This is currently what my heating engineer is suggesting in combination with the existing pellet heating system, but I somehow can’t make sense of the fresh water station.
Originally, domestic hot water was produced using a separate hot water storage tank combined with an air-source heat pump for warm water exhaust, together with the photovoltaic system.
For a single-person household, all of this seems quite excessive to me.
With the fresh water station, I imagine that I would constantly need to keep the 500 liters (130 gallons) in the buffer tank at 45-55°C (113-131°F) to ensure that 30 liters (8 gallons) of hot water can be drawn on demand through the fresh water station. Even if electricity from the photovoltaic system is fed into the buffer tank via an electric heating element, there are still 500 liters (130 gallons) that need to be kept warm, right?
On the other hand, if I consider an 80-120 liter (21-32 gallons) hot water storage tank heated from the grid and/or photovoltaic system, only 80-120 liters (21-32 gallons) need to be heated.
Or am I misunderstanding the energy consumption of the fresh water station, and is my assumption incorrect because water is only drawn as needed?
Originally, domestic hot water was produced using a separate hot water storage tank combined with an air-source heat pump for warm water exhaust, together with the photovoltaic system.
For a single-person household, all of this seems quite excessive to me.
With the fresh water station, I imagine that I would constantly need to keep the 500 liters (130 gallons) in the buffer tank at 45-55°C (113-131°F) to ensure that 30 liters (8 gallons) of hot water can be drawn on demand through the fresh water station. Even if electricity from the photovoltaic system is fed into the buffer tank via an electric heating element, there are still 500 liters (130 gallons) that need to be kept warm, right?
On the other hand, if I consider an 80-120 liter (21-32 gallons) hot water storage tank heated from the grid and/or photovoltaic system, only 80-120 liters (21-32 gallons) need to be heated.
Or am I misunderstanding the energy consumption of the fresh water station, and is my assumption incorrect because water is only drawn as needed?
B
Benutzer2009 Apr 2022 11:42lesmue79 schrieb:
My heating engineer is currently suggesting this in combination with the existing pellet heating system. lesmue79 schrieb:
Or am I misjudging the energy consumption of the domestic hot water station? How much is this going to cost? Around €3,000–5,000 including installation? Have you considered how long you could run even the simplest tankless water heater for that amount (probably for the rest of your life)?
He should give you a clear explanation of why he wants to proceed this way.
Probably because I overwhelmed him a bit with my requests. I wanted to find a way to use the photovoltaic surplus and have a backup with the electric heating element in case the pellet heating system fails.
That’s why I planned the fresh water station connected to the buffer tank and added a 3 kW heating element in the buffer. The ideal scenario would be that the pellet heating is off during the summer. The photovoltaic heating element would then heat the buffer tank using power from the solar panels, and the fresh water station could cover the domestic hot water demand from that. If the pellet boiler fails, the heating element could maintain the buffer temperature, either from the grid or via the photovoltaic system. But now I’m stuck on the fact that the 500-liter (130-gallon) buffer is constantly kept warm during summer just for hot water.
As I said, a purely electric boiler (a direct electric water heater is out due to the power supply) with 80–120 liters (20–30 gallons) capacity and a photovoltaic input connection would be sufficient. Such a unit probably costs less than €1000 installed, and only about 100 liters (25 gallons) of hot water are kept warm.
The fresh water station should cost around €3500, and with the assumed €2500 price difference, I could buy quite a bit of electricity if the photovoltaic system doesn’t produce enough.
That’s why I planned the fresh water station connected to the buffer tank and added a 3 kW heating element in the buffer. The ideal scenario would be that the pellet heating is off during the summer. The photovoltaic heating element would then heat the buffer tank using power from the solar panels, and the fresh water station could cover the domestic hot water demand from that. If the pellet boiler fails, the heating element could maintain the buffer temperature, either from the grid or via the photovoltaic system. But now I’m stuck on the fact that the 500-liter (130-gallon) buffer is constantly kept warm during summer just for hot water.
As I said, a purely electric boiler (a direct electric water heater is out due to the power supply) with 80–120 liters (20–30 gallons) capacity and a photovoltaic input connection would be sufficient. Such a unit probably costs less than €1000 installed, and only about 100 liters (25 gallons) of hot water are kept warm.
The fresh water station should cost around €3500, and with the assumed €2500 price difference, I could buy quite a bit of electricity if the photovoltaic system doesn’t produce enough.
D
Deliverer9 Apr 2022 16:21The suggestion probably comes from the fact that if you only use a hot water storage tank alone, it rarely empties completely, which can lead to legionella issues. The instant water heater doesn’t have this problem.
I don’t have a better idea than an instant water heater, though.
On the other hand, a pellet boiler can easily heat the storage tank to 70°C (158°F), so it’s less of an issue if the water draw-off is low. If you then switch to a heat pump, you’ll need to reconsider.
I don’t have a better idea than an instant water heater, though.
On the other hand, a pellet boiler can easily heat the storage tank to 70°C (158°F), so it’s less of an issue if the water draw-off is low. If you then switch to a heat pump, you’ll need to reconsider.
Secretly, I was hoping there is a fully electric hot water storage tank around 80 liters (21 gallons). This way, I could set the heating schedule with a timer to heat mostly around midday, so the heating would usually occur when power is available from the roof or the photovoltaic system.
D
Deliverer9 Apr 2022 17:06I would almost say that such devices exist. However, these units are often quite powerful and not adjustable in terms of output. How much photovoltaic capacity do you have on your roof?
What about a domestic hot water heat pump? These are available in compact units combined with different storage sizes. This way, you are completely independent from the pellet stove and can optimally use the photovoltaic output spread throughout the day. And that with a minimum coefficient of performance of 3.
The probably most practical option would be: remove the pellet stove, install an air-to-water heat pump without a buffer tank but with a small 100-liter (26-gallon) hot water storage tank. Hot water would then almost always come from the roof (schedule it around midday), and you can also contribute a significant portion of the heating demand with solar power. This can easily reduce CO2 emissions by a factor of 3.
What about a domestic hot water heat pump? These are available in compact units combined with different storage sizes. This way, you are completely independent from the pellet stove and can optimally use the photovoltaic output spread throughout the day. And that with a minimum coefficient of performance of 3.
The probably most practical option would be: remove the pellet stove, install an air-to-water heat pump without a buffer tank but with a small 100-liter (26-gallon) hot water storage tank. Hot water would then almost always come from the roof (schedule it around midday), and you can also contribute a significant portion of the heating demand with solar power. This can easily reduce CO2 emissions by a factor of 3.
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