Can you run underfloor heating from a existing Radiator pipes?

FrankFalcon

Hi all

This is a bit of a loaded question because I already (part) know the answer. Basically, we are removing our home bit by bit. Two years ago when we were having a new kitchen we literally dug up the kitchen floor and a company laid down a kit and poured screed over it. This kit was then connected to a manifold in the kitchen and then fed from the boiler at that end of the kitchen. To feed that manifold we had to rip the kitchen ceiling down etc which was ok at the time. Later the kitchen was finished and the underfloor heating in the kitchen is brilliant. Now we come to the final piece of the jigsaw. The rear single storey extension. It’s at the other side of the kitchen so there’s no way we can damage our huge kitchen ceiling (to take a feed). So, the only way we can see forward for heating the floor of our new single story extension is either installing electrical underfloor heating (which we’ve been advised is expensive and nowhere near as good as hot water kit) or have a kit that connects to the radiator system on the central heating? Is there such a kit? Can this be done? If it can, any links to any products please? 

Thanks in advance. 

sheenas

Electric systems tend to just keep the floor warm in my experience, but I guess carefully chosen system would work better. Running an additional manifold fed of the existing system could be possible, but would need investigation by a heating supplier.

FreeBear

If you have 15mm copper pipe going to your UFH manifold, it may be possible to tap into the pipe before the manifold for an additional radiator. But much of it would depend on how much heat is "consumed" by the UFH and how big the new radiator is likely to be.

Assuming you are using a gas boiler with a flow temperature of 60-70°C, you can run about 8kW of radiator/UFH  on 15mm copper. 22mm would allow for up to 18kW..

Albermarle

I thought that wet UFH should run at a lower temperature than a wet radiator system ?
So if the two are linked, then either the UFH would run too hot or the radiator would be too cool ?

Mutton_Geoff

FrankFalcon said:

Hi all

This is a bit of a loaded question because I already (part) know the answer. Basically, we are removing our home bit by bit. Two years ago when we were having a new kitchen we literally dug up the kitchen floor and a company laid down a kit and poured screed over it. This kit was then connected to a manifold in the kitchen and then fed from the boiler at that end of the kitchen. To feed that manifold we had to rip the kitchen ceiling down etc which was ok at the time. Later the kitchen was finished and the underfloor heating in the kitchen is brilliant. Now we come to the final piece of the jigsaw. The rear single storey extension. It’s at the other side of the kitchen so there’s no way we can damage our huge kitchen ceiling (to take a feed). So, the only way we can see forward for heating the floor of our new single story extension is either installing electrical underfloor heating (which we’ve been advised is expensive and nowhere near as good as hot water kit) or have a kit that connects to the radiator system on the central heating? Is there such a kit? Can this be done? If it can, any links to any products please? 

Thanks in advance. 

The kit that connects to the radiator circuit is simply another manifold.

The stat in the manifold recirculates colder water to keep the UFH pipes at a lower temp than the CH supply to the rads. You'll need a controller, stat and electrics to the location where you'll put the manifold.

WIAWSNB

Hi FrankF.

As you've been told, forget electric UFH - silly running costs, although it is easy to install.

That's leaves wet UFH, or have you considered skirting radiators? Column rads?

Your new extension will have the highest level of insulation, so should be easy to heat. We had a 6x6m extension built a few years back, and it's heated adequately by only two column rads, each around 400mm wide.

Assuming, tho', that you do want UFH - and I don't blame you (only cost made us decide against it) - then, yes, you can do this, by tapping off your existing CH system, assuming the tapping-off point has an adequate supply; ie, if it's already on the end of a line, already supplying other rads, then you'd need to check it has the capacity. Almost certainly it will have.

However, unless there is a get-around, the UFH will require its own circulating pump and flow thermostat - is there room to place these? This won't be bulky for a single UFH loop, and you should be able to accommodate it inside a small floor cupboard for example, but it needs to be factored in.

And, of course, it'll have its own room thermostat as well.

In essence, the UFH pump will circulate the UFH loop's supply around, and the flow thermostat will then trickle in your CH's hot water to maintain the correct loop temp. Your CH water will likely be at ~60oC or more, whereas the loop will require to be kept much lower than this - around 35o+?

Yes, it will almost certainly be ok.