ᐅ What size hot water storage tank is needed with a heat pump?
Created on: 20 Feb 2024 12:09
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BackSteinGotik
I am currently wondering what size is more suitable for a single-family house with 4 people (without a bathtub): 200 liters or, to be on the safe side, 300 liters?
Leaving guests aside — the typical scenario would be all 4 people showering in quick succession in the morning. Another case would be everyone taking a quick shower in the evening after swimming outdoors in summer.
With a water storage temperature of 50-55 degrees Celsius (122-131°F) and showering at 35-38 degrees Celsius (95-100°F), cold water is still mixed in. Calculated, at 7 minutes of showering per person and 10 liters per minute, the demand would be 280 liters (74 gallons) of mixed water. If you shower at 40 degrees Celsius (104°F) and only have 50 degrees Celsius (122°F) in the tank, it gets tight — then 210 liters (55 gallons) would be needed.
Still, the difference to 300 liters (79 gallons) seems quite large to me. How does this look in practice?
Leaving guests aside — the typical scenario would be all 4 people showering in quick succession in the morning. Another case would be everyone taking a quick shower in the evening after swimming outdoors in summer.
With a water storage temperature of 50-55 degrees Celsius (122-131°F) and showering at 35-38 degrees Celsius (95-100°F), cold water is still mixed in. Calculated, at 7 minutes of showering per person and 10 liters per minute, the demand would be 280 liters (74 gallons) of mixed water. If you shower at 40 degrees Celsius (104°F) and only have 50 degrees Celsius (122°F) in the tank, it gets tight — then 210 liters (55 gallons) would be needed.
Still, the difference to 300 liters (79 gallons) seems quite large to me. How does this look in practice?
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WilderSueden21 Feb 2024 19:50Approximately 40cm (16 inches) between the head and the shower head
We managed well with 5 people and a hot water tank of about 140 liters (37 gallons). However, this was with a gas heating system (50-55°C / 122-131°F) and it was quite rare for everyone to shower one after the other in a short time frame. Now, with just two of us and since daily showers are not necessarily needed, the hot water tank is obviously much too large.
Tolentino schrieb:
Does anyone else notice this effect? The same faucet, once with a fixed showerhead, once with a handheld shower, and despite a thermostatic mixer valve, the water temperatures differ? Yes, I know what you mean. With the rain shower, it feels like there is cooler air mixed in — that’s how I explain it.
Regarding the question: if the calculations are already tight, and we are talking about scenarios like warming up in the shower without a bathtub, maybe also using the small sink while the last person showers, I’m not building a house just to run these calculations because it might be tight and I’d have to make sacrifices since the family has its needs. -> 300 liters!
Showering habits are individual: I’m done after 2.5 minutes, while the shower only runs for 1.5 minutes. My husband showers for 15 minutes and doesn’t want to have to stop just because the water gets cold. Sometimes you want to save water, other times you need pressure… -> 300L!
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nordanney27 Feb 2024 19:03P.S. A beautiful Raindance 300mm (12 inch) showerhead, for example, has a flow rate of up to 17 liters (4.5 gallons) per minute at 3 bar (44 psi) water pressure. That means a lot of warm water is used.
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