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Application guidelines
Installer reference guide
52
ERRA08~12E + ELVH/23E
Daikin Altherma 3 R MT F
4P708474-1 – 2023.05
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
