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Author Topic: Raspberry Pi Heating Controller  (Read 325 times)
Stig
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« on: October 29, 2018, 11:32:15 AM »

I recently installed one of these:
https://www.instructables.com/id/Raspberry-Pi-Home-Heating-Controller/  *

and it's working rather well.  Big improvement on the mechanical 24hr timeswitch - I can have different settings for weekends, week days, working-from-home days, holidays etc. - and I didn't have to change the clock for GMT as it does that itself!


*Actually it's the modified version here:
https://github.com/jonsag/pi-heating
with a direct-wired temperature sensor.

I even tweaked the code slightly so it now advances the turn-on time according to how cold the house is so I just set the schedule to 'I want it to be warm by this time'.

I even get a pretty graph showing what temperature the house has been over the last day/week/month etc.  Smiley

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kristen
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« Reply #1 on: October 29, 2018, 12:32:49 PM »

Very interesting, thanks.

I need to get on with starting my own project ... but I have so little knowledge of Systems Control, and not enough tinker-time ... so starting from a simple point would certainly help.

I have:

  • Thermal Store, single circuit (a pump) to CH Rads.
  • Light boiler, guess how long the CH should run, set timer. Typically 6 hours will mean CH is on for 6 hours and at the end house will be warm Smiley and Thermal Store will be at 90C at the boiler goes out
  • Then tomorrow morning I'll put the timer on for a bit ... and light the boiler in the afternoon to repeat the cycle
  • I also have a single thermostat which will bring the pump on (in addition to the timer) but no point if it doesn't know what temperature the Store is

So sounds like I could just replace that with the Pi Smiley

and then I would have:

Mimic Thermostat / Timer to bring Pump on. Do that for a timetable schedule, and depending on temperature of the Store, and possible External / Weather.

Something I urgently want is temperature sensors to LOG the date/time and temperature in all the rooms, and the Store temperature, and whether the pump is running or not. I have CAT5 sockets everywhere, so would like to exploit that for temperature sensor logging. Armed with historical data I could (in future) program the function of the system much better.

I could then look at Phase 2:

  • Predict when I'll need to light the boiler.
  • Allow me to say how much fuel I have put in (Full burn / Half burn) and run the pump for appropriate amount of time.
  • If pump off, boiler still running, and Store approaching 90C then turn on CH to dump heat

if I got somewhere near that wishlist, over time, I could then move on to trying to control the UFH in the new bit:

  • Replace Thermostats in each room with Temperature Sensors
  • Open UFH valves as necessary.
  • (Mostly its a pump-run-time thing, the lag for UFH to raise the temperature by 1C is huge, and once it has done THEN turning it off will be too late - there will be masses of heat in the slab by then, and the house needs almost-no-heat)

Then i can fiddle with:
  • If its "cold" run the UFH in the bog "regardless"
  • Is it SO cold outside that I need to turn the UFN on in Conservatory to keep the plants alive?

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Stig
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« Reply #2 on: October 29, 2018, 02:45:52 PM »

It looks like this would be a useful starting point for you.  I haven't fully figured out how the Python code works but understood enough to add my little turn-on adjustment (I've never seen Python before but am familiar with C).

What you can do with the basic system is set up modes, timers and schedules as well as input sensors and output devices (relays).  A schedule can be dependent on mode, timer and temperature as well as its own start and end times so you could have something like:
if temp<21  and  mode=fred  or timer1=running  then  turn on relay1

My schedules are generally like:
if  temp<21  and  timer_holiday=stopped  then  turn on relay

I've only got one temperature sensor but you can add several and make things dependent on one or more of them.  You could use the existing CAT5 cables for sensors (needs 3 wires) or they could be wireless each with their own little Pi Zero.
I guess if your system needs manual input (lighting a fire etc.) then you could wire, say, a light to another relay output as a signal to tell you to light the fire if you don't want to be checking the app on your phone all the time.
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kristen
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« Reply #3 on: October 29, 2018, 06:18:59 PM »

Thanks. That sounds really promising. I'm a programmer by profession, so the programming bit should suit me Smiley
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Greenbeast
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« Reply #4 on: October 29, 2018, 06:49:27 PM »

Sounds cool,

I remember trying to do a DHW controller with an arduino before, that was fun even if it never got put into action.
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