Hello everyone,
there is a topic that’s been on my mind. I only have some theoretical knowledge and don’t fully understand it yet, so I wanted to ask you. Maybe I’m already on the right track, but I’m not completely sure.
If I build a KfW 40 house and install a heat pump, I usually have underfloor heating.
The heat pump will probably heat the heating circuit based on demand. Do I also have a buffer tank here, or is it basically just the water in the heating circuit?
How does hot water generation work with a heat pump?
Is it common to have, let’s say, a 120-liter (32-gallon) hot water storage tank that is heated? Is this usually included with the system, or do I need an external buffer tank?
Or is it done without a large intermediate buffer, with the heat generated “online”? I suspect this might not work well since the heat pump is not usually sized that large.
Can the heat pump handle this in winter at all, or is it necessary to have an electric heating element switched on? The hot water should be heated to about 45°C (113°F), and in winter we can have temperatures down to around -15°C (5°F), so that would be a temperature difference of 60°C (108°F). I imagine that puts a lot of strain on the system.
Maybe you can help explain this a bit. Despite having quite a bit of knowledge about house building and heating, this part isn’t entirely clear to me yet. But maybe I’m already more or less right.
Thanks for your experience and knowledge.
Best regards,
Specki
there is a topic that’s been on my mind. I only have some theoretical knowledge and don’t fully understand it yet, so I wanted to ask you. Maybe I’m already on the right track, but I’m not completely sure.
If I build a KfW 40 house and install a heat pump, I usually have underfloor heating.
The heat pump will probably heat the heating circuit based on demand. Do I also have a buffer tank here, or is it basically just the water in the heating circuit?
How does hot water generation work with a heat pump?
Is it common to have, let’s say, a 120-liter (32-gallon) hot water storage tank that is heated? Is this usually included with the system, or do I need an external buffer tank?
Or is it done without a large intermediate buffer, with the heat generated “online”? I suspect this might not work well since the heat pump is not usually sized that large.
Can the heat pump handle this in winter at all, or is it necessary to have an electric heating element switched on? The hot water should be heated to about 45°C (113°F), and in winter we can have temperatures down to around -15°C (5°F), so that would be a temperature difference of 60°C (108°F). I imagine that puts a lot of strain on the system.
Maybe you can help explain this a bit. Despite having quite a bit of knowledge about house building and heating, this part isn’t entirely clear to me yet. But maybe I’m already more or less right.
Thanks for your experience and knowledge.
Best regards,
Specki
boxandroof schrieb:
If the bathtub has standard dimensions, for hygiene reasons choose the smallest heat pump-compatible storage tank possible with a large heat exchanger of 2-3 m² (21.5-32 ft²). 200 liters (53 gallons) are more than enough for your needs, so the water does not stay stored for too long. Smaller heat pump storage tanks are not available. I would try to avoid circulation. Alternatively, a domestic hot water station can be used, but in my opinion it is not necessary. However, research Legionella and make your own decision.
The original poster must be aware that circulation consumes a lot of energy and should, if necessary, only be activated during the main usage times. Depending on the distance between the bathroom and the heating room, I would consider including one for comfort reasons.
michert schrieb:
The original poster must understand that a circulation system uses quite a bit of energy and should ideally only be activated during the main usage times. Depending on the distance between the bathroom and the boiler room, I would consider installing one for comfort reasons. No, circulation will definitely not be used.
Specki schrieb:
200 liters (53 gallons) should be more than enough, I would even go as low as 150 liters (40 gallons). I believe we currently have only 210 liters (55 gallons) installed in our two-family house with 4 adults and 4 children. It’s important not to confuse the fact that 210 liters (55 gallons) of hot water storage aren’t all the same. Do you have gas and maybe solar thermal in your two-family house? Then the water is often heated up to 90°C (194°F). With a heat pump, it rarely reaches more than 50°C (122°F). That means your 210 liters (55 gallons) with a heat pump could be equivalent to about 400 liters (106 gallons) with gas or solar thermal.
150 liters (40 gallons) is far too little; that’s enough for a single household or for systems with supply temperatures suitable for showering at work, etc.
B
boxandroof28 Nov 2019 09:10Gas is a different matter. Check your current daily consumption. If you regularly have long showers or use a rain shower, or if people shower and bathe one after another, you might need to consider more than 300 liters (approximately 80 gallons). With a heat pump, the storage tank starts off cold when it is cold. The downside of a large tank is that the water can stand for a long time at temperatures that are not ideal for hygiene when demand is low.
A smaller tank can be managed by higher temperatures and more frequent heating cycles, which uses more electricity with high water demand than a large tank, but for hygiene reasons, I personally prefer this option.
A smaller tank can be managed by higher temperatures and more frequent heating cycles, which uses more electricity with high water demand than a large tank, but for hygiene reasons, I personally prefer this option.
The integrated storage tanks have a capacity of 160-210 liters (42-55 gallons), depending on the model and manufacturer.
Refilling takes a while, so for the few occasions when you have visitors, it might be tight.
It’s hardly comparable to a gas heating system. A typical gas burner usually provides over 10, 20 kW. When it kicks in, it produces hot water on demand.
Pay attention to the terminology. A buffer tank refers to a buffer between the heating system and underfloor heating. When talking about domestic hot water, the term used is hot water storage tank.
Refilling takes a while, so for the few occasions when you have visitors, it might be tight.
It’s hardly comparable to a gas heating system. A typical gas burner usually provides over 10, 20 kW. When it kicks in, it produces hot water on demand.
Pay attention to the terminology. A buffer tank refers to a buffer between the heating system and underfloor heating. When talking about domestic hot water, the term used is hot water storage tank.
We are currently running the hot water tank at 50°C (122°F). Yes, it’s gas-powered. That’s why we only have 200 liters (53 gallons) for twice the number of people.
That’s why I think 150 to 200 liters (40 to 53 gallons) with a heat pump would be sufficient for us.
I’ve already shared some information about our showering and bathing habits earlier. We simply don’t need much hot water.
@guckuck2
Thanks for the tip, I will take it into account.
And your other comments align with what I have written.
That’s why I think 150 to 200 liters (40 to 53 gallons) with a heat pump would be sufficient for us.
I’ve already shared some information about our showering and bathing habits earlier. We simply don’t need much hot water.
@guckuck2
Thanks for the tip, I will take it into account.
And your other comments align with what I have written.
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