ᐅ Hot Water Storage Tank Size for Ground Source Heat Pump and 4-Person Household
Created on: 26 Oct 2016 21:25
R
rabuddeHello,
I know it depends on many factors, but I need to make a decision within the next 2 days. We are building a bungalow (164 sqm (1,766 sq ft)) and the offer includes a Vaillant flexoCompact 88/4. This has a 185 L (49 gallon) hot water tank. Now, we have been offered to use a separate 270 L (71 gallon) stainless steel tank from Vaillant instead of the integrated one for an additional 800 EUR. We are 4 people, including 2 children of primary school age – so water consumption will likely increase. However, we generally shower and bathe rarely – at least for now. Unfortunately, I can’t really estimate what our actual consumption will be. Recent years’ utility bills show a cold water consumption for hot water of 23–27 m³ (810–952 cubic feet). The house will have two showers (HansGrohe Croma Select E with a flow rate of 14 L/min (3.7 gallons/min)) and a bathtub with approximately 170 L (45 gallon) net water volume. Shower and bath temperatures should be maintained at a minimum of 40°C (104°F).
Now I’m thinking: bigger tank means lower temperature necessary. The house will have a circulation line, and I believe the larger tank could help compensate some distribution losses along the way. I’m torn between which option might be more efficient in the long run, considering hygiene, if we put aside the purchase price. 185 L or 270 L? Any tips?
I know it depends on many factors, but I need to make a decision within the next 2 days. We are building a bungalow (164 sqm (1,766 sq ft)) and the offer includes a Vaillant flexoCompact 88/4. This has a 185 L (49 gallon) hot water tank. Now, we have been offered to use a separate 270 L (71 gallon) stainless steel tank from Vaillant instead of the integrated one for an additional 800 EUR. We are 4 people, including 2 children of primary school age – so water consumption will likely increase. However, we generally shower and bathe rarely – at least for now. Unfortunately, I can’t really estimate what our actual consumption will be. Recent years’ utility bills show a cold water consumption for hot water of 23–27 m³ (810–952 cubic feet). The house will have two showers (HansGrohe Croma Select E with a flow rate of 14 L/min (3.7 gallons/min)) and a bathtub with approximately 170 L (45 gallon) net water volume. Shower and bath temperatures should be maintained at a minimum of 40°C (104°F).
Now I’m thinking: bigger tank means lower temperature necessary. The house will have a circulation line, and I believe the larger tank could help compensate some distribution losses along the way. I’m torn between which option might be more efficient in the long run, considering hygiene, if we put aside the purchase price. 185 L or 270 L? Any tips?
We have the mentioned integrated storage and are currently managing quite well with it – however, after two uses without reheating in between, the water is then just barely enough for the bathtub.
Around 270 liters (70 gallons) is reasonable, though.
Large storage tanks have correspondingly higher heat losses – so that’s another point to consider besides the initial cost.
Around 270 liters (70 gallons) is reasonable, though.
Large storage tanks have correspondingly higher heat losses – so that’s another point to consider besides the initial cost.
T
toxicmolotof26 Oct 2016 22:15How much water can the boiler heat during continuous operation without the electric heating element activating? Without knowing this variable, everything else is just guesswork.
1,162 Wh/(kg*K)
=> From 20 to 40 degrees Celsius (68 to 104°F) per liter: 23.24 Wh = 0.02324 kWh
=> Power output 8.9 to 9.0 kW (at 35 or 55 degrees Celsius (95 or 131°F) hot water temperature)
=> 383 liters (101 gallons) of hot water at 40 degrees Celsius (104°F) per hour
=> Or 191 liters (50 gallons) of hot water at 60 degrees Celsius (140°F), which is then mixed with cold water at 20 degrees Celsius (68°F) = 383 liters (101 gallons) of water at 40 degrees Celsius (104°F)
=> 6.4 liters (1.7 gallons) of shower/bath water per minute
=> Shower consumption: 14 liters (3.7 gallons) per minute
=> 170 liters (45 gallons) bathtub takes 27 minutes to heat up
=> All my amateur calculations :-)
=> From 20 to 40 degrees Celsius (68 to 104°F) per liter: 23.24 Wh = 0.02324 kWh
=> Power output 8.9 to 9.0 kW (at 35 or 55 degrees Celsius (95 or 131°F) hot water temperature)
=> 383 liters (101 gallons) of hot water at 40 degrees Celsius (104°F) per hour
=> Or 191 liters (50 gallons) of hot water at 60 degrees Celsius (140°F), which is then mixed with cold water at 20 degrees Celsius (68°F) = 383 liters (101 gallons) of water at 40 degrees Celsius (104°F)
=> 6.4 liters (1.7 gallons) of shower/bath water per minute
=> Shower consumption: 14 liters (3.7 gallons) per minute
=> 170 liters (45 gallons) bathtub takes 27 minutes to heat up
=> All my amateur calculations :-)
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