Hot water storage size for brine heat pump and 4 people

  • Erstellt am 2016-10-26 21:25:34

rabudde

2016-10-26 21:25:34
  • #1
Hello,

I know it depends on many factors, but I have to make a decision within the next 2 days. We are building a bungalow (164 sqm) and included in the offer is a Vaillant flexoCompact 88/4. This has a 185L hot water tank. Now, we have been offered to use a separate 270L stainless steel tank from Vaillant instead of the integrated one for an additional 800 EUR. We are 4 people, including 2 children in elementary school age — so water consumption will certainly increase. However, we generally shower and bathe rarely — for now. Unfortunately, I cannot quantify what our actual consumption would be. The last years show a cold water consumption for hot water of 23-27 cbm in the utility bill. The house will have two showers (HansGrohe Croma Select E with a flow rate of 14L/min) and a bathtub with about 170L net water volume. Shower and bath temperatures should be guaranteed at a minimum of 40°C.
Now I thought: bigger tank — lower temperature necessary. The house will have a circulation line, and I believe the bigger tank can somewhat compensate for losses along the way. I am torn about what is more efficient in the long run considering hygiene (if we put the purchase price aside). 185L or 270L? Any tips?
 

Legurit

2016-10-26 21:31:25
  • #2
We have the mentioned integrated storage and are doing quite well for the time being – however, after 2 cycles without reheating in between, the water is then too little for the bathtub. But there is nothing wrong with about 270 L. Large storage tanks have correspondingly higher losses – so this is a second argument besides the acquisition costs.
 

Grym

2016-10-26 21:31:55
  • #3
Considering hygiene: A hygiene reservoir.
 

toxicmolotof

2016-10-26 22:15:18
  • #4
How much water can the boiler heat during operation without the heating element turning on? Without knowing this variable, everything else is just a guess.
 

Grym

2016-10-26 22:45:29
  • #5
1,162 W*h/(kg*K)
=> From 20 to 40 degrees per liter: 23.24 Wh = 0.02324 kWh
=> Power 8.9 to 9.0 kW (at 35 or 55 degrees water temperature hot water)
=> 383 liters of hot water at 40 degrees per hour
=> Or 191 liters of hot water at 60 degrees, which is then mixed with cold water at 20 degrees = 383 liters of water at 40 degrees
=> 6.4 liters of shower/bath water per minute
=> Shower consumption: 14 liters per minute
=> 170 liters bathtub needs 27 minutes to warm up

=> All my amateur calculations :-)
 

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