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Thread: How important is thermostat location?

  1. #1
    Automated Home Jr Member
    Join Date
    Dec 2005
    Posts
    18

    Default How important is thermostat location?

    I am trying to improve the heating control in a small property, I have Heatmiser but the thermostat is on the landing behind a fire door. This often means the other rooms end up too hot or cold. I plan to fit Danfoss Z wave radiator valves controlled by Vera Lite. The property has one open plan space downstairs plus 2 bedrooms bathroom and landing upstairs. I will fit a tripe sensor downstairs so can get the lounge temperature, Up stairs I plan to use a fibaro universal sensor and 4 dallas one wire thermometers.

    The simple way to install the sensors (I have some with a nice stainless probe) would be to drill a small hole from the loft into each room, they would be hidden from sight by some exposed beams. Am I likely to get much higher temperature readings that I will need to compensate for? The ceilings are high so the stats will be about 8' up. Should I go to the trouble of trying to locate them lower in the room?

    Once this is installed I hope I can apply a bit of logic on vera lite to adjust the radiator set points for a more even temperature.

  2. #2
    Automated Home Jr Member
    Join Date
    Dec 2013
    Posts
    41

    Default

    Overall this sounds like a good solution.

    The nice thing about Z-Wave is that you can take multiple different sources of data (inputs) and apply any logic you wish in the controller (in your case the Vera) and then make the outputs react accordingly (in your case the Danfoss valves).

    To sense the temperature accurately in rooms I try to site the sensors at approximately the same height as a light switch would be, in the "most used" area of the room. But it doesn't particularly matter since you can always apply an offset to individual sensors to take into account sub-optimal positioning. There's plenty of options for temperature sensing with Z-Wave - I use the Fibaro Universal Sensor for monitoring my heating pipework (flow, return, hot and cold) and it works well - very accurate and updates can be set to be as often as you need. You could also look at the Fibaro Door & Window Sensor as it can have a DS18B20 1wire sensor installed in it and since it is battery powered could be sited anywhere.

    With regards to your choice of Danfoss - as long as you go for the new LC-13 version which fixes an incompatibility issue with Vera they work well. There's a few things to be aware of though - they don't report the temperature back to the Z-Wave network and they use what's known as an "intelligent heating algorithm". This means that they learn the characteristics of the room that they are in and react to set-point / temperature changes "when they damn well want to" (to put it bluntly!) so for example the room temperature could be 19c and you change the set-point to 22C, the Danfoss will open the valve to whatever percentage it believes is necessary to increase the room by XC over Y minutes.

    The alternative is the StellaZ, which is butt ugly, doesn't have local control or display, but does react to changes in set-point a lot quicker and also reports the temperature back to the Z-Wave network (but obviously this is right next to the radiator, so may not reflect the actual room temperature).

    The only thing missing from your proposed set-up is something to interlock the boiler, something like the Secure Thermostat and Receiver would work well there (there's a single and dual channel receiver for heating or heating & hot water).


    Hope that helps!
    Martyn Wendon
    Vesternet
    Check out my Blog!

  3. #3
    Automated Home Jr Member
    Join Date
    Dec 2012
    Posts
    23

    Default

    Having gone through this with several rooms, and a heat sensor I can move around the house, I realised it was trial and error.

    I would move it, then offset the temperature, then move it again, and offset again.

    It took me about 2-3 weeks of experimenting to find the optimum position and offset.

    I would strongly suggest not permanently mounting the sensor, but initially just try several locations and monitor it.

    Eventually you will find the best placement, plus offset.

    Fon

  4. #4
    Automated Home Sr Member
    Join Date
    Oct 2014
    Location
    Scotland
    Posts
    50

    Default Vera Z-Wave sensor

    Quote Originally Posted by ianh100 View Post
    I am trying to improve the heating control in a small property, I have Heatmiser but the thermostat is on the landing behind a fire door. This often means the other rooms end up too hot or cold. I plan to fit Danfoss Z wave radiator valves controlled by Vera Lite. The property has one open plan space downstairs plus 2 bedrooms bathroom and landing upstairs. I will fit a tripe sensor downstairs so can get the lounge temperature, Up stairs I plan to use a fibaro universal sensor and 4 dallas one wire thermometers.

    The simple way to install the sensors (I have some with a nice stainless probe) would be to drill a small hole from the loft into each room, they would be hidden from sight by some exposed beams. Am I likely to get much higher temperature readings that I will need to compensate for? The ceilings are high so the stats will be about 8' up. Should I go to the trouble of trying to locate them lower in the room?

    Once this is installed I hope I can apply a bit of logic on vera lite to adjust the radiator set points for a more even temperature.
    My recommendation for you is to use the Danfoss LC13 and get Vera Z-Wave Multi-Sensor (Motion, Light, Temp) - aka wall thermostat. You can then configure Vera wall thermostats to work with you LC13 TRVs. This way your wall sensor will measure your room temperature and then control your LC13 TRVs very accurately or by accuracy of 0.5 Centigrade.

    Your LC13 TRV are a dream come through for anyone who uses them. They have very intelligent Fuzzy Logic built in that in some instances will take over if the need arises but these new TRVs work accurately with Vera Lite.

    As for the best location for your wall thermostat - Keep your thermostat height between 1.4 to 1.5 meters as it is the height nearly all manufacturers calibrate their thermostats for. If you stick to this rule you will find you don't need to compensate for heat adjustments because of height difference. I try not to place a thermostat on a outside wall as they are always slightly colder than a inside walls. Also try not to let the sensor face a south facing window directly and always avoid drafty locations.
    Last edited by Hot; 28th October 2014 at 06:59 AM. Reason: additional information

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