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
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neo-sciliar27 Aug 2020 13:45Bookstar schrieb:
In this project, everyone loses. Forget about the fireplace with water heating – financially, it’s a bottomless pit. You can’t burn your money more inefficiently, even if you get wood for free.Well, I just received the electricity bill for the last heating season. Almost exactly €300 (about $320) ... and we kept it comfortably warm in 22m² (240 ft²) of heated space, no KFW or similar subsidies.My questions are more about air-to-water heat pumps since we are building a new house. ... What's the difference between monoblock and split systems?
neo-sciliar schrieb:
What exactly is the difference between a monoblock and a split air-to-water heat pump? Does the monoblock have no outdoor unit? How is that supposed to work? With a monoblock, as the name suggests, you have only one unit, which is usually installed outside. With a split system, as the name implies, it is divided into a compressor unit inside and a heat exchanger unit outside.
D
Daniel-Sp27 Aug 2020 13:59A monoblock usually refers to a heat pump installed completely outdoors. A split heat pump consists of an outdoor unit and an indoor unit.
N
neo-sciliar27 Aug 2020 14:00Lumpi_LE schrieb:
With a monoblock, as the name suggests, you have just one unit, which is usually installed outdoors. With a split system, as the name also implies, the compressor is inside while the heat exchanger is outside.So, just as I suspected... a monoblock has the compressor located outside? Isn't that much more practical than a split system? But what about the hot water storage tank? It hardly would be installed outdoors... Do you then have the tank and the controls indoors? I'm still not quite sure how that works...N
nordanney27 Aug 2020 14:04neo-sciliar schrieb:
Difference between Monoblock and SplitThe monoblock unit has the refrigeration circuit installed inside the device. This makes it particularly interesting for DIY enthusiasts (no need for a refrigeration technician to connect the indoor and outdoor units). There is only one outdoor unit.The Panasonic units are especially well known – you can look them up. The new 5 kW (17,000 BTU/h) system has a COP of 4.9 (including domestic hot water) here in the Lower Rhine region.
neo-sciliar schrieb:
Is the storage tank inside, and the control system?The storage tank is located indoors. Control is via wired remote control or online.P.S. Monoblocks offer an excellent price/performance ratio. The Panasonic alone costs about €2,900 with 5 kW (17,000 BTU/h). With all accessories, you get the materials for around €4,000 plus underfloor heating. Most installers are not thrilled about that.
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