'Underfloor heating' off of central heating loop?

[SJRuss]

Hi guys - a thought occured to my plumber the other day as he was putting in the c/heating system,

I'm having a 75mm screed installed in the kitchen to bring the level up. Before the screed goes down, he suggested putting a run of speedfit pipe down and hooking it up to the heating system?

I know the boiler is large enough to contend with the extra run and that it would have to be controllable off the boiler itself, but would it actually be worth doing? There's going to be another 20mm s/cement bed to lay the 25mm calibrated sandstone - I guess that's a fair depth of material to feel the heat through?

Just seems a bit of a bad/pointless idea to me or am I looking into it too hard as usual!?

Thoughts would be appreciated!

Si.

 

[DHTiling]

As far as i have seen , you need a manifold system to control it..

Maybe a question to our sister forum for plumbing might help decide how easy it is.

Plumbing Forum | Plumbing Advice | Plumbers Forums | A forum for plumbers advice in the UK

 

[Richard Edwards]

Worth doing if your at that stage SJ, You'll need Insulation under the Screed, to sit the pipe in, Speedfit and others sell a
performed expanded polystyrene foam former for this. Manifolds are essential with motor control valves with separate room stat.
Best bet would be to get a plumber specialist who is professional trade / trained and used to doing it. They have all the floor
sensor probes to set it all up. Wish I had done it myself in our large and cold conservatory.

 

[Ajax123]

you can do it but the temperature of the water coming from the boiler would be too hot and would damage the screed. However if you were to use a pipe in pipe system such as Rotex or the like you would be able to do it. I see that done in care homes where they want to run rads off the same boiler as the underfloor heating pipes. I thought about doing the same thing in my conservatory but could not easily get the feed pipes from the kitchen through the utility and office without loads of hassle and mess so did not bother.

 

[Ajax123]

Saw a compact system today ion B&Q which had the pipe the valve and the manifold stuff and controls to connect wet UFH direct into the central heating system. £449 inc Vat for 15m2 - seemed a bit pricey but demonstrates it is reasonably easy to do

 

[SJRuss]

Thanks mate:

This one I guess was it?

Plumbeasy Conservatory Underfloor Heating Kit PE/UFHKIT, PE/UFHKIT

Aye - seems relatively straight forward that. I wonder if it's pipe in pipe/twin wall pipe that?

 

[Ajax123]

Thanks mate:

This one I guess was it?

Plumbeasy Conservatory Underfloor Heating Kit PE/UFHKIT, PE/UFHKIT

Aye - seems relatively straight forward that. I wonder if it's pipe in pipe/twin wall pipe that?

it was this one. I can tell you it is deffo not pipe in pipe but as it has its own mixing valve and temerature control not sure it needs to be.

 

[SJRuss]

Nice one fella.

I poked about online a a bit and based on 10.5m2 which is all I need to heat in the kitchen after taking into account base units - I found these babies:

UFH1 Complete Kits :: Underfloor Heating 1

Probably kit 1 or kit 2. Going to call tomorrow for advice - also need to know whether they have to be installed on insulation. As the subfloor already contains the standard b/regs kingspan and 4/5ins of concrete maybe a thinner insulation [25mm] would do? Maybe even thinner - I seem to remember seeing/being recommended an 8mm product when I looked into UFH previously.

Thoughts?

 

[Ajax123]

Under floor heating is slow to response if in concrete screed. It can be used under wood. Although if you are placing a carpet over the top of it you are working against yourself as you have just insulated yourself again the heat from the under floor with a nice wool carpet! Then there is the problem of getting under the floor if you ever need to do any work like electrics forget it your are stuck it all has to come up.

Carpets are ok to go on ugh systems provided they are low tog rated usually maximum 1.5 tog. These are available from a wide variety of suppliers now and carpets should be included in the design phase when setting the underfloor heating design in place. Underfloor heating can be set to run from the central heating in a number of ways.

1. Pipe in pipe systems which are designed to "lag" the pipes such that the surface temperature is within a sensible range to run within the screed

2. By setting up a flow and return manifold which mixes cooler return water with warmer flow water to maintain a constant temperature

3 by installing a return temperature limiting valve ( that's what I did) which pumps warm water into the system and when the temperature drops to an appropriate temperature it releases it back to the boiler for reheating.

Concrete is ok for underfloor heating but will have a significantly slower response time than for example anhydrite screed due to it's latent heat capacity and thermal conductivity. .typically a concrete floor wold take several hours from cold to operational but once it is at that temperature it's efficiency relies almost entirely on heat loss from the room. The less insulation there is the harder the floor has to work to maintain temperature and the more heat needs to pumped into it to keep it warm. The latter bit is no different to any other heat source.

 

[Ajax123]

Getting under the floor is not a massive issue. Just break a bit up and replace it when you have finished the work. There are plenty of pipe joints for ugh these days.