18
Air-to-water Heat Pump
7.3 Water volume and expansion vessel pressure
2.5
2.0
1.5
1.0
0.5
Notes
0.0
0
50
100 150 200 250 300 350 400
Maximum total water volume(liter)
(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.
7.4 The method of calculating the charging pressure of expansion vessel
The method of calculating the charging pressure of expansion vessel needed to be adjusted is as follows.
During installation, if the volume of water system has changed, please check if the pre-set pressure of the
expansion vessel needs to be adjusted according to the following formula:
Bar(H ---the difference between installing location of indoor unit and the highest spot of
water system.)
Ensure that the volume of water system is lower than the maximum volume required in the above figure. If it
exceeds the range, the expansion vessel does not meet the installing requirement.
Installation height
1
difference
Water volume
<280L
>280L
<7 m
Adjustment is not necessary
1. Pre-set pressure needs to be adjusted
according to the above formula.
2. Check if the water volume is lower
than the maximum water volume. (with
help of the above figure)
<7 m
1. Pre-set pressure needs to be adjusted
according to the above formula.
2. Check if the water volume is lower than the
maximum water volume. (with help of the above
figure)
The expansion vessel is too small and
adjustment is not available.
Note
(a) Installation height difference: the difference between installing location of indoor unit and the highest spot
of water system
;
if the indoor unit is located at the highest point of the installation
,
the installation height
difference is considered 0m
.
Example 1: The indoor unit is installed 5m below the outdoor unit and the total volume of the water system is
100L.
Referring to the above figure, it is not necessary to adjust the pressure of the expansion vessel.
Example 2: The indoor unit is installed on the highest spot of the water system and the total water volume is
SPLIT TYPE
Pre
-pr
es
sur
e
in
e
xpens
ion
v
ess
el
(B
ar
)
