Tomasz Korwel
programmer, administrator, engineer - my everyday fights with reality

Looking at the graph (and trying to keep my fingers from freezing):

I noticed interesting thing - the temperatures in my office tend to go down a bit every day (look at those last four green peaks). Keep in mind that my thermostat is set to the same temperature as it was before, yet those temps really go down. Looking for explanation I tried to remember what changes in weather did we observed during those last 4 days. Did it become colder outside? Not really. Maybe hotter? Naa… Rained? Snowed? Was it windy? And then it strike me - we got more and more sun each day. So apparently upper level of our house acts as greenhouse absorbing energy from sun. And because the thermostat is in fact mounted there, lover level rooms, not exposed to radiation heat became colder and colder.

One additional reason why giving those rooms more decision power as when to turn the furnace on is not that bad idea.

I installed 2 motorized registers and set the system to run in passive mode.

Here you can see:

how it nicely flattened the temp curve by closing the registers when temperature reached setpoint.

Time to finish the rest of the house.

A comment posted under one of my older posts reminded me that it can be a good idea to resurrect and finish my HVAC zoning project I shelved some time ago. Main cause I did so was that I couldn’t get dz compiled. I didn’t have time to mess with it any longer then, but I decided to give it a try this time. It turned out that over last two years Ubuntu project went forward so much that this time dz compiled successfully the very first time I tried. So right now I have a spider web construction on my desk consisting of two 1-wire temp sensors and two servos run by phidget boards. And they work. Servos are opening and closing according to changes in the temperature of my office. They have no influence as they aren’t running registers yet, but they proved to work. Now it’s time to run wires around the house and motorize registers.

Stay tuned.