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…
J
Jessica38821 Oct 2023 13:51Mycraft schrieb:
But there must still be a calculation of the primary energy demand, etc., in the house documents.No, that wasn’t done either, at least we don’t have anything like that. Because someone requested it once before.R
RotorMotor21 Oct 2023 13:56Jessica388 schrieb:
@RotorMotor do you think the chimney connection is better like this? Or the previous version? With the old setup, we had the problem in winter that the temperature in the buffer tank didn't rise, but it was almost unbearable in the living room. That’s why we wanted this modification.Phew, good question. I’m much more familiar with heat pumps than with fireplaces. I’m not a big fan of them either. Today we were also annoyed by the neighbors who smoked everything up here...Basically, I believe the connection was better before than it is now.
The real question, as Mycraft already said, is how the underfloor heating is connected.
And especially, did you set all the room thermostats to level 1? You should know that as soon as the temperature set on those is exceeded, they completely shut off the flow. So, that’s not a regulation but just an on/off function. How is the heat supposed to be transferred from the fireplace to other rooms then?
Energy performance certificates have been mandatory since 2002, right?!
J
Jessica38821 Oct 2023 14:02RotorMotor schrieb:
Phew, good question. I am much more familiar with heat pumps than with fireplaces. I’m not a big fan of fireplaces either. Today, we were also annoyed by the neighbors who filled the whole area with smoke...
Basically, I believe the connection was better before than it is now.
But the real question, as Mycraft already mentioned, is how the underfloor heating is connected.
And above all, were all the room thermostats set to 1 there as well?
You need to understand that once the temperature on those controllers is exceeded, they completely shut off the flow.
So this is not a regulation but rather an on/off function.
How is the heat from the fireplace supposed to be distributed to other rooms then?
The energy performance certificate has been mandatory since 2002, hasn’t it?!Yes, we already had it set like that at the time. Back then, the explanation was that the underfloor heating would absorb all the heat, so nothing would reach the buffer tank. But since it was unbearably hot here, we insisted on the renovation. And look, it works now. Here in the living room, the temperature is bearable, and the energy reaches the buffer tank.What exactly is the energy performance certificate supposed to be mandatory for?
R
RotorMotor21 Oct 2023 14:07Jessica388 schrieb:
Yes, we had it set up like that before, too. At that time, they also said the underfloor heating would consume all the heat, so nothing would reach the buffer tank. But since it got unbearably hot here, we insisted on the conversion. And look, it works now. It’s comfortable here in the living room, and energy reaches the buffer tank. Just because it flows through other pipes in the same storage tank, does that mean it should reach the buffer with one setup but not the other?
That doesn’t seem physically logical at first.
It’s possible it takes a bit longer, but if it didn’t work at all with the first setup, there must have been another reason.
Maybe a valve wasn’t open or something like that.
Jessica388 schrieb:
What is the energy certificate mandatory for? For residential buildings.
J
Jessica38821 Oct 2023 14:24RotorMotor schrieb:
Just because the water flows through other pipes in the same storage tank, it’s supposed to reach the destination in one setup but not in the other?
That doesn’t seem physically logical at first glance.
It might take a bit longer, but the fact that it didn’t work at all in one case must be due to something else.
Maybe the valve wasn’t open or something like that.
For residential buildings. I understood it as the old setup circulates in a closed loop, while the new setup connects directly to the main water volume.
No idea. We definitely don’t have anything like that and haven’t needed it so far.
RotorMotor schrieb:
Just because it flows through other pipes in the same storage tank, should it reach in one setup but not in the other?
That doesn’t really make sense from a physical point of view. Previously, the wood stove was connected so that it only heated the lower part of the storage tank, and stratification may have occurred. Now it is connected so that the entire storage tank is flowed through, which allows more heat to be transferred to the contents.
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