wet underfloor heating

[hoppo4.2]

so after the unwanted decision to dig out all of my floors and concrete them ive decided that i might as well "do it proper".

i have a new combi boiler and rads waiting to go in but as the floors are coming up id like to fit underfloor heating in the kitchen/dinner as it will stop the planned slate floor from freezing my feet as well as save me the task of finding some wall space to mount the rads.

so the question is can i run wet underfloor heating with a combi system ?
some that i have seen have there own pump is this really needed?
how much insulation should i use under the concrete some have said as much as 12" but i think the house would fall down if i dug it out that far.

also is there anything else i should know about these wet systems ?

thanks guys your help is much appreciated

[Gingerbread Man]

You don't have to run UFH in concrete....

[dirkgently]

hoppo4.2 said:

so the question is can i run wet underfloor heating with a combi system ?

Yes

hoppo4.2 said:

some that i have seen have there own pump is this really needed?

Maybe

hoppo4.2 said:

how much insulation should i use under the concrete some have said as much as 12" but i think the house would fall down if i dug it out that far.

75mm minimum

[VR6toFlat6]

I'm my experience of underfloor heating the floor takes a good hour to warm up and stays warm for at least an hour after the heat goes off. so if you want the heat to evenly distribute between radiator rooms and u/f heated rooms ideally you need some way of setting the u/f to heat an hour before the test of the house.

[Arthur Jackson]

I would run the UFH and main heating as two zones of an 'S' Plan. This enables you to run them at different times. Yes, you need a pump...and a mixing valve.

[caziques]

Arthur Jackson said:

I would run the UFH and main heating as two zones of an 'S' Plan. This enables you to run them at different times. Yes, you need a pump...and a mixing valve.

Mixing valve is a must - maximum temperature of water into concrete is 45c - much lower than conventional rads.

There are other considerations when laying the pipe - one important one being that you should use a spiral pattern to even heat across the floor - invariably in "grand designs" the pipe is layed wrongly leading to a hot and cold end.