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Author Topic: Room stat recomendation  (Read 2646 times)
titan
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« on: December 13, 2012, 06:23:33 PM »

I have started running the heating in our ( not quite finished) self build. It is a wet ufh system with a GSHP. The UFH controls are Möhlenhoff Alpha which came as part of the system. working near the manifold I noticed that  switching the actuator heads on the manifold seemed to by out of sync with the thermostat demand ie closing when there seemed to be demand and the opposite.Unfortunately   Möhlenhoff don't seem to have a UK office so I haven't contacted them but from the technical information on their  site it seem the thermostats have some sort of software that tries to anticipate demand and reduce cycling, which may be great with a gas boiler but not so good with a GSHP ( or even UFH ?) So I am looking for four new thermostats that are accurate ( digital) have a display showing set and desired temperatures,  and simply switch. Any suggestions please.
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paul149
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« Reply #1 on: December 13, 2012, 11:26:00 PM »

I have used these DT200 stats and have found them fine, only show ambient temp normally and when any button (other than OFF)is pressed for 1 sec it will display set temp.
http://www.honeywelluk.com/Documents/User-Guide/pdf/981.pdf

Paul M.
« Last Edit: December 13, 2012, 11:29:31 PM by paul149 » Logged

3.5 kWp (14 x Sanyo H250E01 + SB3000TL) 225' (SW) at 35' Pitch Lat 51.30' (Bristol) Installed cost £2.63/Wp (Nov 2011) now with solarimmersion and 250L unvented dhw (Almost Zero gas input for DHW from Apr to mid Sep)
dhaslam
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« Reply #2 on: December 14, 2012, 12:59:47 AM »

I  have Danfoss TP9000s in all rooms.  They  have both time and temperature settings.   They are battery powered  but with mains voltage switching. 

http://danfoss-randall.co.uk/PCMPDF/736v01.pdf
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BruceB
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« Reply #3 on: December 14, 2012, 07:55:41 AM »

Heatmiser
http://www.heatmiser.co.uk/web/index.php/room-thermostats
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Richard Owen
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« Reply #4 on: December 14, 2012, 09:56:07 AM »

I have used these DT200 stats and have found them fine, only show ambient temp normally and when any button (other than OFF)is pressed for 1 sec it will display set temp.
http://www.honeywelluk.com/Documents/User-Guide/pdf/981.pdf

Paul M.

I'll add another vote for Danfoss controls.

I've used them for two systems, one just UFH and one UFH and radiators mixed. They work well.

I should add that I use them to control the circulators rather than actuators or valves, if that makes any difference.
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titan
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« Reply #5 on: December 19, 2012, 03:47:25 PM »

Thanks for the suggestions, I have spent some time talking with the various manufactures and it seems that most current digital room stats have some sort of proportional temperature software which gives the boiler a fixed timing as the target temperature is being reached, most seem to be either 3 or 6 per hour for varying times. Some allow the time and/or the timings to be changed but not totally inhibited. Obviously this is not mode to run a heat pump with UFH. Besides being able to completely disable this mode  I  also wanted  some other features  with the stat, like no batteries and the ability to digitally display both the actual room temperature and set temperature. One model that seems to meet the bill is the Danfoss TP5000M Si so I now have four of these to install.
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Richard Owen
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« Reply #6 on: December 19, 2012, 06:12:51 PM »

Interesting thought about not using the proportional control.

I use a TP5000M (probably its predecessor) with proportional control turned on (3 hours) with my UFH.

It takes about 3 hours for the floor to warm the room, so if I want the room hot for 7am, I set it for 7am.

Simples. I think? Have I missed anything?
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44 Yingli 230Wp panels feeding into 2x Solar Edge SE5000 inverters.
20x 58mm SE, 20x 58mm SW, Solar Thermal feeding 320l thermal store.
10kW heat pump.
300W of Hydro Power.
titan
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« Reply #7 on: December 19, 2012, 08:29:25 PM »

Are we talking about the same function, I don't think so. On the Danfoss I have I am referring to the Chrono-proportional function other makers call it TPI . This is where even when the thermostat is calling demand  it cycles the boiler on/off  either 3,6,9 or 12 times an hour, not great for a heat pump. What you describe sounds more like Optimum start control, OSC where you can set the time you require the room at temperature by, although the longest time on their chart is 2 hours for a radiator system in a large poorly insulated building, no mention of UFH which is usually only set  a few degree back at night once the building is at temperature.
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Richard Owen
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« Reply #8 on: December 20, 2012, 05:06:15 AM »

Are we talking about the same function, I don't think so.

Indeed we aren't. Cycling a heat pump isn't great.

Sorry.
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44 Yingli 230Wp panels feeding into 2x Solar Edge SE5000 inverters.
20x 58mm SE, 20x 58mm SW, Solar Thermal feeding 320l thermal store.
10kW heat pump.
300W of Hydro Power.
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