Running the heating as efficiently as possible and with low gas consumption has been important to me not just since the gas crisis. Not because we couldn’t afford it, but because it’s simply stupid to burn gas unnecessarily. That’s why, since we moved in in 2018, I’ve been constantly tweaking the heating settings, observing the behavior and further optimizing it, because the heating company’s settings were simply wrong. I’ve now reached a point where there are hardly any optimization possibilities left, because I’ve been able to reduce the average annual consumption of previous years by 34 percent.
Important: I can only present my experiences here and cannot offer ready-made solutions. Systems, houses, insulation, usage and preferences are too different.
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Our house, our heating
Our house was solidly built in 1964 and completely renovated between 2016 and 2018. The floors came out and underfloor heating went in, and since a gas connection had already been laid into the house by the previous owners, a Viessmann gas condensing boiler was the heating of choice, as both the unit and the gas were very affordable. The heating was supplemented by a fireplace with water circulation, with which the entire house can be heated and domestic hot water can be produced. There is also a large buffer storage tank in the utility room that can absorb the heat from the fireplace and gradually release it to the heating system.
In addition, our house was equipped with large floor-to-ceiling, triple-glazed windows on the south side and moderately insulated (12 cm). The temperatures of all rooms can be recorded via the LCN-Issendorff building automation , Home Assistant and our own sensors.
Optimally setting gas boilers, hydraulic and thermal balancing
I noticed early on that the heating company that planned and installed our system does little to ensure that the heating is also well adjusted. This wasn’t a small business, but a company with 40 employees. However, a heating system in a single-family home is simply always oversized so that there are no complaints later that it wouldn’t get warm. What is missing are adapted parameters and a real hydraulic balancing based on practical values and not just theoretical design regarding pipe length, flow resistance, estimated heat demand per square meter, etc. After hydraulic balancing comes thermal balancing . At the latest here, the heating engineer is out, because the framework conditions have to be right and he is guaranteed not to be in the house at the right time.
The heating technicians also don’t dare to go into the deeper service levels of a modern heating control system, let alone know what the individual parameters do. Only a field service employee of the heating manufacturer knew about this and caused question marks in the eyes of the heating technicians present.
“Service level 2? We don’t touch that, hehehe!”. The field service employee of the heating manufacturer was able to properly explain my heating system to me for the first time and gave valuable tips. However, he also told the two heating technicians present that they should very well be familiar with it and deal with it.
The field service employee told me that heating engineers do specify a hydraulic balancing on paper, but this rarely fits. The reason for this is also obvious, because hydraulic balancing is followed by thermal balancing of the system and this must be done at different outside temperatures, readjusted several times and, due to the inertia of underfloor heating, also takes a long time. In addition, you simply have to test whether you achieve the feel-good temperature in the respective room with the settings.
The purpose of hydraulic balancing is that each room receives just the amount of heat it needs for the desired temperature. If a room doesn’t get warm, the flow temperature of the heating is often simply raised. Problem solved - for the heating engineer. Now the room gets warm and the other rooms get even warmer and you consume energy unnecessarily. But the heating engineer doesn’t pay for that. He even sends us a bill for this “service”.
“Service level 2? We don’t touch that, hehehe!”
- Heating technician on site
We also decided against individual room control (ERR) with thermostats in our house. In well-insulated houses, the room temperature can be regulated entirely without thermostats, solely through hydraulic balancing. This has the advantage that external heat input from solar radiation on the floor (with underfloor heating), waste heat from devices, etc. is also transferred to other rooms and a self-regulating effect also occurs. This is nicely explained here: http://www.bosy-online.de/Selbstregeleffekt.htm .
This works perfectly for us and led to the first savings in the range of 15%. Moreover, the actuators of underfloor heating systems themselves consume electricity (approx. 1-2 watts per valve), which would mean a power consumption of 60 watts for us, just for the heating actuators, and that for about 200 days a year = 288 kWh of electricity - at current electricity prices, that’s 100 € per year. The power consumption of the control system and room thermostats is not even taken into account here.
In modern houses, individual room control is nonsense, costs money during installation and in operation. Hydraulic balancing only costs time and is more efficient. Its optimal effect is stifled by individual room valves.
With the correct setting of the heating curve and the heating times, you have a big lever when it comes to consumption optimization. This is also a setting that is only done by eye by heating engineers. If you want to optimize your heating, you have to deal with the subject yourself, document the settings and effects made and “experience” them. The heating engineer is only in the house for a few minutes and makes his standard setting, which can never be optimal.
Our time program for normal underfloor heating operation only runs from 6 to 8, 11-13 and 17-21 o’clock. With this, we have found an optimal value between the inertia of the UFH and constant room temperature. However, we only lower it by a maximum of 2 degrees in between. My measurements have shown that a higher night setback increases energy consumption, as the screed cools down too much and this has to be made up for with more energy.
Domestic hot water temperature and circulation
A lot of energy is wasted on domestic hot water preparation. The domestic hot water is heated to the setpoint temperature too often, which is also set far too high. The basic setting of our heating was 65 °C hot water temperature and practically permanent preparation between 5 a.m. and 11 p.m.! At the same time, the program for the circulation line was also constantly active during this time. Hot water circulation in particular destroys enormous amounts of energy, as the heat loss must be constantly compensated.
We now only have 48 °C hot water setpoint temperature and a single heating at 6 a.m. The circulation starts at 6:30 a.m. and at 10:30 p.m. for half an hour each - that’s it! With this, we have enough hot water for 24 hours, even for a shower in the evening.
In the dreaded parameter level 2 of our Viessmann heating control, you will find parameter 59 “Storage heating: Switch-on point setpoint”, which can be set from 0 to 10 K(elvin). The default setting was 4 K. This means that the domestic hot water heating starts immediately if, during the active hot water program, the temperature drops 4 K below the setpoint. However, 44 °C is still sufficient, which is why I set this parameter to 8 K. This has the effect that domestic hot water heating often only takes place every 2 days, because even after more than 24 hours, the domestic hot water temperature is still over 41 °C.
However, another problem appears here: The temperature for this parameter is measured in our buffer storage tank at about 2/3 of the height. In fact, the temperature of the top layer, from which the hot water is also drawn, is still at 48 °C when the sensor only measures 35 °C.
With these settings, we were able to reduce the energy consumption for domestic hot water preparation by 2/3!
You don’t need to worry about legionella, which is often cited when running low domestic hot water temperatures in single-family homes. Our tapping points are regularly in use, so legionella cannot form here, and we also don’t belong to the risk groups. A “hygiene program” also heats the storage tank to 65 degrees every 10 days. But this only helps if you then let all hot water pipes flow and flush for some time.
Quick guide to heating optimization
- Read up on the subject and do research. Sites like https://www.haustechnikdialog.de , https://www.heizungsforum.de/ or the forums of the heating manufacturers usually help better and more competently than the local heating engineer.
- Hydraulic balancing of the system - the be-all and end-all of heating optimization, but must be “experienced” ? Thermal balancing
- Optimize heating curves
- Reduce heating times, in summer only hot water operation
- With underfloor heating, dispense with individual room control (which should no longer be a problem thanks to hydraulic balancing)
- Measure and record room and outside temperatures (easy and convenient with a smart home control system)
- Document all changes. Take photos of the settings on the heating control.
- Reduce domestic hot water temperature. Depending on usage and number of users, 48 degrees may be sufficient.
- Reduce domestic hot water heating cycles. Depending on the system and usage, 1-2 heating cycles per day are sufficient.
- Reduce or deactivate circulation
- Further optimizations by adjusting the “deeper” heating parameters
- Use smart home technology for control based on usage and presence
Further optimization through Home Assistant
Yes, you could say that we have a very smart smart home. Home Assistant helps a lot with this. For most modern heating systems, there are already ready-made integrations for Home Assistant. This is also the case for our Viessmann heating with ViCare module. With this, you can not only read out the gas consumption, boiler and flow temperatures or the hot water temperature, but also control the heating circuits. When we leave the house (no smartphone logged into the WiFi anymore), Home Assistant switches the heating to reduced operation. And when the most important rooms in the house have reached a temperature of 22 °C (e.g. due to waste heat from cooking or solar radiation), Home Assistant switches off the heating circuits.
I can also monitor the entire return temperature via a sensor (see my project here: /mein-neuer-esphome-multisensor-mit-display-fuer-home-assistant/ ) and when this is equal to the flow temperature, i.e. no more heat can be delivered to the rooms, the heating is also switched to reduced operation. My control does this significantly earlier than the actual heating control.
However, the really big advantage of Home Assistant is that I can record and compare all parameters of the heating, room and outside temperatures over long periods. This provides the optimal basis for optimizations and allows you to really assess whether they have brought anything.
The energy demand this year will be 15,000 kWh for heating and hot water, although some major optimizations, such as the additional control by Home Assistant, were only added in May 2022. So it may well be that the savings in the coming heating season will be even more significant. The average of previous years was about 23,000 kWh.
Conclusion
One of the biggest levers for saving energy - not only with gas heating - lies in the correct setting of the system, and that outside of standards such as heating curve and heating times.
Unfortunately, it turns out that many heating companies still work according to a cookie-cutter approach and have little knowledge of modern heating controls. Not to mention the knowledge for the design and setting of heat pumps. An acquaintance from the industry told me that in the training of heating engineers, just 8 school hours are available for heat pumps and hardly any vocational school even has heat pumps available for practical training. A look at the framework curriculum for plant mechanics for sanitary, heating and air conditioning technology (Bavaria) shows that the term “heat pump” only appears once in a subordinate clause here (page 32).
The problem is exacerbated by the fact that there is hardly any new talent, as a customer you now stand there as a supplicant and can hardly hope for timely service. It’s already gone so far that you only get appointments earlier for a fee or they want advance payment.
To avoid any misunderstandings: I don’t want to tar the entire heating trade with the same brush. There are certainly excellent and competent people here, as can be seen not least in the relevant forums. However, my experience is that there is hardly any interest in more targeted settings and they only know the most rudimentary things - the main thing is that it gets warm and no one complains. It would certainly be interesting what specialists would say about the design and setting of the systems if you were to simply select 10 systems at random …
That’s why you should teach yourself the basics. On the one hand, this has the advantage that you can save real money with your own observations and optimizations. On the other hand, however, also that you no longer stand there blankly when a heating engineer does find time.
EnSimiMaV - Medium-term energy supply security measures ordinance
From October 1, 2022, a mandatory heating check is to be introduced if you operate a gas heating system. Although the law has not yet passed the Bundesrat, one can probably assume that it will come.
Officially, the bureaucratic monstrosity is called: Medium-term energy supply security measures ordinance - no joke! A few hyphens would at least make it readable. But this word also immediately reveals whose spirit child it is.
As I described above, even heating technicians have problems determining and setting the real energy-saving factors of a heating system in operation. But now chimney sweeps and energy consultants are also supposed to determine whether the heating is correctly set. Although the draft of the ordinance also states that pipes should be checked for correct insulation, etc., which I also trust these people to do. However, I consider all other matters to be completely pointless.
Whether a night setback makes sense or perhaps even leads to increased consumption cannot be said in general terms. I would also like to see how “good” and “bad” are argued when it comes to setting the heating curve. I already wrote about hydraulic balancing above. It’s on the heating company’s invoice, but is only a rule-of-thumb setting. Heating curves can look “good” and the heating can still be set incorrectly. Our heating has over 100 setting options on both parameter levels. And once the inspector is out of the house, I can set everything back the way it was before - or worse …
Exceptions to the EnSimiMaV? Yes, but nebulous.
Interesting is the sentence under § 2 (5) “The obligation for the heating check is waived in buildings that are managed within the framework of a standardized energy management system or environmental management system and in buildings with standardized building automation”.
What on earth is supposed to be standardized building automation? KNX KNXWired bus system for building automation (since 1990). Professional standard using twisted pair cabling. Home Assistant has had an official KNX integration since 2023 ? LCN LCNLCN (Local Control Network) – German bus system for building automation by Issendorff. Uses existing 230V wiring as bus line. Can be integrated into Home Assistant via LCN-VISU or custom integration Issendorff? Homematic? Home Assistant (at least the most widespread) or a protocol like BACnet or Modbus and where can I assert this?
What about homeowners like me, who, through comprehensive and verifiable measurements AND building automation, have optimized the heating and its consumption in a way that is hardly possible even for professionals and can prove the successes in numbers?
The costs for this EnSimiMaV EnSimiMaV check are supposed to be between 100 and 150 € - without any further work. If someone comes to me and thinks they need to change something about my settings, I would probably pursue a lawsuit for the first time in my life.
It is of course sensible to optimize the heating - not only because of the gas crisis. I’ve been doing that for years. But the design of this new obligation is simply nonsense. It doesn’t distinguish between new and old systems, leaves questions about the minimum competence of the inspectors open and doesn’t define what is to be regarded as “standardized building automation”. An effectiveness check is also missing. This would be difficult to argue anyway, since the same framework parameters such as outside temperatures, same usage, etc. would have to be used as a basis.
Apart from that, it should be difficult to find a specialist company. Oh yes: The deadline for implementing the Medium-term energy supply security measures ordinance is September 15, 2024. Let’s hope that this nonsense is still stopped in the Bundesrat.
Hi! I'm Markus – the Fricklr. ⚡ Electrical engineer, 🎵 musician (bass, guitar, keys) and professionally 'something with the internet' 🌐 for over 30 years – nowadays with AI too 🤖 – a 55-year-old generalist from Bavaria, Germany.
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