Daikin EKHBX030BA Installation Manual page 17

Checking the water volume and expansion vessel pre-
pressure
The unit is equipped with an expansion vessel of 2.6 gallons (10 litre)
which has a default pre-pressure of 14.5 psi (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 indoor unit, is 2.6 gallons (10 l)
minimum. Refer to "Technical specifications" on page 42 to
know the internal water volume of the indoor unit.
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.
NOTE When circulation in each space heating loop is
controlled by remotely controlled valves, it is important
that this minimum water volume is kept even if all the
valves are closed.
Example
1 2 3 4
1 Outdoor unit
2 Indoor unit
3 Heat exchanger
4 Pump
5 Shut-off valve
6 Collector (field
supply)
7 Shut-off valve
2 Using the table below, determine if the expansion vessel pre-
pressure requires adjustment.
EKHBH/X030BA
Indoor unit for air to water heat pump system
4PW62568-1 – 07.2010
5 6
T1 T2 T3
M1 M2 M3
7 FHL1
FHL2
FHL3
8 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
(field supply)
3 Using the table and instructions below, determine if the total
water volume in the installation is below the maximum allowed
water volume.
Installation Water volume
height
≤
(a)
74 gallons (280 l)
difference
≤
23 ft
No pre-pressure adjustment
(≤
required.
7 m)
Actions required:
• pre-pressure must be increased,
calculate according to "Calculating
>23 ft
the pre-pressure of the expansion
(>7 m)
vessel"
• check if the water volume is lower
than maximum allowed water volume
(use graph below)
(a) Installation height difference: height difference (ft)(m) between the highest point
of the water circuit and the unit. If the unit is located at the highest point of the
installation, the installation height is considered 0 ft (0 m).
Calculating the pre-pressure of the expansion vessel
The pre-pressure (Pg) to be set depends on the maximum
installation height difference (H) and is calculated as below:
Pg =(H /32+0.3)x14.5 psi
(psi) (ft)
Pg =(H /10+0.3) bar
(bar) (m)
8
Checking the maximum allowed water volume
To determine the maximum allowed water volume in the entire circuit,
proceed as follows:
1 Determine for
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 unit is too small
for the installation.
40
2.4 34.8
30
2
25
1.5
20
1 14.5
10
0.5
0.3 4.4
0 2.6
10 20 30
0 10 50 100
pre-pressure
maximum water
volume
Example 1
The unit is installed 16.4 ft (5 m) below the highest point in the water
circuit. The total water volume in the water circuit is 26.4 gallons
(100 l).
In this example, no action or adjustment is required.
>74 gallons (280 l)
Actions required:
• pre-pressure must be decreased,
calculate according to "Calculating
the pre-pressure of the expansion
vessel"
• check if the water volume is lower
than maximum allowed water volume
(use graph below)
Expansion vessel of the unit
too small for the installation.
the calculated pre-pressure
74
40 50 60 70 80 90 100 110
150 200 250 280 300 350 400
maximum water volume
= pre-pressure
= maximum water volume
Installation manual
(Pg) the
[gallons]
120
[l]
450
15