installing wet underfloor heating to an extension

[DanDIY]

Hi,
I am just in the process of having a new kitchen 3m x 9m on the back of my house.

I brought an underfloor heating system a couple of months back when the floor was being laid

http://www.underfloorheating1.co.uk/product/standard-2-port-kit

I did a bit of research and found that for the size of the room 2 circuits would be better, due to the length of the pipe runs, the pipes are laid on 100mm insulation board with a suitable screed on top.

I am now getting to finishing the electric and plastering etc and Ive realised that the kit didnt come with any means of control.....I was in a bit of a hurry when I brought it as the screed was booked and I had not sorted the UFH!

The kit has a pump and a manifold, but I need to understand how to drive the pump.

The rest of the system is radiators driven by a combi boiler. The boiler just uses the standard integral timer/programmer that comes with it and a wireless thermostat.

There is a wiring diagram with the kit, but this is not at all clear.

Can I keep my existing room stat? Do I need a second room stat for the kitchen to switch the pump on and off? Do I also take a feed from the boiler/timer so that the pump only cuts in if the CH is working on the boiler? Is there an off the shelf control unit that can do this?

 

[Agile]

Oh dear!

You really must read previous postings to properly understand what is needed.

UFH has a very long heat up time constant so needs to be started about TWO hours before you need the room to be hot.

That requires a full separately timed control.

Mixing rads and UFH is possible but significantly more complicated.

Room stats are rather difficult because as soon as it turns off the UFH carries on heating for another hour. Timed/predictive controls are better. Could even be an opportunity for a Nest!

Tony

 

[DanDIY]

Hi Tony,
Thanks for your input. I realise that my system will not be optimised in its current configuration.

Due to the location of the boiler and pipework it would not be easy to zone off the UFH onto its own time zone at present. I realise that this means that I will now either have the radiators coming on earlier/longer than I need them, or if I keep the boiler times to suit the radiators the slab will probably not get sufficiently warm for the UFH to work.

As the room that the UFH will be in will be the main living space for the house, I was planning on optimising the CH times to suit the UFH and then pairing back the rads in the rest of the house by the use of thermoctatic valves. I was planning on seeing how I got on with it set up like this, if I cant live with it then I will look at running a standalone second zone to the UFH, but this will be a lot of disruption and mess!

 

[Agile]

Have you had a competent heating engineer in to advise on how you can properly zone the property?

Why do you think it cannot be done?

Starting heating two hours early if timed for two periods a day will make the costs about 40% higher!

Tony

 

[DanDIY]

Yes I have had two competent gas safe engineers - both relatives. They are quite able to make the plumbing connections, but electrical control of UFH is not their strong point as this is the first UFH they have looked at.

As I dont have to pay them then I'd rather we try and work through this ourselves with a bit of headscratching.

I didn't say the house couldnt be zoned, we could zone the house, but the boiler is no where near the UFH so it would mean a lot of work to make the pipe runs from the zone switch. I am already living in something that would make Nick Knowles run away crying, so I dont really want to start ripping up any more rooms. If I can get the system serviceable, albrit not as efficient as possible I will be happy. Then once I am moved in downstaris it might be more realistic to look at zoning the ch.

If the heating bills really do go up by 40% then of course I will install a second zone...or some rads! I am not quite sure how you can make this claim though as you dont know how many hours a day I have the heating on for already.... If I have the heating on for only 2 hrs a day then I can see that an extra 2 hrs will be a significant increase, If I have it on for 16 Hrs a day then I dont see that having it on for 18 Hrs would give a very large % increase!

I have run a 5 core flex between the boiler and UFH pump to carry any control signals. There is also a switched spur available for the pump - although the more I think about it, I think that the power for the pump should come via the boiler circuit through the 5 core flex rather than the seperate spur, as I dont want power from 2 circuits in the same system, as it poses an unescessary risk in terms of future maintainance.