UFH Control - Single room stat control

nxdmsandkaskdjaqd

The underfloor heating is controlled by 2 x heatmiser uh8-rf control units and 8 room thermostats.  These control 12 Ambiente Actuator Valves on the manifold.  

I am trying to set the system up such that the heating is controlled by 1 room thermostat (family room).

If I set all the room stats high such that all the actuator valves are open (except the family stat which is control). When the family room stops calling for heat, the remining stats will still be calling for heat.

Any thoughts on how I do this?

tacpot12

One option would be to connect the zone that is controlled by the family room stat to an external relay, and have all the actuator valves operated by the relay - the relay needs to be able to handle enough current to operate all the actuators at once. I doubt the UH8-RF unit would be able to supply enough current from one zone to activate all the valves, although the valves only draw very small amouts of current. I'm inclined to think you will overload it if you try, and therefore using an external relay will be the safest approach. Someone might come along who has tried to parallel multiple actuators across one zone and can confirm that their unit coped.   

Any competent electrician would be able to help you select an appropriate relay and enclosure.    

nxdmsandkaskdjaqd

tacpot12 said:

One option would be to connect the zone that is controlled by the family room stat to an external relay, and have all the actuator valves operated by the relay - the relay needs to be able to handle enough current to operate all the actuators at once. I doubt the UH8-RF unit would be able to supply enough current from one zone to activate all the valves, although the valves only draw very small amouts of current. I'm inclined to think you will overload it if you try, and therefore using an external relay will be the safest approach. Someone might come along who has tried to parallel multiple actuators across one zone and can confirm that their unit coped.   

Any competent electrician would be able to help you select an appropriate relay and enclosure.    

I was hoping for a simple solution that I was missing.  I really didn't want to have all room stats running the heating.  However your solution is something that I can see working and worth considering.

matelodave

I've got something similar - each room stat activates the heat pump and opens the actuators to control the flow in the designated circuit.

It appears that all you can do is turn the stats down so only the one you want activates the heatpump and then unscrew the actuators from the flow valves to enable the water to flow through the heating circuits disregarding the stat settings. 

Alternatively disconnect the pump control wire from the manifold controller on the manifold that doesn't have the lounge stat, so that only the circuits controlled by that controller operate the pump.

We now disregard the room stats and let the heatpump do its own thing with weather compensation activated and floor flow rates tweaked to achieve the required room temps.

We found that having all the stats trying to control the pump and actuators either caused flow rate problems if, say only the bathroom called for heat and all the others were off - it either pushed most of the water through the bypass valve causing the pump to short cycle or just shut it down with a flow error requiring to be reset.

TBH the more rooms we shut off, the more the unit short cycles. Whereas leaving it running with the weather compensation adjusted to suit, keeps the house (bungalow) warmer with even heat all over. The flow temp seldom gets above around 32 degrees except if its ever so cold when it can get up to 42 - the heatpump just idles away gently. The floor temp never gets much above around 27 degrees but feels warm in the bathroom and kitchen where we have tiles.

IMO underfloor heating and a heatpump are so slow in responding that a room stat is miles behind the curve when an external stat is trying to control it

We also use less electricity because the thing isn't firing up to full bore every time an external stat calls for heat rather than letting the inverter modulate the pump and fan speeds to control the flow temp. We do drop the w/c temp by 3 degrees between 21:00 and 06:00 so the house cools a bit overnight and it does take around three hours for the temp to recover but as we are at home all day and most active in the mornings we don't really notice.

I reckon we've got our heating consumption down to a bit les than 4000kwh a year for our 140m2 bungalow. Total annual consumption for every thing (including using a tumble dryer 3-4 times a week, even in the summer) averages out at 7200kwh a year. With the worst years up to 8600 and the best down to 6000kwh (but that was when we were away for some six weeks in December/January and we turned the heating right down (it did take two days to reheat the place though when we got back)

nxdmsandkaskdjaqd

The Ambiente actuator valves has a commission clip, which holds the value permanently open (the red bit)

https://ambienteufh.co.uk/ufh-product/actuator-valves/

If all the circuits, except the family room, are held open with the clip fitted, would that work?

Keep_pedalling

Having recently moved into a house with UFH, I am just curious why you would even want to do this?

nxdmsandkaskdjaqd

Keep_pedalling said:

Having recently moved into a house with UFH, I am just curious why you would even want to do this?

I am new to ASHP and UFH, but I understand that you need to keep the system running slow at a low temperature.  Rather than the ASHP switching on and off all the time.

Therefore, because I have several room stats there could be a situation, for example, when the HP is just producing hot water for one room.  This you do not want.

Reed_Richards

I know little about underfloor heating but if you have radiators with TRVs there could also potentially be a situation where the HP is producing water for just one room.  But you try to avoid this by balancing the radiators so that they heat each room at the same rate and so every room reaches temperature at the same time.  In fact you would do exactly this even if you were not using TRVs.  So is there no way you can balance the valves on the manifold?  If you just disable the thermostatic control and you don't have balance then you might end up with some rooms permanently too hot and others always too cold.  

matelodave

Reed_Richards said:

I know little about underfloor heating but if you have radiators with TRVs there could also potentially be a situation where the HP is producing water for just one room.  But you try to avoid this by balancing the radiators so that they heat each room at the same rate and so every room reaches temperature at the same time.  In fact you would do exactly this even if you were not using TRVs.  So is there no way you can balance the valves on the manifold?  If you just disable the thermostatic control and you don't have balance then you might end up with some rooms permanently too hot and others always too cold.  

Underfloor manifolds have a flow rate adjuster for each circuit  which allows some control of the water flow (similar to a lock shield valve on a radiator) and thus can vary the temperature output for each zone. The actuator is driven from an external thermostat and just gives on/off control to each zone rather than the apparent progressive modulation of a manual TRV.

I guess that the super duper Hive TRVs (and their ilk) are motor driven and thus more akin to an underfloor actuator insofar as they are on/off rather than progressive like a manual TRV - perhaps someone with more knowledge could help.

If you get the weather compensation adjusted correctly and the flow through the zones properly set then the rooms dont either over or underheat but you can use the timer in a programmable room stat to exercise time control over the zones in rooms that are less used, like the bedrooms or spare rooms.

Although, as I've said before, the combination of underfloor heating and a heatpump can make the system very slow in responding as the floor usually has the thermal inertia of a storage heater. The DeltaT (temp difference between the room temp and floor temp) is usually only around 7-10 degrees and although you do have a much larger heating area than with radiators, it does make it significantly less responsive than a radiator system.

matelodave

heres our story

When we got our Daikin 11kw system with Polypipe overlay underfloor (more responsive than those that are embedded in the slab) it was set up with eight zones, all with programmable stats and a fixed temp of 40 degrees so I started tweaking.

I got hold of a wireless multichannel temperature datalogger so I could monitor what was going on. We had the stats coming on and off at different times and temps according to the room use (bedrooms up a bit in the mornings, down all day and then up a bit at bed time with a set back overnight) Similar in the bathroom, on all a day in the lounge and study, down in the study overnight and up a bit in the lounge in the evening and set back overnight.

The temps were all over the place because the heating couldn't keep up with all the changes. The floor controller relays clacked away as the stats turned them on an off, the bypass valve hissed away for quite a while to maintain the flow rate, especially when several of the rooms were shut down and the heatpump was on and off like a mad thing. and TBH we weren't really all that comfortable except in the lounge after about lunchtime when it had managed to reheat. My wife whinged about the temp in the study which never seemed to get ever so warm after being shut down all night. We also chewed through about 8500kwh of leccy that year (2010 which was quite cold) - thats total consumption - I reckon our non-heating consumption is about 3500kwh, to 5000kwh for heating

After all that I decided to reduce the amount of control by the thermostats and just had them set back by three degrees during the night and lowered them by a couple of degrees in the bedroom/bathroom which not only made it more comfy but our leccy consumption went down by about 800kwh. 

I then decided to set up weather compensation which took a bit of tweaking and now its around 30 degrees when its 15 outside and 42 when its -5 which seems to be about right and we set it back by 3 degrees overnight. If it gets everso cold, which it does sometimes when the wind is blowing and its chucking with rain, I can temporarily increase  the w/c up by a few degrees until the controller bring it back to normal the next day (its 12 degrees outside and our flow temp is 30.9)

All the room valves are open and now nowhere goes below 17 degrees. The lounge gets up to around 20 by the evening but because the floor is generally warm all over and any draughts are warmed by it the whole house is cozy.

 We've now got a place that feels comfortable all the time in all the rooms, The heatpump just idles away 

I dont get the whinging about being cold (even in the study) and our annual leccy consumption is down to around 7200kwh which equates to roughly 3700kwh for heating. I could probably do a bit better but we are comfy, I dont get the whinging and the heatpump, valves and bypass dont fight each other for control.