ᐅ Combine an air-to-water heat pump with a wood-burning stove connected to the central heating system
Created on: 29 Mar 2020 14:13
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GSGaucho
Hello everyone,
We are currently planning a single-family home built with solid construction to KFW55 standard.
Two full stories, partially basement, without basement about 230m² (2,475 sq ft) of living space for 5 people.
The location is southern Germany at 550m (1,804 ft) above sea level. The shell construction planning is fixed, and the shell and gable roof have already been contracted. Construction start is week 22/2020.
I have also already contracted a 23kWp photovoltaic system on the south/west roof of the house and the south/east roof of the garage.
Due to economic reasons, a battery storage system is currently not an option.
The heating load according to calculation is about 5.5 kW at -15°C (5°F) ambient temperature.
Now it’s time to plan the heating system:
Current status is:
Now I have the first offer for a Stiebel Eltron LWZ 8 cs Premium.
Am I correct to assume that under the above parameters the LWZ 5 cs would also be sufficient?
How can I best integrate the Hoxter stove into the heating system?
As a layperson, I currently see two options:
Option 1
An 800-liter (210-gallon) buffer tank only for heating operation, without domestic hot water.
Domestic hot water is generated by the air-to-water heat pump during daylight; the heat pump runs mainly during the day and stores heat in the screed. From 4 p.m. onward, the Hoxter stove is fired.
The heating circuit would then have to switch to the buffer tank when a certain temperature X is reached in the stove circuit or the heat pump buffer.
Option 2
The air-to-water heat pump always charges the buffer tank with a maximum flow temperature of about 40°C (104°F). If this temperature is exceeded by the stove operation, the heat pump switches off. Also, the heat pump would be programmed to operate only during daytime.
I understand that the combination of air-to-water heat pump with a buffer tank is suboptimal. But a stove without hydronic integration also makes no sense, as it would quickly overheat.
My current bidder is almost unreachable for technical evaluation at the moment, fully booked, so I have no real information about integrating the stove yet.
What do you suggest?
Which other air-to-water heat pump manufacturers would you consider for this configuration?
Thank you very much,
GSGaucho
We are currently planning a single-family home built with solid construction to KFW55 standard.
Two full stories, partially basement, without basement about 230m² (2,475 sq ft) of living space for 5 people.
The location is southern Germany at 550m (1,804 ft) above sea level. The shell construction planning is fixed, and the shell and gable roof have already been contracted. Construction start is week 22/2020.
I have also already contracted a 23kWp photovoltaic system on the south/west roof of the house and the south/east roof of the garage.
Due to economic reasons, a battery storage system is currently not an option.
The heating load according to calculation is about 5.5 kW at -15°C (5°F) ambient temperature.
Now it’s time to plan the heating system:
Current status is:
- Underfloor heating in all rooms except for the pantry and storage/technical room in the basement.
- Central ventilation system combined with an air-to-water heat pump. Air-to-water heat pump installed indoors in the basement.
- A hydronic wood-burning stove from Hoxter with firing from a separate room, i.e., no wood/dirt in the living room. I still have 30rm (cords) of beech wood stored free of charge.
- Due to the high capacity of the photovoltaic system and the stove, I see no sense in a trench collector.
- An 800-liter (210-gallon) buffer tank can be placed almost directly under the Hoxter stove in the basement. The distance to the air-to-water heat pump is about 2.5m (8 feet).
Now I have the first offer for a Stiebel Eltron LWZ 8 cs Premium.
Am I correct to assume that under the above parameters the LWZ 5 cs would also be sufficient?
How can I best integrate the Hoxter stove into the heating system?
As a layperson, I currently see two options:
Option 1
An 800-liter (210-gallon) buffer tank only for heating operation, without domestic hot water.
Domestic hot water is generated by the air-to-water heat pump during daylight; the heat pump runs mainly during the day and stores heat in the screed. From 4 p.m. onward, the Hoxter stove is fired.
The heating circuit would then have to switch to the buffer tank when a certain temperature X is reached in the stove circuit or the heat pump buffer.
Option 2
The air-to-water heat pump always charges the buffer tank with a maximum flow temperature of about 40°C (104°F). If this temperature is exceeded by the stove operation, the heat pump switches off. Also, the heat pump would be programmed to operate only during daytime.
I understand that the combination of air-to-water heat pump with a buffer tank is suboptimal. But a stove without hydronic integration also makes no sense, as it would quickly overheat.
My current bidder is almost unreachable for technical evaluation at the moment, fully booked, so I have no real information about integrating the stove yet.
What do you suggest?
Which other air-to-water heat pump manufacturers would you consider for this configuration?
Thank you very much,
GSGaucho
Bookstar schrieb:
Unfortunately, decibel levels say very little about noise disturbance. It is more about the type of sounds, especially low-frequency tones. ...which are specifically filtered out in dB(A) measurements (dB(C) values would be more meaningful). The sound pressure levels of low frequencies are rated lower here because they are less audible to humans (which is why the A-weighting exists), but they can still sometimes be felt or transmitted through structure-borne sound.
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neo-sciliar27 Aug 2020 15:54The question is: does a monoblock unit bother the neighbors (and myself), or is it generally not noticeable?
N
nordanney27 Aug 2020 16:09Under normal circumstances, with proper placement—not directly under the bedroom window or similar—the devices do not cause any disturbance.
If the heat pump is designed for integration with solar thermal systems, coupling a low-temperature (LT) system with a high-temperature (HT) system works quite well.
The heat pump detects via the upper temperature sensor in the buffer tank that it is charged and accordingly cycles the intermediate circulation pump. An internal heat exchanger integrated within the heat pump warms the heat pump circuit so that a flow temperature (FT) of 30°C (86°F) is reached in the heating circuit, or, during domestic hot water operation, the set temperature is achieved. The compressor does not cycle and remains off during this process, only restarting when the buffer temperature drops below approximately 30°C (86°F).
If self-installed, the additional costs compared to a chimney insert without water are well below 3,000.
Whether this is worth it or not is of relatively little concern to me. The alternative would simply be to forgo a wood stove entirely.
The heat pump detects via the upper temperature sensor in the buffer tank that it is charged and accordingly cycles the intermediate circulation pump. An internal heat exchanger integrated within the heat pump warms the heat pump circuit so that a flow temperature (FT) of 30°C (86°F) is reached in the heating circuit, or, during domestic hot water operation, the set temperature is achieved. The compressor does not cycle and remains off during this process, only restarting when the buffer temperature drops below approximately 30°C (86°F).
If self-installed, the additional costs compared to a chimney insert without water are well below 3,000.
Whether this is worth it or not is of relatively little concern to me. The alternative would simply be to forgo a wood stove entirely.
D
Daniel-Sp3 Sep 2020 20:48Is the buffer tank completely disconnected from the heating circuit when temperatures drop below 30°C (86°F)?
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