Formula To Calculate The Expansion Vessel Pre-Pressure; To Check The Water Volume And Flow Rate - Daikin Altherma EHVH08SU18CB6W Installer's Reference Manual

▪ Domestic hot water tank kit – Secondary return. Where the
secondary return circuits are used, an additional expansion vessel
may be required.
▪ Thermostatic mixing valves. In accordance with the applicable
legislation, it may be necessary to install thermostatic mixing
valves.
▪ Hygienic measures. The installation must be in compliance with
the applicable legislation and may require additional hygienic
installation measures.
▪ Recirculation pump. In
legislation, it may be required to connect a recirculation pump in
between the hot water end point and the recirculation connection
of the domestic hot water tank.
c
a b
d
a Recirculation connection
b Hot water connection
c Shower
d Recirculation pump
6.4.2 Formula to calculate the expansion vessel
pre-pressure
The pre-pressure (Pg) of the vessel depends on the installation
height difference (H):
Pg=0.3+(H/10) (bar)
6.4.3

To check the water volume and flow rate

The indoor unit has an expansion vessel of 10 litre with a factory-set
pre-pressure of 1 bar.
To make sure that the unit operates properly:
▪ You must check the minimum and maximum water volume.
▪ You might need to adjust the pre-pressure of the expansion
vessel.
Minimum water volume
Check that the total water volume in the installation is minimum
10 litre, the internal water volume of the indoor unit NOT included.
INFORMATION
In critical processes, or in rooms with a high heat load,
extra water might be required.
NOTICE
When circulation in each space heating/cooling loop is
controlled by remotely controlled valves, it is important that
the minimum water volume is guaranteed, even if all of the
valves are closed.
a b c d f
T1
M1
e f
FHL1
a Outdoor unit
ERLQ004~008CA + EHVH04+08SU18+26CB6W
Daikin Altherma – Low temperature split
4P449978-1B – 2018.07
accordance with the applicable
g h
T2 T3
M2 M3
FHL2
FHL3
b Indoor unit
c Heat exchanger
d Backup heater
e Pump
f Shut-off valve
g Collector (field supply)
h By-pass valve (field supply)
FHL1...3 Floor heating loop (field supply)
T1...3 Individual room thermostat (optional)
M1...3 Individual motorised valve to control loop FHL1...3 (field
supply)
Maximum water volume
Use the following graph to determine the maximum water volume for
the calculated pre-pressure.
a
2.5
2
1.5
1
0.5
0.3
0 10
50 100 150 200
a Pre-pressure (bar)
b Maximum water volume (l)
Example: Maximum water volume and expansion vessel pre-
pressure
Installation
height
≤280 l
(a)
difference
≤7 m No pre-pressure
adjustment is required.
>7 m Do the following:
▪ Increase the
pressure according to
the
installation
difference. The
pressure
increase by 0.1 bar for
each metre above 7 m.
▪ Check if the water
volume does
exceed the maximum
allowed water volume.
(a) This is the height difference (m) between the highest point
of the water circuit and the indoor unit. If the indoor unit is
at the highest point of the installation, the installation height
is 0 m.
Minimum flow rate
Check that the minimum flow rate (required during defrost/backup
heater operation) in the installation is guaranteed in all conditions.
6 Preparation
250 300 350 400 450
Water volume
>280 l
Do the following:
▪ Decrease the pre-
pressure according to
the required installation
height difference. The
pre-pressure should
decrease by 0.1 bar for
each metre below 7 m.
▪ Check if the water
volume does NOT
exceed the maximum
allowed water volume.
The expansion vessel of
the indoor unit is too
pre-
small for the installation.
In this case, it is
required
recommended to install
height
an extra vessel outside
pre-
the unit.
should
NOT
Installer reference guide
27
b