Daikin Altherma 3 HT - Selecting the Volume and Desired Temperature for the DHW Tank

6 | Application guidelines
Installer reference guide
50
EPRA14~18D + ETVH/X16S18+23E
Daikin Altherma 3 H HT F
4P644737-1A – 2022.03
6.4.2 Selecting the volume and desired temperature for the DHW tank
People experience water as hot when its temperature is 40°C. Therefore, the DHW
consumption is always expressed as equivalent hot water volume at 40°C.
However, you can set the DHW tank temperature at a higher temperature
(example: 53°C), which is then mixed with cold water (example: 15°C).
Selecting the volume and desired temperature for the DHW tank consists of:
1 Determining the DHW consumption (equivalent hot water volume at 40°C).
2 Determining the volume and desired temperature for the DHW tank.
Determining the DHW consumption
Answer the following questions and calculate the DHW consumption (equivalent
hot water volume at 40°C) using typical water volumes:
Question Typical water volume
How many showers are needed per
day?
1shower = 10min×10l/min = 100l
How many baths are needed per day? 1bath = 150l
How much water is needed at the
kitchen sink per day?
1sink = 2min×5l/min = 10l
Are there any other domestic hot water
needs?
—
Example: If the DHW consumption of a family (4 persons) per day is as follows:
▪ 3 showers
▪ 1 bath
▪ 3 sink volumes
Then the DHW consumption = (3×100l)+(1×150l)+(3×10l)=480l
Determining the volume and desired temperature for the DHW tank
Formula Example
V
1
=V
2
+V
2
×(T
2
−40)/(40−T
1
) If:
▪ V
2
=180l
▪ T
2
=54°C
▪ T
1
=15°C
Then V
1
=280l
V
2
=V
1
×(40−T
1
)/(T
2
−T
1
) If:
▪ V
1
=480l
▪ T
2
=54°C
▪ T
1
=15°C
Then V
2
=307l
V
1
DHW consumption (equivalent hot water volume at 40°C)
V
2
Required DHW tank volume if only heated once
T
2
DHW tank temperature
T
1
Cold water temperature