Underfloor Heating with Gas Combi Boiler

patrickwoodcock

Hey,

Just got a small terraced house and am extending it (120q/m) so thought id go the whole hog and install underfloor heating. Has anyone any experience of using a Combi Boiler (fed from mains) to heat underfloor heating and also the hot water (one shower and 3 hot taps). Im on a budget so getting a underfloor heating kit so Ill have the pipes down and have a plumber/electrician connect and commission.

Ive trawled the internet and so far all I have found out is that its possible, and a good system, but nothing on running costs and peoples ideas or problems. Anyone out there have any comments?

Also, can a combo boiler heat each system at different temps? (IE hot water at 60 and underfloor heating at 40?), or do I need a mixer valve on the manifold for the underfloor heating to cool the water?

Thanks for your time and hope to hear comments

twignme

I know you are looking at a gas boiler but I have an oil combi and underfloor heating in my kitchen and hall. I can't give you all the technical specs but it has been configured so that the UF is at 50 and the domestic hot water is at 60 and it works very well. I put in a huge amount of insulation so the boiler doesn't fire up too frequently - it's set to a room temp of 20 deg.

K.Flyer

The short answer is..
Yes its a good system, and even better if its a High Efficiency condensing boiler.
On the combi boiler you have the options to independently adjust the heat output for either hot water or heating. So you can run the heating side at the much lower temperature and keep the hot water at the preferred temp.
Are you using an existing boiler (make / model?) or getting a new one

Wearb

Depending on your lifestyle, underfloor can be great or poor. If you have been used to rads with their quick response time, then be aware that you need to use the slow responding underfloor in a completely different manner. eg No point in coming in the door, turning the heating on and expecting the place to warm up while making a cuppa.

Biggest faux par for this type of installation is not fitting a auto bypasses before the blending valve otherwise it works very well.

patrickwoodcock

Cheers for the info, really helps, trying to make the best of what I can. At the moment there is no heating system so its all from scratch, so will be a new condenser boiler and pipes will be 150mm apart. Thats cool if the boiler can heat water at 2 different temps, am I right in thinking I don't need a blending valve on the manifold so?

patrickwoodcock

patrickwoodcock wrote: »

Cheers for the info, really helps, trying to make the best of what I can. At the moment there is no heating system so its all from scratch, so will be a new condenser boiler and pipes will be 150mm apart. Thats cool if the boiler can heat water at 2 different temps, am I right in thinking I don't need a blending valve on the manifold so?

If you want to fit a combi I'd fit a blending valve as your only a defective diverter valve away from over cooking the under floor.

But you can buy a boiler and set the heating to minimum(which can end in tears) or the more cleverer boilers can have the heating temp fixed between 25-45c and the pump fixed to low speed add a outdoor sensor then your sucking diesel.

patrickwoodcock

Thanks Gary71. Can I clarify, if I got the 'cleverer' boiler, would I need a pump and blending valve on the manifold? Happy to get whats best as I don't want something that will fail in a years time, but also don't want to be buying stuff I don't need. I know ill need a plumber to install when the time comes but great to get it clear in my head. Also any idea of a good boiler? Thanks again

patrickwoodcock

patrickwoodcock wrote: »

Thanks Gary71. Can I clarify, if I got the 'cleverer' boiler, would I need a pump and blending valve on the manifold? Happy to get whats best as I don't want something that will fail in a years time, but also don't want to be buying stuff I don't need. I know ill need a plumber to install when the time comes but great to get it clear in my head. Also any idea of a good boiler? Thanks again

If you pm Dtp1979 he'll let you know the name of the most intelligent boiler I've forgotten.

But if you fit said most intelligent boiler it can be easily programmed to run specifically for under floor with a temperature range of 20-45c on the heating side so no pump or blending valve is required.

Dtp1979

gary71 wrote: »

If you pm Dtp1979 he'll let you know the name of the most intelligent boiler I've forgotten.

But if you fit said most intelligent boiler it can be easily programmed to run specifically for under floor with a temperature range of 20-45c on the heating side so no pump or blending valve is required.

Indeed. I think I know the boiler you're talking about Gary. And not too long ago I did a job similar myself with a combi and underfloor heating.

gctest50

How about sticking in an accumulator tank ?

it'd free you up from having one specific boiler

be easy to add on solar etc in the future ( if you pick the right tank )

Dtp1979

gctest50 wrote: »

How about sticking in an accumulator tank ?

it'd free you up from having one specific boiler

be easy to add on solar etc in the future ( if you pick the right tank )

They've only got a small terraced house. I doubt there's room for an accumulator tank

patrickwoodcock

Thanks again. Yeah in an ideal world if had the space and money id have a buffer tank and air to water heat pump but this aint a bad alternative I hope

patrickwoodcock

Got some great info from Dtp1979 on Ariston Boilers so thanks. Just wondering if anyone has any info on any other makes that do the same job (IE supply to underfloor heating and hot water at different temps so a blending valve and pump are not required at the manifold), or any other experiences with this system?

Thanks

Yellowflower1

patrickwoodcock wrote: »

Got some great info from Dtp1979 on Ariston Boilers so thanks. Just wondering if anyone has any info on any other makes that do the same job (IE supply to underfloor heating and hot water at different temps so a blending valve and pump are not required at the manifold), or any other experiences with this system?

Thanks

Hi Patrick did you find a suitable boiler? I'm starting plumbing from scratch on a cottage renovation and leaning towards combi oil boiler for underfloor and hot water. Would like to add tank for future solar hot water option, is that possible? Thanks

patrickwoodcock

From what I've learned, if your going to install a tank for future solar hot water id use a normal condensing burner (not combi) and have a tank that will accommodate the future pipe feeds. You can get tanks that can have up to 3 sources of heat (EG burner, stove and solar). One step further depending on your budget, if I had the room id install an air to water heat pump as opposed to an oil burner.