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?
BackSteinGotik schrieb:
With 300 liters (79 gallons), I guess you would keep about 100 liters (26 gallons) warm for nothing most of the year,If the storage tank is well insulated, it only heats up what has been used. My main reason would be an integrated 200 liters (53 gallons) storage in the heat pump, or a separate 300 liters (79 gallons) tank, so one less device.
200 liters (53 gallons) is enough for us; the heat pump will heat up more if it gets tight.
We also have a 190 L (50 US gallons) built-in tank. For the two of us, that’s more than enough. Only when our daughters visit (both with long hair) do I refill the hot water storage briefly in the morning and evening, about 1 hour each time, which is sufficient. That way, everyone has plenty of hot water. When all the ladies are in the house, it can sometimes get tight (cold).
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WilderSueden20 Feb 2024 20:56Tolentino schrieb:
But a shower temperature of 35°C (95°F) and washing your hair in 3.5 minutes? Did you all go to military training school?I don’t have 35 degrees myself, but a few years ago at a campsite I had a 5-minute shower token. Anyone familiar with Swabians knows what happens next. The token is paid for, so it’s used fully, even if you’re technically done showering. The warm water lasted quite a long time after that...
Camping at a campsite is one thing, but at home, you want to have comfort.
Okay, I need to stop my usual shower routine for a moment. But I would bet it’s a solid 5 minutes, and that’s without dawdling.
The temperature on the thermostatic mixing valve is set to 42°C (108°F). Whether that is accurate, I can’t say, and the water from the rain shower feels much colder than from the handheld showerhead. I think this is due to the rain effect and the fact that the water falls a longer distance from the overhead shower to me, but I wouldn’t have expected the difference to be so extreme.
Does anyone else know this effect? So, the same valve, once with a fixed showerhead and once with a handheld showerhead, and despite the thermostatic valve, different temperatures?
Okay, I need to stop my usual shower routine for a moment. But I would bet it’s a solid 5 minutes, and that’s without dawdling.
The temperature on the thermostatic mixing valve is set to 42°C (108°F). Whether that is accurate, I can’t say, and the water from the rain shower feels much colder than from the handheld showerhead. I think this is due to the rain effect and the fact that the water falls a longer distance from the overhead shower to me, but I wouldn’t have expected the difference to be so extreme.
Does anyone else know this effect? So, the same valve, once with a fixed showerhead and once with a handheld showerhead, and despite the thermostatic valve, different temperatures?
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WilderSueden21 Feb 2024 19:31We have both set on the faucet, adjusted to 38°C (100°F). It feels the same.
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