Weather Compensation - Is it worth installing on UFH

[FozzieBear]

I have a 4 bedroom bungalow that I re-built 18 yrs ago and installed Hot Water Under Floor heating in the solid floors.

Because the building was rebuilt in two stages I have two manifolds each serving separate parts of the building. One serves the living areas and the other the bedrooms and main bathroom.
In addition to the UFH I have two towel rails on the boiler bypass and two rads in the utility room and adjacent WC which are for drying clothes.

Originally each system was controlled by a separate wired thermostat. one in the lounge and the other in the bedroom corridor.

About 5 Years ago I extended the building adding a garden room and study and utilised some "belt and braces" pipework originally installed in the floor slab "in case" we needed additional radiators to supplement the UFH. Originally the system consisted of 20mm Wirsbo heating loops but the two new extensions have 15mm Uponor heating loops connected to the 15mm Pe-Pex radiator supplies. At the same time I removed the wired thermostats and installed wireless thermostats in each room with actuators fitted to the manifold valves.

The system keeps the bungalow nice and warm but I have noticed of late the floor temperatures have been overly hot to the point of being uncomfortable. This could be that the thermostatic mixing valves are no longer working properly. The other issue is that the heating "lags" considerably behind changes in weather. For example if the temperature drops suddenly outside it take a while for the heating to compensate and come up to temperature. By the time its warmed up the temperature outside has increased again and the building is too warm.

I need to get the UFH serviced after 17 odd years of service as I notice some of the valves are sticking and the mixers might not be working. I was thinking about investing in Weather Compensation to try and iron out the fluctuations. I have a Valliant Condensing Boiler for which you can get a kit.
Does anyone have experience of fitting these and do they work. I am not expecting major returns on fuel economy but better response of the heating to weather changes.
Fozzie

 

[Tipper]

I had weather compensation at my last house using standard Vaillant kit on a Vaillant combi boiler. The heating system was standard radiators. The WC worked well in trimming the house temperature to the external conditions and was particularly noticeable during the UK's fast swings between frost and warm rain!

I now have a bungalow with UFH which is very much like your latest system, ie 2 manifolds, 12 loops/loop valves, 9 zones (room stats), separate bathroom towel rads, etc. I let the boiler/boiler pump do its own thing via a low loss header and the UFH manifolds manage the flow temperature via a thermostatic blender valve and manifold pump.

I have yet to work out how to add weather compensation though due to the obvious conflict with room stats, etc. I'll watch your thread with interest.

 

[Dan Robinson]

Set up properly, the room stats with WC are only there as limiters should you suffer from solar gain or too many visitors.

 

[Agile]

Mr Bear, you have already mentioned the time lag with your UFH system. That's typically 1-2 hours. That's both to heat up and to cool down.

During the daytime the UFH will be well controlled by weather compensation (WC ). But unfortunately when outside temperature is changing rapidly at dawn, dusk and during a eclipse then the thermal lag of the UFH prevents the WC doing its job properly.

My conclusion is that whilst WC is very advantageous, to be most effective and to prevent it making the situation worse then it would need to be inhibited at dusk and dawn.

The reality is that a simple computer program would deal with it very effectively. However the market is so small that the financial returns would not be sufficient to justify anyone designing and marketing one. Not very difficult project for a computer enthusiast.

The Nest WiFi thermostat provides a degree of WC by using weather information from the internet according to its sales information. In addition it "learns" the start times needed to provide the comfort at a target time and they seem to do that quite well. Users seen less convinced about what they do in practice in relation to WC. And they don't have any facility to compensate for the long cool down time of WC.

Tony

 

[Tipper]

Set up properly, the room stats with WC are only there as limiters should you suffer from solar gain or too many visitors.

Interestingly when we were still completing the UFH installation we ran the whole house on just one thermostat located in the hall for convenience. The house temperatures, room by room, remained remarkably even. Even the two areas that didn't yet have UFH were warm. If only one stat is used then weather compensation would be easy I feel.

I did wonder at one point whether to bother at all with 9 zone thermostats as room to room balance can be achieved by balancing the loop flows which you have to do anyway. I found room temperatures varied depending on sun input and wind direction with only one stat.

9 thermostats does give a 'holiday' problem though as rushing round the house as you leave for the airport changing all the stats is a real bore! A temprorary solution is a standard heating programmer which switches the whole lot off when away but this means no frost or low temperature setting available whilst away. This is hopefully being solved by the addition of a master controller for the wifi stat receivers/controllers but I haven't got to grips with linking the 2 manifold/controllers together yet. Haven't had time and I don't want to cock it up during the heating season. I will address this in the summer when the system is off.

 

[Dan Robinson]

Tony, sorry mate, but speaking from experience (as in I have compensated UFH at home) you are talking horlicks about temperature swings. You are forgetting that the internal building temperature does not fluctuate as rapidly as the outside temperature

I'm not convinced about Nests intelligence with regards internet based weather information. But what you are talking about is basic TPi or Chronotherm (manufacturer depending).


Tipper, Honeywell Evo gives you up to 12 zones and a central control panel. Heatmiser also do a system, but it is not as good.

 

[dhutch]

I am interested in this.

My parents have electric night storage underfloor heating, which is the sole source of heat for the house, installed by them in the later 80's. At the time an analog 'weather watcher' control system was installed but never really performed as intended and they have been manually controlling it using a immersion heater timer ever since.

Expect that weather compensation systems have come on leaps and bounds since then, so it may be time for them to invest is something more automated.


Daniel