ᐅ What type of storage or domestic hot water heating is suitable with district heating?
Created on: 15 Jul 2023 08:18
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Good morning everyone,
I am still busy with my new build. It’s not easy these days with rising interest rates and all the political energy issues. However, it’s getting more concrete now, and I need to plan the utility room. Unfortunately, I have to build without a basement, so space is very limited. The district heating connection is already fixed.
The connected load will be around 8-10 kW. There will be underfloor heating everywhere. A household of 4 people. Only a small photovoltaic system (4.5 kW).
We are building in the town center in a commercial area, so our living, dining, and kitchen area will be on the top floor. There will only be a small kitchen unit there that requires hot water, so I want to avoid running a hot water pipe and instead use an electric tankless water heater under the sink.
I also need to supply two bathrooms. One on the ground floor, diagonally opposite the utility room, and the main bathroom directly above the utility room.
Which hot water system would you recommend that is modern and space-saving?
My options, based on what I have researched so far (I’m no expert):
Option 1: Instantaneous water heater station at the utility connection station:
My preferred option would be a fresh water transfer station with an integrated heating circuit and an integrated instantaneous water heater (tankless). No storage tank. These stations are quite compact (about 120x75x40 cm (47x30x16 inches), wall-mounted).
Unfortunately, this option was discouraged because it is apparently only suitable for larger connected loads. For fresh water, about 30 kW would have to be available briefly, which would result in high demand charges and strain the system (controllers, valves, water hammer, etc.), since the normal operation (without hot water demand) requires much less power, and then suddenly 30 kW for hot water. Unfortunately, I would have found this option hygienic and very space-saving!
Option 2: Hot water storage tank:
The simplest and still quite space-saving option might be to use a floor-standing storage tank (160 liters (42 gallons)) combined with a simple fresh water transfer station with an integrated heating circuit and drinking water heating that heats the boiler. According to my sketch, I could probably fit this in. The question is whether this is still state-of-the-art (hygienically and technically) and if a 160-liter (42-gallon) boiler is sufficient (not much bathing)?
Option 3.1: Buffer tank with instantaneous water heater at the transfer station:
I’m not sure if I have the space for this, but this option would use a 500-liter (132 gallons) buffer tank and a tankless water heater at the transfer station. Since I have limited space and feel this would result in relatively high heat losses, I’m not very convinced by this option.
Option 3.2: Buffer tank with instantaneous water heater at the buffer tank:
To me, this is basically the same as option 3.1.
What do you think? I’m not a professional and don’t know if I’ve understood everything correctly or missed anything, or if I have all relevant options in mind.
Of course, I will hire specialists for all services, but I want to start with a complete concept so I can fit everything in properly in the end.
For option 2, I created the utility room layout in PowerPoint.
Many thanks and best regards
I am still busy with my new build. It’s not easy these days with rising interest rates and all the political energy issues. However, it’s getting more concrete now, and I need to plan the utility room. Unfortunately, I have to build without a basement, so space is very limited. The district heating connection is already fixed.
The connected load will be around 8-10 kW. There will be underfloor heating everywhere. A household of 4 people. Only a small photovoltaic system (4.5 kW).
We are building in the town center in a commercial area, so our living, dining, and kitchen area will be on the top floor. There will only be a small kitchen unit there that requires hot water, so I want to avoid running a hot water pipe and instead use an electric tankless water heater under the sink.
I also need to supply two bathrooms. One on the ground floor, diagonally opposite the utility room, and the main bathroom directly above the utility room.
Which hot water system would you recommend that is modern and space-saving?
My options, based on what I have researched so far (I’m no expert):
Option 1: Instantaneous water heater station at the utility connection station:
My preferred option would be a fresh water transfer station with an integrated heating circuit and an integrated instantaneous water heater (tankless). No storage tank. These stations are quite compact (about 120x75x40 cm (47x30x16 inches), wall-mounted).
Unfortunately, this option was discouraged because it is apparently only suitable for larger connected loads. For fresh water, about 30 kW would have to be available briefly, which would result in high demand charges and strain the system (controllers, valves, water hammer, etc.), since the normal operation (without hot water demand) requires much less power, and then suddenly 30 kW for hot water. Unfortunately, I would have found this option hygienic and very space-saving!
Option 2: Hot water storage tank:
The simplest and still quite space-saving option might be to use a floor-standing storage tank (160 liters (42 gallons)) combined with a simple fresh water transfer station with an integrated heating circuit and drinking water heating that heats the boiler. According to my sketch, I could probably fit this in. The question is whether this is still state-of-the-art (hygienically and technically) and if a 160-liter (42-gallon) boiler is sufficient (not much bathing)?
Option 3.1: Buffer tank with instantaneous water heater at the transfer station:
I’m not sure if I have the space for this, but this option would use a 500-liter (132 gallons) buffer tank and a tankless water heater at the transfer station. Since I have limited space and feel this would result in relatively high heat losses, I’m not very convinced by this option.
Option 3.2: Buffer tank with instantaneous water heater at the buffer tank:
To me, this is basically the same as option 3.1.
What do you think? I’m not a professional and don’t know if I’ve understood everything correctly or missed anything, or if I have all relevant options in mind.
Of course, I will hire specialists for all services, but I want to start with a complete concept so I can fit everything in properly in the end.
For option 2, I created the utility room layout in PowerPoint.
Many thanks and best regards
WilderSueden schrieb:
I would install a hot water storage tank. However, 160 liters (42 gallons) runs out quickly after using the bathtub. You’d need to check how long it takes for the water to heat up again.We thought the same, but that’s not entirely true and it depends on the water temperature in the tank.
Do you bathe at 55°C (131°F)? Probably not.
We have a 120-liter (32 gallons) tank. It only becomes tight when the children have taken a bath (and keep the water running continuously), and then two people want to shower afterwards. One bath plus one shower immediately after or at the same time is not an issue. Even 3 to 4 showers in a row work fine.
Hmm, sounds like an Inuit family.
I have 190 liters (50 gallons) of water at 49°C (120°F), which should contain even more heat energy. If either I or the little one has taken a bath, my wife cannot shower right afterward. I might be able to shower after a bath (I shower cooler than the two of them), but without using a hair treatment.
I have 190 liters (50 gallons) of water at 49°C (120°F), which should contain even more heat energy. If either I or the little one has taken a bath, my wife cannot shower right afterward. I might be able to shower after a bath (I shower cooler than the two of them), but without using a hair treatment.
W
WilderSueden18 Jul 2023 13:15The problem is not just the total amount of hot water, but that cold water continuously flows back into the storage tank.
Cold water is about 15°C (59°F). If you fill the bathtub with 40°C (104°F) water, you need roughly two-thirds hot water at 55°C (131°F). Then it becomes a calculation of how large your storage tank must be to still have more than lukewarm water afterwards.
Cold water is about 15°C (59°F). If you fill the bathtub with 40°C (104°F) water, you need roughly two-thirds hot water at 55°C (131°F). Then it becomes a calculation of how large your storage tank must be to still have more than lukewarm water afterwards.
Although it doesn’t completely mix either. If the tank isn’t constructed in a completely poor way, fresh water enters at the bottom. So the top should still be relatively warm. But yes, the more water you have already used, the colder the remaining water becomes.
That said, I would say 160 liters (42 gallons) is a bit too small for four people. On the other hand, 500 liters (132 gallons) seems like a lot.
That said, I would say 160 liters (42 gallons) is a bit too small for four people. On the other hand, 500 liters (132 gallons) seems like a lot.
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