First of all, I am not a heating professional, refrigeration technician, or anything like that, so please keep in mind that any adjustments you make to the control system are at your own risk.
Happy New Year and no, I haven’t forgotten you, I just noticed that the information you gather over two years can’t simply be condensed without taking some things out of context. I caught myself that when compiling the design criteria from the general contractor and myself alone, I already come up with 4-5 DINA pages, and that really only covers heating loads, outdoor temperature, room temperature, etc.
So here’s your summary in principle: I am satisfied with the system, it does what it’s supposed to do, namely keep the house warm.
Here are some pros and cons:
I find the menu navigation of Vaillant quite annoying or unclear.
For example, there are two levels for professional installers, one located in the Multimatic, the other in the VR71 or whatever the small display is exactly called.
In the Multimatic, there are more or less the settings that can still be entrusted to the end customer, like heating times, room temperatures, hot water temperature, heating curve, heating element, bivalence point, etc., so more or less the basic configurations.
The small display is aimed more at the professionals or more experienced operators of the system—here you should be very careful about what you adjust because you have access to compressor hysteresis, compressor current limitation, whisper mode, etc. So keep your eyes open and don’t just press buttons arbitrarily.
Generally, my 3.5 kW system, which is still suitable in relation to the heating load, is oversized for the transitional period (roughly 0°C to 12°C outdoor temperature). (Here the first 4-6 pages would come into play.) I proceeded as follows:
Heating element deactivated or its activation point set to -12°C, which is more or less the normal outdoor temperature, although in spring 2021 we had -13.9°C once.
I’m still experimenting with the heating curve; the heating system is more or less a hobby of mine, which also has professional background.
Currently, I run a heating curve of 0.15 or 0.20.
To prevent short cycling during the transitional period, I set the compressor hysteresis to the maximum of 15K. This means that the determined/measured/actual flow temperature can exceed the calculated flow temperature (e.g., according to the heating curve) by 15K before the compressor is switched off, unless the control system switches off the system earlier.
The Vaillant control works via the energy integral, which means it compares the target flow temperature (as per the heating curve) with the actual flow temperature (i.e., temperature not delivered or ideally delivered). The system detects whether heating power is needed (actual flow temperature ≤ target flow temperature) or if the house is warm (actual flow temperature ≥ target flow temperature).
In the background, the so-called degree minutes then go up or down; these can also be adjusted in the control system on the left, set by me from 60°C minutes to a maximum of 100°C minutes.
The system starts or stops at 0°C degree minutes. 0°C means no heating demand because the actual flow temperature is above the target flow temperature. If it is the other way around (actual flow temperature lower than target flow temperature), the system counts down in real time and difference between target and actual flow temperature to a negative range, e.g., -100°C minutes, and then switches the heating on at -100°C and tries to drive it back toward 0°C minutes by raising the actual flow temperature until it is higher than the target flow temperature due to no heat demand. The goal should be to keep the difference between target and actual flow temperature (the heating curve comes into play here again) as low as possible to reduce cycling.
By now, I believe I understand that a heating curve set too low can also contribute to cycling because the minimum power of the heat pump (in my case from 0°C to 0°C) is already so high that, e.g., for a heating curve of 0.10 or 0.15, which calculates a flow temperature of about 23-24°C from 0°C to 10°C, the actual flow temperature increases too quickly since the system is delivering at least 24-25°C flow temperature even at the lowest limit.
Therefore, I experiment with the base point of the system (minimum heating circuit temperature in the Multimatic) and have set it to 25°C.
This forces the system to start with at least 25°C flow temperature until the heating curve demands a higher temperature. This might be nonsense; it’s still theoretical for now.
At the same time, you can influence the upper curve of the heating curve via the max temperature, in my case 30°C, as the underfloor heating is designed for this maximum temperature.
There is also a desired temperature, which can be set via a rotary knob in the Multimatic, but this causes a parallel shift of the heating curve, which I don’t want because depending on the setting, e.g., a 0.10 curve that ends at 30°C flow temperature at -12°C also increases the maximum flow temperature depending on the set room temperature and not just the base point.
The system’s power consumption averages 0.5-0.7 kWh depending on outdoor temperature; currently, the max is 10°C and min is -8°C; it hasn’t been colder this heating period yet. The annual performance factor for heating displayed is somewhere between 4.5 and 5, but I am still fiddling too much with the system.
In the end, it’s enough for me to see that I had a total electricity consumption of just under 4400 kWh per year for the entire household and heating and fed about 7000 kWh into the grid with my photovoltaic system. We don’t stress ourselves about that either, meaning the washing machine, dryer, dishwasher, or infrared cabin, etc., also run at night if needed. We do not schedule our daily routine according to the photovoltaic system.
What we could still optimize is the ventilation behavior; this would certainly allow for some improvements in heating and temperature level, but the government is firmly convinced that window tilting ventilation is not counterproductive. Warning: irony. “Because the air coming in through tilted windows is fresher than the air supplied by controlled residential ventilation.” I’ll leave that as is; everyone has their own view on that anyway.
If you have specific questions about individual menu items, please ask directly, otherwise this will get too extensive and my post would become even longer.
I deliberately did not go into the parameters for hot water because we A: indulge in the luxury or the criticized energy loss of a circulation line and B: the storage temperatures and time releases have to be set individually anyway.