Combi & UFH

[51]

Hi all. Just giving the idea a few turns. I have a worcester 28i combi feeding the rads upstairs only. I have no rads downstairs as of yet and if I did (when I do) the downstairs it will just be hooking in 3 more rads. But started wondering about a wet underfloor heating system heated by the combi. The lounge is about 4.5m x 3.5m. The dining room is about 4m x 3m and dining room. The dining room has a wall opening into the kitchen and the kitchen has a tiled on concrete floor. So I'm only looking at UFH in the 2 rooms and going no where near the kitchen floor (manner of speaking) Plus UFH in the hall.

Is this feasible?

Thanks.

Arthur

[The Natural Philosopher]

Yes. However to do it properly and efficiently you need

- a lot of underfloor insulation. This makes a HUGE impact on efficiency. Don't even think about it unless you are prepared to rip up and relay floors.

- decent room insulation. Peak output of floors, especially if covered in wood, and or carpets, is not high. You can get 50W/sq meter easily,

100W is doable but 200W is almost a dream..check the heatloss in the hose and if too high, insulate the walls and windows FIRST.

- a separate pump and temperature reducing valve for the UFH. It needs to run on colder water than radiators. This is a fixed cost overhead that makes small installations more expensive than they should perhaps ideally be.

- a separate timer and thermostat - due to the time lag, you need a different regime for UFH, and usually a separate thermostat.

- PROBABLY a relay, as the secondary pump may well be off when there is the boiler pump is on. I.e. you don't want every instance of normal CH heat to start the UFH pump. The wiring gets 'interesting;' and generally unless you use extra motorized valves, a relay is used to make an extra contact.

Have a look at

Some educational stuff there.