ᐅ Heat pump is not compatible with a hydronic (water-heated) fireplace.
Created on: 20 Oct 2023 18:54
J
Jessica388
Hello everyone,
I hope someone here can help us because our heating engineer doesn’t seem to be able to…
Key data
New build 2022 with 250 m² (2,691 ft²)
Heat pump Viessmann Vitocal 200-A
Multifunction storage tank MFS1000S
Water-heated stove with heating capacity on the water side of 8 kW
Photovoltaic system
Electric heating element
I am attaching the schematic of the storage tank layout.
The stove was initially connected under “old” and now it has been modified.
Everything works fine as long as the underfloor heating is off.
When the underfloor heating is on, our hot water temperature doesn’t exceed about 55°C (131°F).
When the underfloor heating is off, the temperature ranges between 65–75°C (149–167°F), either via the electric heating element during sunshine or by stoking the stove.
Now, however, this energy seems to be wasted. It can’t be that the underfloor heating requires 70°C (158°F) supply temperature to achieve a flow temperature of 35°C (95°F), right? The return water is only slightly cooler. So the water should only need to be heated by a maximum of 5°C (9°F).
We assume either a) something is still connected incorrectly, or b) the cold water from the underfloor heating causes such circulation that the hot water cools down within minutes.
What can be done about this?
Has anyone experienced similar problems?
Normally, we should almost run without electric power, but currently the heat pump switches on almost every hour to heat hot water…
I hope someone here can help us because our heating engineer doesn’t seem to be able to…
Key data
New build 2022 with 250 m² (2,691 ft²)
Heat pump Viessmann Vitocal 200-A
Multifunction storage tank MFS1000S
Water-heated stove with heating capacity on the water side of 8 kW
Photovoltaic system
Electric heating element
I am attaching the schematic of the storage tank layout.
The stove was initially connected under “old” and now it has been modified.
Everything works fine as long as the underfloor heating is off.
When the underfloor heating is on, our hot water temperature doesn’t exceed about 55°C (131°F).
When the underfloor heating is off, the temperature ranges between 65–75°C (149–167°F), either via the electric heating element during sunshine or by stoking the stove.
Now, however, this energy seems to be wasted. It can’t be that the underfloor heating requires 70°C (158°F) supply temperature to achieve a flow temperature of 35°C (95°F), right? The return water is only slightly cooler. So the water should only need to be heated by a maximum of 5°C (9°F).
We assume either a) something is still connected incorrectly, or b) the cold water from the underfloor heating causes such circulation that the hot water cools down within minutes.
What can be done about this?
Has anyone experienced similar problems?
Normally, we should almost run without electric power, but currently the heat pump switches on almost every hour to heat hot water…
B
Buchsbaum21 Oct 2023 20:46This has become quite a complex case, with numerous expert opinions.
What do we know about the specific situation? The electricity consumption is extremely high at 65 kWh per day. And this is not even during the cold season.
There is much more that we don’t know. For example, how large is the photovoltaic system? Is it a photovoltaic heating rod with direct DC connection? What is the daily hot water consumption? How many people live in the house?
Is it a room-air-independent fireplace with external air supply?
The problem lies with the buffer tank, not your heating system. Mistakes were made here.
The heat pump should have its own heating circuit. The photovoltaic system can effectively support the heat pump. Your fireplace can be useful for hot water generation. Running all three together through one buffer tank is generally complicated.
If in doubt, contact the technical service of the buffer tank manufacturer. Explain your problem to them. There will certainly be solutions.
Of course, the fireplace and the water circuit should remain. This way you stay flexible and independent. You can also separate the heat pump’s heating circuit from the buffer tank. Then it will operate normally at first.
What do we know about the specific situation? The electricity consumption is extremely high at 65 kWh per day. And this is not even during the cold season.
There is much more that we don’t know. For example, how large is the photovoltaic system? Is it a photovoltaic heating rod with direct DC connection? What is the daily hot water consumption? How many people live in the house?
Is it a room-air-independent fireplace with external air supply?
The problem lies with the buffer tank, not your heating system. Mistakes were made here.
The heat pump should have its own heating circuit. The photovoltaic system can effectively support the heat pump. Your fireplace can be useful for hot water generation. Running all three together through one buffer tank is generally complicated.
If in doubt, contact the technical service of the buffer tank manufacturer. Explain your problem to them. There will certainly be solutions.
Of course, the fireplace and the water circuit should remain. This way you stay flexible and independent. You can also separate the heat pump’s heating circuit from the buffer tank. Then it will operate normally at first.
J
Jessica38822 Oct 2023 09:38RotorMotor schrieb:
That’s just the household electricity consumption.
Or where do you see anything showing the heat pump’s consumption?
The heat pump keeps having peaks, which is also called cycling.
It simply can’t release the heat because 90% of the rooms have their thermostatic valves almost closed.
Lower the heating curve to 0.4 and open the room thermostats, then we’ll check back in a month. ;-) @RotorMotor @Mycraft and of course good morning to everyone else!!!! Last night was great!!!! The heating engineer can hear it, and I want to thank you all sincerely.
Comparison between yesterday and last night.
We’re super satisfied, what do you think?
Any more tips?
R
RotorMotor22 Oct 2023 11:54Those are already some good news!
Now, it might be necessary to wait and see how the temperatures behave inside the house.
Will it become uncomfortably warm or cold in certain rooms or even throughout the entire house?
If so, adjustments will need to be made specifically to the heating manifold or the heating curve.
Now, it might be necessary to wait and see how the temperatures behave inside the house.
Will it become uncomfortably warm or cold in certain rooms or even throughout the entire house?
If so, adjustments will need to be made specifically to the heating manifold or the heating curve.
J
Jessica38822 Oct 2023 12:24RotorMotor schrieb:
That’s already good news to start with!
Now you might need to wait and see how the temperatures behave inside the house.
Will it get uncomfortably warm or cold in certain rooms or even throughout the whole house?
If so, you will need to make targeted adjustments to the heating circuit distribution or the heating curve. Understood. We are also very curious to see how it performs in colder weather and whether the stove will actually warm the water or if the energy just goes into the floor again.
When it gets cold, I can first try raising the desired room temperature, right? Because at 19°C (66°F) the setpoint was already quite low, wasn’t it?
1. Adjusting the heating system is a time-consuming process.
2. It’s not something that can be done just once.
3. Every autumn before the heating season, I go down to the basement and check every setting—mainly to make sure everything is still working.
4. Efficiently setting up the heat pump is not the job of the heating technician, but designing the system is.
Last year, for example, the return temperature sensor and the outdoor sensor were faulty and had to be replaced.
Currently, the heating is behaving just like last year. Today, as a test, I increased the heating limit to make sure the heat pump actually turns on.
It’s not like in a rental apartment where you just turn up the thermostat and call the landlord if it’s too cold.
2. It’s not something that can be done just once.
3. Every autumn before the heating season, I go down to the basement and check every setting—mainly to make sure everything is still working.
4. Efficiently setting up the heat pump is not the job of the heating technician, but designing the system is.
Last year, for example, the return temperature sensor and the outdoor sensor were faulty and had to be replaced.
Currently, the heating is behaving just like last year. Today, as a test, I increased the heating limit to make sure the heat pump actually turns on.
It’s not like in a rental apartment where you just turn up the thermostat and call the landlord if it’s too cold.
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