ᐅ New Construction, Wood-Burning Stove, Nominal Heat Output—What Now?
Created on: 8 Nov 2017 10:08
O
onyx.dop
Hello everyone,
We are currently planning a new build and would like to include a wood-burning stove (a heating insert built with firebrick) in the open living/dining/kitchen area. The goal is to slightly reduce the load on the air-to-water heat pump and create a cozy atmosphere.
My heat load calculation based on the U-value shows that for 64m² (living/dining/kitchen + hallway connected by two doors) we need a maximum heating capacity of about 2.3 kW. This includes all external walls (approximately U-value 0.19) and floor construction (0.16).
If I install a stove with a nominal heat output of 9 kW and an output range of 3.2 to 10.9 kW, won’t I overheat the space even at the minimum wood feed rate (3.2 kW)? According to the stove fitter, this is not a problem because the heat output can be controlled by adjusting the amount of wood.
The 2.3 kW figure also refers to the worst-case scenario of -16°C (3°F) outside and +23°C (73°F) inside, without any other heat sources. So, in reality, the required heating capacity will likely be much lower than 2.3 kW.
What is the best approach? Should I choose a stove insert with the lowest possible heat output range?
Best regards.
We are currently planning a new build and would like to include a wood-burning stove (a heating insert built with firebrick) in the open living/dining/kitchen area. The goal is to slightly reduce the load on the air-to-water heat pump and create a cozy atmosphere.
My heat load calculation based on the U-value shows that for 64m² (living/dining/kitchen + hallway connected by two doors) we need a maximum heating capacity of about 2.3 kW. This includes all external walls (approximately U-value 0.19) and floor construction (0.16).
If I install a stove with a nominal heat output of 9 kW and an output range of 3.2 to 10.9 kW, won’t I overheat the space even at the minimum wood feed rate (3.2 kW)? According to the stove fitter, this is not a problem because the heat output can be controlled by adjusting the amount of wood.
The 2.3 kW figure also refers to the worst-case scenario of -16°C (3°F) outside and +23°C (73°F) inside, without any other heat sources. So, in reality, the required heating capacity will likely be much lower than 2.3 kW.
What is the best approach? Should I choose a stove insert with the lowest possible heat output range?
Best regards.
Evolith schrieb:
Or did I misunderstand the technology? Setting the controller to 1 means the valve is closed. What you want—"heating not so powerfully"—is the self-regulating effect mentioned above, which the heating system achieves automatically without the unnecessary ERR.
Musketier schrieb:
Setting the controller to 1 means the valve is closed. What you want, "not to heat so powerfully," is the self-regulation effect mentioned above, which the heating system automatically provides without the silly ERR.Oh, no, for us setting it to 1 only lets a little flow through. We also have the 0 setting.
Evolith schrieb:
Oh, I see, no, for us a 1 means it only lets through a little bit.
We still have the 0.I don’t think so. The regulations only allow for open or closed. The number just indicates the temperature at which it opens or closes.
Room thermostats generally operate digitally. When the room temperature falls below the set value, the thermostat switches ON; when the temperature rises above the set value, it switches OFF (except for a preset or adjustable hysteresis). It is best to set all room thermostats to the maximum value and then adjust the heating control accordingly to achieve the desired temperature. When planning the design of underfloor heating, rooms with higher or lower heat demand can be taken into account. This is not done (only) with the room thermostat.
Regarding the "savings effect":
Basically, every house has a heat demand that depends on many factors. In many families, it happens that the woman prefers a few degrees warmer than the man or the rest of the household. The result is that "the heating needs to be turned up."
If I set my base heat demand—let’s say a room temperature of 21°C (70°F)—using the heating system and cover the "additional demand from the woman" with a wood stove, I naturally save on heating costs. Without the stove, this extra demand would have to be covered by the heating system (or a few blankets or a space heater *facepalm*). The actual amount of energy saved is debatable.
Of course, the heating system is designed for a certain temperature, and usually a later-installed wood stove is not considered in this calculation (unless it has a water jacket). Still, with a heat pump, for example, there are basically only two modes: pump ON or OFF. When ON, the buffer tank (if present) is heated; when OFF, it is not (keyword: cycling). If my total demand is slightly lower—say just by 1°C (1.8°F)—the heat pump cycles less because less heat is drawn from the buffer.
In the end, the wood stove will probably never pay for itself. It is more of a gimmick or luxury item, used more by some than others. Therefore, it is better not to consider it in heat planning. On the other hand, you can be glad later if you can slightly adjust the heating curve and save a few dollars or euros on heating costs each year.
Regarding the "savings effect":
Basically, every house has a heat demand that depends on many factors. In many families, it happens that the woman prefers a few degrees warmer than the man or the rest of the household. The result is that "the heating needs to be turned up."
If I set my base heat demand—let’s say a room temperature of 21°C (70°F)—using the heating system and cover the "additional demand from the woman" with a wood stove, I naturally save on heating costs. Without the stove, this extra demand would have to be covered by the heating system (or a few blankets or a space heater *facepalm*). The actual amount of energy saved is debatable.
Of course, the heating system is designed for a certain temperature, and usually a later-installed wood stove is not considered in this calculation (unless it has a water jacket). Still, with a heat pump, for example, there are basically only two modes: pump ON or OFF. When ON, the buffer tank (if present) is heated; when OFF, it is not (keyword: cycling). If my total demand is slightly lower—say just by 1°C (1.8°F)—the heat pump cycles less because less heat is drawn from the buffer.
In the end, the wood stove will probably never pay for itself. It is more of a gimmick or luxury item, used more by some than others. Therefore, it is better not to consider it in heat planning. On the other hand, you can be glad later if you can slightly adjust the heating curve and save a few dollars or euros on heating costs each year.
K
Knallkörper9 Nov 2017 11:34I would like to clarify the issue of overheating caused by the fireplace. We installed a very slow-responding stove with a 7 kW output. It takes about 3 hours for the cladding to warm up. Only then is the full heating capacity actually delivered to the room. After the fire goes out, the stove continues to radiate heat for several hours. On average, the room temperature is around 22 degrees Celsius (72°F) when lighting the fire, rising to a peak of 24 degrees Celsius (75°F) after a few hours. By the next evening, the temperature returns to 22 degrees Celsius (72°F).
In our old house, we had a stove without storage, also 7 kW. It gave off heat immediately after lighting, which would drive you off the couch. But once the fire burned down, it quickly became cold again (poorly insulated wooden house).
Including the chimney, such a stove costs at least 9,000 euros, more likely around 10,000 euros. It will never really pay off financially.
In our old house, we had a stove without storage, also 7 kW. It gave off heat immediately after lighting, which would drive you off the couch. But once the fire burned down, it quickly became cold again (poorly insulated wooden house).
Including the chimney, such a stove costs at least 9,000 euros, more likely around 10,000 euros. It will never really pay off financially.
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