Underfloor heating instead of one radiator

[firapara]

Hi Guys,

Building an extension and want to remove one radiator in the living room and use the pipework for underfloor heating in the extension.

Is this ok to do? Can I just replace one radiator with underfloor heating without any other adjustments? I will install two valves on the pipes, so I can close underfloor heating just like a radiator.

I have a newly installed Combi Boiler.

Thanks,

 

[Madrab]

Nope, doesn't work like that unfortunately. UFH doesn't run at the same temp as the rads, unless you are running the system super cool. You would need, at a min a FHV valve to manage that room's floor and air temps.

 

[stem]

UFH is slower to warm up than a radiator, so generally needs to be on longer before the room is warmed. For this reason many UFH users leave it on 24/7. To achieve this the UFH is usually plumbed as a completely separate zone from the radiators with separate controls so that the UFH can be left running when the radiators aren't.

Also, if you happen to be fitting UFH only in an extension part of a room and not any existing part of the same room, it may not cover a large enough area to heat the whole room satisfactorily.

 

[firapara]

Nope, doesn't work like that unfortunately. UFH doesn't run at the same temp as the rads, unless you are running the system super cool. You would need, at a min a FHV valve to manage that room's floor and air temps.

If I fit something like this, then it becomes ok?

Underfloor Heating TCB Unit Single Room FHV Regulating Valve Chrome Plated for Small Rooms – Underfloor Parts

underfloorparts.co.uk

 

[Madrab]

Yep, that's one of the chaps you could fit, that allows the flow temps to be regulated. You would still need to ensure that the loop wasn't too large putting too much strain on the boiler pump.

 

[stem]

Plus a motorised valve so that you can run the UFH separately from the rads. A second circulation pump is usually also installed too. Pumps have different settings for rads (Proportional Pressure) and for UFH (Constant Pressure)....not sure what you would use with a hybrid.

 

[firapara]

Plus a motorised valve so that you can run the UFH separately from the rads. A second circulation pump is usually also installed too. Pumps have different settings for rads (Proportional Pressure) and for UFH (Constant Pressure)....not sure what you would use with a hybrid.

So just installing FHV is not enough? Can I just close all radiators when I run the UHV?

I normally runn heating at 60 degrees, but can go as low as the boiler can, I think the lowest is 50C

 

[Madrab]

So just installing FHV is not enough? Can I just close all radiators when I run the UHV?

Depends on the size of the loop and how you want to control the rooms UFH.

small setup would look like this using the FHV on flow or return, valve dependent

If you want direct zone control of just the living room UFH and temp, then that would need it's own zone valve and stat. If you'd be happy that the UFH goes off when the normal room stat turns off the rest of the heating, then not necessarily needed. As far as a pump is concerned then If the length of the pipe loop gets over a certain size, then the boiler pump may not be able to cope with the demand of the UFH and satisfy the rest of the system at the same time so an extra pump may be needed.

That would normally all come in a single setup with a a manifold with mixing valve, pump, flow meters and actuators controlled by thermostats.

 

[firapara]

Depends on the size of the loop and how you want to control the rooms UFH.

small setup would look like this using the FHV on flow or return, valve dependent

View attachment 329895

If you want direct zone control of just the living room UFH and temp, then that would need it's own zone valve and stat. If you'd be happy that the UFH goes off when the normal room stat turns off the rest of the heating, then not necessarily needed. As far as a pump is concerned then If the length of the pipe loop gets over a certain size, then the boiler pump may not be able to cope with the demand of the UFH and satisfy the rest of the system at the same time so an extra pump may be needed.

That would normally all come in a single setup with a a manifold with mixing valve, pump, flow meters and actuators controlled by thermostats.

Thank you,

How do I know if the loop gets over certain size? Do boiler specs say it, or can I find it somewhere else?

 

[Madrab]

Not really, down to what the system is just now, what you are adding, overall flow required, pump head etc, too many site specific variables to write a spec for it TBH.