ᐅ Dimension of Hot Water Storage Tank

Created on: 28 Jun 2016 08:46
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McEgg
A quick question. The current offer from the house building company includes the following regarding heating:

"A split air-to-water heat pump (manufacturer Viessmann, Junkers, or Wolff) with a 300-liter (79-gallon) hot water tank (without solar). The system is complete with all control and regulation equipment."

The house will have underfloor heating on the ground floor and first floor, with about 170 m² (1830 sq ft) of living space. There are currently three people living in the house (though it’s possible that there may be children in the future).

Is a 300-liter (79-gallon) hot water tank appropriately sized? The shower will be used significantly more than the bathtub...
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ErikErdgas
29 Jun 2016 12:05
Hello McEgg,

just a rough calculation without considering losses, etc.: the 300-liter (79 gallons) tank has an energy content of approximately 15 kWh. Depending on the showerhead and temperature, you of course draw different amounts of heat. With a heat output of 15 kW, the tank would provide hot water for about one hour.

This, of course, needs to be adjusted for losses, the decreasing temperature, possible reheating by the heat source, and so on, but maybe this gives a rough idea.

Best regards, Erik from moderne.Heizung
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Sebastian79
29 Jun 2016 12:47
I cannot follow your explanation...
McEgg29 Jun 2016 14:56
Me neither. However, I would be interested in an explanation.
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Legurit
29 Jun 2016 15:00
He means that a 15 kW heater heats the tank quickly again, so it doesn't really matter anyway.
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ErikErdgas
1 Jul 2016 13:42
Hello,

with the calculation, I wanted to roughly show how much heat output can be drawn from the storage tank and for how long, assuming it is fully charged. Therefore, I also believe that the storage tank should easily be sufficient for the described scenario.

Since nothing was mentioned about the heat generator or its design, I assumed that a shower requires around 15 kW of power, which is taken from the storage tank.

Best regards, Erik from moderne.Heizung
McEgg1 Jul 2016 15:05
Thanks again.