U/F heating directly off a combi

[chris watkins]

Has anyone taken an under floor heating system straight off a combi or heat only gas boiler without using a blending valve or mixing header ?
If so, did it work & was there any problems with the boiler controlling the water temperature?

The boiler operating temp range can be fixed (heating side only) to 50 - 30deg C on the board.
I know the limitations on the boiler pump but it is a very small circuit & there in maybe another problem as the heating load at -3degC is only around 3.5kW, the boiler has an anti-cycling timer which hold it off for 3mins but just not sure if this will work correctly.
Help Please, thanks Chris.

 

[ShaunCorbs]

Is that the only circuit eg no rads ?

 

[chris watkins]

Yep, it is just a 1 or 2 coil U/F system in a Summer/games room. Bit overkill IMHO but thats what he wants.

 

[ShaunCorbs]

its going to cycle like a mother i would close tee it

if you can set it up right eg the temps cant see why not just label the temp knob as do not touch due to under floor etc

 

[chris watkins]

I have been told you can fix the Temp with a jumper on the board. So at least that won't be a problem.
Thanks Shaun

 

[Sharp Point]

What’s the size of the area that needs the heating Chris?

 

[Rob Foster]

Some on here might say - as I have been told myself - thats DIY !
I think the concept is good -

 

[chris watkins]

What’s the size of the area that needs the heating Chris?

Approx 8x4m stand alone building.

 

[ShaunCorbs]

diy?

 

[chris watkins]

I remember doing a job in London must be at least 25 years ago which was all underfloor, it had 2 large blending manifolds one on each floor, fed by a heat only Ideal iMax condensing boiler on which you could set the operating temperature to give a maximum of 50deg C flow.
I couldn't understand why the boiler was then set up to give high temp water which then had to be blended down to give no more than 50 at the manifolds, it didn't make sense as boiler could have been in condensing mode all the time.

 

[ShaunCorbs]

I remember doing a job in London must be at least 25 years ago which was all underfloor, it had 2 large blending manifolds one on each floor, fed by a heat only Ideal iMax condensing boiler on which you could set the operating temperature to give a maximum of 50deg C flow.
I couldn't understand why the boiler was then set up to give high temp water which then had to be blended down to give no more than 50 at the manifolds, it didn't make sense as boiler could have been in condensing mode all the time.

Separate hot water boiler ?

 

[chris watkins]

Separate hot water boiler ?

Yes, electric cylinder for some reason, it was a large doctors surgery so not much required.

 

[ShaunCorbs]

Yes, electric cylinder for some reason, it was a large doctors surgery so not much required.

Sometimes it's due to them wanting a back up eg heating goes off they can still work etc

 

[Chalked]

Did some shops with a combi and just underfloor, about 5 years ago.
No blending valve and using the combi pump.
I service them every year and so far, no probs.

 

[chris watkins]

Did some shops with a combi and just underfloor, about 5 years ago.
No blending valve and using the combi pump.
I service them every year and so far, no probs.

Thanks Chalked, what was the boiler & did you limit the temperature range ?

 

[Chalked]

24kw vaillant combi.
Rated it down to min kw. And big marker pen on thermostat setting. Bit crude, but does the job.
I think you can adjust max temp on a ecotec.
Boilers are all in locked cupboards, so no one messes with them.