Heat Pump
Unitherm 3 R32
22
7.7 Water volume and expansion vessel pressure
Pre-pressure in expension vessel(Bar)
Maximum total water volume(liter)
2.5
2.0
1.5
1.0
0.5
0.0
0
50
100
150
200
250
300
350
400
Notes
(a)
The expansion vessel is 10 liter and 1bar pre-pressurized;
(b)
Total water volume of 280 liter is default; if total water is changed because of installation condition, the pre-
pressure should be adjusted to secure proper operation. If the indoor unit is located at the highest position,
adjustment is not required;
(c)
Minimum total water volume is 20 liter;
(d)
To adjust pre-pressure, use nitrogen gas by certificated installer.
7.8 Selection of expansion vessel
Formula:
V--- Volume of expansion vessel
C--- Total water volume
P
1
--- Pre-set pressure of expansion vessel
P
2
-- The highest pressure during running of the system (that is the action pressure of safety valve.)
e---The expansion factor of water (the difference between the expansion factor of the original water temperature
and that of highest water temperature.)
Water expansion factor in different temperature
Temperature(°C)
Expansion factor e
0
0.00013
4
0
10
0.00027
20
0.00177
30
0.00435
40
0.00782
45
0.0099
50
0.0121
55
0.0145
60
0.0171