94.9 w/sqm and with ceramic tiles you will have to reduce the mixed temprature to 40C and get an output of 99.8 w/sqm, (if you keep the 50C mix you'll get an output of 139.7 w/sqm and 22 C in the room, but the floor would be 34.2 C).

With tiled floors, you can even get over 70w/sqm with joisted floors and space centers at 200mm.


Based on your statement about john guest, it's quite obvious that their system is a lot inferior.

Lolli