Gas consumption under the microscope

I’m not really satisfied with how our Central Heating is functioning. Not that we have technical problems, but the way our house is heated isn’t satisfactory anymore. Maybe it has to do with the floor heating we installed earlier this year; I don’t know for sure – I guess it does, but to make the right conclusions, I need more information.

For example, here’s the chart for the central heating of December 24th & 25th, where you can see at what times and for how long it’s heating the house:

Why is there such a big heating interval in the afternoons? What’s the most important factor, outside temperature or the amount of sunlight? (the latter is definitely of influence cause the living room has a window on the south, measuring 2 x 3 meters…)

Looking at the right side of the chart below, we see the temperature in the living room (the red line) rising to 21.7 °C without any heating (green = thermostat setback):

Free energy from the sun; that’s very nice, but not good for keeping the rest of the house warm.. 🙁

I really need to create some more insight on all of the factors that influence the behavior of the central heating system.

So that’s what I am doing right now. I’ve added some virtual devices to my Domotica system to calculate some additional values from all the sensors I have.

  1. Break down total gas usage into 2 parts: gas usage for CH (Central Heating) and for DHW (Domestic Hot Water). I can do this cause my Remeha Calenta tells me whether there is DHW demand or not. This should give me a clearer picture of the amount of gas used for heating; ‘noise’ by someone taking a bath or a shower will be filtered out.
  2. Average Outside Temperature per day. For this I compared measurements from the nearest KNMI weather station (12 km) with my own outside temperature sensor and didn’t see a need to collect the weather data from KNMI, saving me some additional work. I’m going to use my own sensor for this. This sensor is probably not located at the right height, it’s mounted to a wall of the garage etc. which will result in an offset, but it should be good enough to use.
  3. Average light intensity in the living room; I have a Lux sensor in the living room and I’m going to use this one to monitor the average amount of light there.

These values should give me a more detailed view of what is happening and how much the influence of both outside temperature and sunlight really is; I know they do, but not how much..

With this I want to be able to explain the behavior of the central heating and explain the gas usage that comes with it.

I started  a webpage to do just that. It’s not finished yet; more information will be added like the weighted average of the thermostat setback during a day, average temperatures in the ‘other’ rooms and things like that.

What I really want, is being able to control the temperature per room: the bedrooms, bathroom, my office and the living room. That’s a total of 6 rooms. Looking at how much sunlight influences the central heating, I need a way to deal with that influence; but how? I will probably need to control the amount of heat flowing through the floor heating based on the temperature in the living room, cause when another room is demanding heat, I don’t want heat pumped into the living room when it’s already warm enough!

And I probably also need to control the radiators in the other rooms to get the right temperatures over there, cause I have the feeling that too much heat is going to the living room right now, leaving too little for the other rooms. But first, that feeling has to become a conclusion before I can move forward!

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8 Responses to Gas consumption under the microscope

  1. Patrick says:

    Hoi Robert,

    I have been thinking about similar issues and thinking of similar targets (control the temperature per room with the least possible energy loss).
    The only way to lose heat is through the walls and windows. Walls being the major part in my opinion. By the time the cold gets into the room (through the wall) you’re in my opinion too late. You should start heating before the (outside) wall is getting cold. I’m still thinking of an option to measure the temperature in different depths in the wall and on all 4 sides of the house. It’s theory but I’m curious if I can get somewhere with this.
    I live in Poland. Large house, thick well isolated walls and huge temperature differences. I can control each heater from a central point which makes things easier. There should be a lot of energy to save.


  2. Kris Lee says:

    Now tell me, do I understand correctly that what you want to do is controlling individual room temperature without controlling individual room temperature?

  3. Kris Lee says:

    You said that “I will probably need to control the amount of heat flowing through the floor heating based on the temperature in the living room, cause when another room is demanding heat, I don’t want heat pumped into the living room when it’s already warm enough!”

    I read from this that you only want to have only one thermostat. Do I miss something? Because usually each room does need individual termostat and individual control valve(s). This is also usually an easiest way to take additional heat from the sun into the consideration. But I do know know how it would work with the floor heating because it is usually kind of slow. So maybe you could use short therm weather forecast when something like this is available for your location?

    I think that in your special webpage you have to show also the room temperatures because the gas usage does not give you the whole picture specially when you control your heating based on one thermostat only.

  4. That’s not what I meant. Currently I do have only one thermostat, but that doesn’t mean that will stay that way. In the 14 years we live here, having 1 thermostat has never been a problem; all the rooms were heated well, even with 1 thermostat; there must have been some sort of balance in the whole system before the floor heating. That has changed now (no more balance).

    So when one of the other rooms demand heat, I (now) want to be able to lower the heat going through the floor heating if it’s not needed there, probably with a valve, or maybe shutting down the pump will do, I don’t know yet. It’s all still a bit blurry to me, but I do think I need more than 1 thermostat in the future. I just didn’t vent that yet 😉

    The webpage I created was done during Christmas with very little time, it’s only a start and more will be added in the near future. My goal is to have everything fixed next autumn.

  5. Henk says:

    Hello Robert,

    If I look at your graph’s ( I don’t see a difference between day and night. And more important I don’t see modulation it looks like your central heating only switch on and off. I think if you tune your thermostat PID settings, your setpoint will be held more accurate and your central heater can operate on a lower temperature.

    • You’re right twice; the thermostat is set for 20.5 degrees 24/7 this week. Next week the thermostat (and “we”) go back to the normal schedule.
      The thermostat I currently use is a Proliphix NT20e, which is an on/off type.

  6. Henk says:

    Hello Robert,

    If you still have your old modulation thermostat I would give that a try. Because this will result in a more accurate and faster regulation and a lower gas consumtion (lower water temperature will give a better efficiency), you can check it directly by monitoring the Remeha and your gas ussage.

    Good luck


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