ᐅ Which Heating System for Maintaining a Room Temperature of 23 °C
Created on: 14 Sep 2020 13:46
F
Fetzerino
Hello community,
For the past few days, I have been researching current heating technologies and feel that it raises more questions than answers, which is why I am now turning to you with my questions in the hope that experienced users of this system can provide some answers.
My wife and I would like to build a KFW40+ house with about 130 sqm (1400 sq ft). The house will have an unobstructed southern exposure, meaning plenty of sun in both summer and winter. A photovoltaic system will be installed on the roof. At the moment, we are leaning towards a prefabricated house, but we are still in the decision-making phase.
We both currently live in an apartment with underfloor heating and a gas boiler, and we find the warmth emitted by the underfloor heating very comfortable. I have set the central room temperature to 23°C (73°F) on the gas boiler because we both like it quite warm, although this can be adjusted downward locally with thermostats.
With a prefabricated house, the Proxon air-to-air heat pump is usually offered as the solution on the market. However, further research reveals advantages and disadvantages of this technology, as with any topic. I have read so far that many heat their rooms to 20–21°C (68–70°F) using the air-to-air heat pump. However, I have not yet found out whether it is possible to reach 23°C (73°F) with an air-to-air heat pump without the use of auxiliary heating panels. The question is also what power consumption these auxiliary panels have. The sales representative of the prefab house provider mentioned that with these auxiliary heating panels, the room can be warmed quite quickly (within 5 minutes). Ultimately, the whole setup works like a hairdryer. But if I hold a 2 kW hairdryer in a room, I don’t notice a significant difference after 5 minutes.
Question: Can I achieve a room temperature of 23°C (73°F) without auxiliary heating panels, even in larger rooms? What is the power consumption of such an auxiliary heating panel? Does anyone have additional consumption data for this heating solution? How does it perform on cold winter days? Ultimately, it is about the indoor climate, and 23°C (73°F) is not always the same 23°C (73°F), which I understand.
As an alternative, it seems that an air-to-water heat pump is also an option. In terms of efficiency, this is said to be similar to the air-to-air heat pump but more expensive to install because pipes must be laid. However, since the flow temperature is lower, it should be more economical to operate. Is that correct? With this type of heating, there should be no problem achieving 23°C (73°F) even in larger rooms, right? Does anyone also have consumption data here? Of course, it depends on individual behavior, which I understand, but figures can help build a sense for it.
Cooling in summer is not possible with this heating system but should be possible as an add-on with an air-to-air heat pump. Does a KFW40+ house get very warm in summer?
Thank you very much for your help and information.
For the past few days, I have been researching current heating technologies and feel that it raises more questions than answers, which is why I am now turning to you with my questions in the hope that experienced users of this system can provide some answers.
My wife and I would like to build a KFW40+ house with about 130 sqm (1400 sq ft). The house will have an unobstructed southern exposure, meaning plenty of sun in both summer and winter. A photovoltaic system will be installed on the roof. At the moment, we are leaning towards a prefabricated house, but we are still in the decision-making phase.
We both currently live in an apartment with underfloor heating and a gas boiler, and we find the warmth emitted by the underfloor heating very comfortable. I have set the central room temperature to 23°C (73°F) on the gas boiler because we both like it quite warm, although this can be adjusted downward locally with thermostats.
With a prefabricated house, the Proxon air-to-air heat pump is usually offered as the solution on the market. However, further research reveals advantages and disadvantages of this technology, as with any topic. I have read so far that many heat their rooms to 20–21°C (68–70°F) using the air-to-air heat pump. However, I have not yet found out whether it is possible to reach 23°C (73°F) with an air-to-air heat pump without the use of auxiliary heating panels. The question is also what power consumption these auxiliary panels have. The sales representative of the prefab house provider mentioned that with these auxiliary heating panels, the room can be warmed quite quickly (within 5 minutes). Ultimately, the whole setup works like a hairdryer. But if I hold a 2 kW hairdryer in a room, I don’t notice a significant difference after 5 minutes.
Question: Can I achieve a room temperature of 23°C (73°F) without auxiliary heating panels, even in larger rooms? What is the power consumption of such an auxiliary heating panel? Does anyone have additional consumption data for this heating solution? How does it perform on cold winter days? Ultimately, it is about the indoor climate, and 23°C (73°F) is not always the same 23°C (73°F), which I understand.
As an alternative, it seems that an air-to-water heat pump is also an option. In terms of efficiency, this is said to be similar to the air-to-air heat pump but more expensive to install because pipes must be laid. However, since the flow temperature is lower, it should be more economical to operate. Is that correct? With this type of heating, there should be no problem achieving 23°C (73°F) even in larger rooms, right? Does anyone also have consumption data here? Of course, it depends on individual behavior, which I understand, but figures can help build a sense for it.
Cooling in summer is not possible with this heating system but should be possible as an add-on with an air-to-air heat pump. Does a KFW40+ house get very warm in summer?
Thank you very much for your help and information.
That’s fine and even positive if you use very little. But I have an issue with presenting that as normal. Your annual hot water costs would be about 30 euros in summer and maybe 100 euros in winter. That totals 130 euros. I have data ranging from a low of 240 euros to a very high 540 euros. So your value is completely outside the usual range.
According to statistics, one person needs about 40 liters (10.5 gallons) of hot water daily on average. For two people, that’s 80 liters (21 gallons). This doesn’t include heat losses, which depending on the heating system design can easily double the energy needed for heating. Without losses, that’s about 6 kWh of energy. With a COP of 4, it would be 1.25 kWh. That would already be the upper range for you. Achieving 0.8 kWh is only possible on vacation or with even lower consumption.
But okay, my coworker shuts off hot water for his entire family during summer. He’s quite a saver. In winter, they have 14°C (57°F) in the bedroom and wear scarves. Everything’s possible, but let’s just say that’s quite... special!
We are probably the opposite. We shower daily, cook a lot, and likely use several hundred liters of hot water daily. For us, 3 kWh for heating is already a very good value.
According to statistics, one person needs about 40 liters (10.5 gallons) of hot water daily on average. For two people, that’s 80 liters (21 gallons). This doesn’t include heat losses, which depending on the heating system design can easily double the energy needed for heating. Without losses, that’s about 6 kWh of energy. With a COP of 4, it would be 1.25 kWh. That would already be the upper range for you. Achieving 0.8 kWh is only possible on vacation or with even lower consumption.
But okay, my coworker shuts off hot water for his entire family during summer. He’s quite a saver. In winter, they have 14°C (57°F) in the bedroom and wear scarves. Everything’s possible, but let’s just say that’s quite... special!
We are probably the opposite. We shower daily, cook a lot, and likely use several hundred liters of hot water daily. For us, 3 kWh for heating is already a very good value.
Bookstar schrieb:
That’s quite interesting. Either you use very little hot water, or you’re breaking the physical limits. I don’t believe your heat pump produces more than 4 kWh of heat from 1 kWh of electricity if it’s an air-to-water heat pump. We need about 200 liters (53 gallons) of hot water daily for two people, and some of it cools down unused. That’s 12 kWh; at a COP of 4, that equals 3 kWh of electricity effectively. So you'd have to manage with 70 liters (18 gallons) of hot water, and the tank would have no losses.
Please explain that to me—there’s no way even one person could take a warm shower with that amount… Just to bring a counterexample here….
I found your consumption quite high, so I checked ours.
We moved in about 4 years ago, I think 3 or 4 weeks after the new meters were installed, which is why I could read the hot water consumption accurately.
Kitchen: 4.9 m³ (173 ft³)
Bathroom: 36.8 m³ (1300 ft³)
We moved in as a family of three: two adults and a baby. Now we are two adults and two children aged 3 and 5.
If I divide our total hot water consumption of 41.7 m³ (1472 ft³) by 4 years and 365 days, I get an average consumption of nearly 30 liters (8 gallons) per day.
I don’t want to present this as normal since we are quite economical. In summer, I often take cold showers. In winter, the hot water in the kitchen is frequently heated using our wood stove for washing up.
That’s why I don’t consider 70 liters (18 gallons) to be unrealistic.
This is just intended as a thought-provoking example to show that there are simply different figures. I realize that we are also far outside the norm.
Regards
Specki
D
Daniel-Sp15 Sep 2020 17:11Correct me if my calculation is wrong.
With a COP of 3.5, I get 3.5 kWh of heat. To heat 1 m³ of water by 1 degree, I need 1.16 kWh. Therefore, with 1 kWh of electrical energy, I can achieve approximately a 9° temperature increase in a 300-liter (79-gallon) storage tank. This matches our system. The target temperature is 48°C (118°F), and it is usually heated once, mostly around 12:00 noon. The storage temperature is then usually around 38–40°C (100–104°F).
In winter, we use more hot water.
With a COP of 3.5, I get 3.5 kWh of heat. To heat 1 m³ of water by 1 degree, I need 1.16 kWh. Therefore, with 1 kWh of electrical energy, I can achieve approximately a 9° temperature increase in a 300-liter (79-gallon) storage tank. This matches our system. The target temperature is 48°C (118°F), and it is usually heated once, mostly around 12:00 noon. The storage temperature is then usually around 38–40°C (100–104°F).
In winter, we use more hot water.
So I see it, you are drawing water and need to heat new water from about 15°C (59°F) cold tap water to 48°C (118°F). Additionally, the remaining water in the buffer tank cools down from 48°C (118°F) to 40°C (104°F) during standby time and then needs to be reheated as well.
Therefore, in my view, your calculation is not correct.
Therefore, in my view, your calculation is not correct.
D
Daniel-Sp15 Sep 2020 20:46I originally thought that the withdrawal of hot water and the refilling with fresh water happened simultaneously. Hot water is drawn from the top, while cold water flows in at the bottom. The temperature inside the tank varies at different points.
In any case, this is how it works for us. After heating, the tank temperature is 48°C (118°F). The next day, before reheating, it drops to 38-40°C (100-104°F) due to cooling and usage. Then it heats back up to 48°C (118°F) using 1 kWh. This cycle generally occurs once every 24 hours, with few exceptions.
In any case, this is how it works for us. After heating, the tank temperature is 48°C (118°F). The next day, before reheating, it drops to 38-40°C (100-104°F) due to cooling and usage. Then it heats back up to 48°C (118°F) using 1 kWh. This cycle generally occurs once every 24 hours, with few exceptions.
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