Eliminating errors in temperature control

Those who have visited my blog more than once, will probably know about my continuous struggle to get a better control of the temperatures throughout the house, both up- and downstairs.

To demonstrate the biggest ‘problem’ we have here regarding temperature control, I made a chart showing 2 different temperatures. The blue line shows the temperature measured in the living-room, by the internal sensor of our thermostat. The red line shows the temperature measured in the hallway, with an RF temperature sensor.

Oh, and the trends in the chart below could well be just like yours, cause it’s a very common phenomenon:

Temperature charts

Most of the days were sunny, but the last 3 weren’t. The peaks in the blue line (i.e. the temperature in the living-room) are caused by the solar radiation, warming up the living-room to almost 23 degrees! That’s OK of course, but the result is that the central heating will not burn from approx. 12:00 till 18:00. And the whole house, except the living-room, is getting colder and colder.. So no matter what I do, this is the first thing I have to fix -I need a different reference temperature. I know that for quite some time, but never did something about it. Not every thermostat has the ability of connecting a remote temperature sensor to it, I didn’t want to move the thermostat to another location and we sure don’t want to block the sun radiation that’s warming up the living-room for free. (oh and btw: no, the thermostat is not ‘hit’ by direct sunlight).

So last Thursday I added another item to my ever growing collection of hardware to control the temperature inside: a remote temperature sensor.

Honeywell F42010972-001

A week ago I stumbled upon this sensor of which I didn’t even know it existed and immediately decided to buy it and give it a try.

I pulled 2 m. of ‘thermostat wire’ through the wall to my Honeywell Chronotherm Touch Modulation, connected the sensor, configured the thermostat and left the remote sensor dangling in the hallway, near the coat rack and started watching the OpenTherm information.

The remote sensor now replaced the internal sensor of the thermostat and I immediately saw the temperature dropping from 20.5 °C to 19 °C, which is the temperature in our hallway. At the same time, the modulation level of the boiler went up to 100% 🙂 Of course, I’ll have to adjust the ‘room’ setpoint … lowered that one with 1.5 °C as well and things seemed to stabilize again.

That’s part 1 of the story. Part 2 is preventing the heat produced by the boiler flowing to the living-room when it’s not needed there (cause the sun radiation is already produces enough). Well, that’s not that hard – I can control the floorheating pump with an appliance module and switch the pump off@setpoint+0.1°C and back on when the temperature reaches setpoint-0.1°C. Done…

Let’s see what this new setup brings in terms of stability…

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6 Responses to Eliminating errors in temperature control

  1. Jeroen says:

    Hi Robert,

    You say that you don’t want to move the living room thermostat. But now you’ve disabled it and are using the external one. What is the principal difference?

    Does the MAX! not have a remote sensor?

    Regards, Jeroen

    • The difference is that the thermostat is still in the living-room, where everyone expects it to be. Now I can put the temperature sensor wherever I want – for example under the stairs in the hallway, or maybe even somewhere upstairs or in the kitchen; no limitations.

      The MAX! radiator thermostats seem to send the temperature sensor values as well as I found out very recently, but I’m not sure yet if those values are really that usable. It’s on my todo list 😉

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  4. David Pritchard says:

    I’m embarking on a major refurbishment and aiming to have a similar set-up: radiant floor heating with multiple zone control.

    The current idea is to have several multiple thermostats. A master thermostat controls the boiler temperature, and the others open or close the valves for their zones, as needed.

    Originally I wanted the Nest thermostat (because it’s smart enough to take into account such things as the weather), but then I was told I need a modulating boiler for efficiency, which in turns means a modulating thermostat. So I tried to find a “smart” modulating thermostat – in turns out such beasts are rare indeed. So rare, apparently, that they only exist in the Netherlands – the centre of the universe for modulating boilers and thermostats. 🙂

    So now I’m considering the ThermoSmart as the master thermostat, in spite of the fact that it’s in Dutch. The guy who installs it will have a fit. 🙂 Do you know anything about this thermostat?

    • Robert Hekkers says:

      I’ve read about the ThermoSmart but never used one myself. Funny, when I visited their website to refresh my memory I saw that their HQ is less than 10 km away from here 😉

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