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Checking the water volume and expansion vessel
pre-pressure
The unit is equipped with an expansion vessel of 12 litre which has a
default pre-pressure of 1 bar.
To assure proper operation of the unit, the pre-pressure of the
expansion vessel might need to be adjusted and the minimum and
maximum water volume must be checked.
1
Check that the total water volume in the installation, excluding
the internal water volume of the unit, is 20 l minimum.
In most applications this minimum water volume will have a
satisfying result.
In critical processes or in rooms with a high heat load
though, extra water volume might be required.
When circulation in each space heating/radiator loop is
controlled by remotely controlled valves, it is important that
this minimum water volume of 20 l is kept even if all the
valves are closed.
Example
1
11
2
3
11
5
1
Outdoor unit
2
Indoor unit
3
Refrigerant heat
exchanger
4
Water heat exchanger
5
Compressor
6
Pump
7
Shut-off valve
8
Collector (field supply)
9
By-pass valve
(field supply)
Installation manual
13
A
C1
4
6
7 7 8
9
M3
M2
M1
10
Radiator (field supply)
11
Electronic expansion
valve
C1
Remote controller
M1...M3
Individual motorized valve
to control loop radiators
(field supply)
T1...T3
Individual room
thermostat (field supply)
A
Installation space
B
Living room
2
Using the table and instructions below, determine if the
expansion vessel pre-pressure requires adjustment and
determine if the total water volume in the installation is below the
maximum allowed water volume.
Installation
height
difference
≤7 m
>7 m
B
(a) Installation height difference: height difference (m) between the highest point
of the water circuit and the indoor unit. If the indoor unit is located at the
10
highest point of the installation, the installation height is considered 0 m.
Calculating the pre-pressure of the expansion vessel
The pre-pressure (Pg) to be set depends on the maximum installation
T3
height difference (H) and is calculated as below:
Pg=(H/10+0.3) bar
T2
Checking the maximum allowed water volume
To determine the maximum allowed water volume in the entire circuit,
proceed as follows:
T1
1
Determine
corresponding maximum water volume using the graph below.
2
Check that the total water volume in the entire water circuit is
lower than this value.
If this is not the case, the expansion vessel inside the indoor unit is
too small for the installation.
2.5
2
1.5
1
0.5
0.3
0.0
0 20
50
Water volume
65°C ≤270 l
65°C >270 l
(a)
80°C ≤180 l
80°C >180 l
Actions required:
• pre-pressure must be
No pre-pressure adjustment
required.
• check if the water volume
Actions required:
• pre-pressure must be
increased, calculate
according to
"Calculating
the pre-pressure of the
Expansion vessel of the unit
expansion vessel"
too small for the installation.
• check if the water volume
is lower than maximum
allowed water volume
(use graph below)
for
the
calculated
pre-pressure
100
150
200
250
300
maximum water volume [l]
= pre-pressure
= maximum water volume
= increase pre-pressure vessel volume
= decrease pre-pressure vessel volume
Indoor unit for air to water heat pump system
decreased, calculate
according to
"Calculating
the pre-pressure of the
expansion vessel"
is lower than maximum
allowed water volume
(use graph below)
(Pg)
the
350
400
450
EKHBRD011~016ADV17+Y17
4P402191-1B – 2017.09
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