CONNECTIONS
23
Hydraulic connections
To design properly the hydraulic system respect the local
safety regulations in force.
It is always necessary to guarantee an appropriate water flow
through the plate heat exchangers of the unit even if on both
the hydraulic circuits (source side and plant side) is installed,
as standard, a flow switch that stops the unit if the water flow
rate is too low.
To adjust the water flow rate through the heat exchangers
modify the speed of the pump by means of the 3 speed selec-
tor. For a more accurate adjustment it is reccomended the
installation of a valve on the outlet of each circuit.
It is also reccomended to install a filter on the inlet of each cir-
cuit in order to avoid the entrance of foreign substances.
The hydraulic circuit on the plant side is equipped with safety
valve and expansion vessel. To mantain the circuit under pres-
sure a self-filling group, that automatically fills the circuit, can
be installed.
The hydraulic circuit on the source side is equipped with
expansion vessel. If it is used as a closed circuit it is neces-
sary to install an adequate safety valve (maximum setting 6
bar).
Suggestions for the hydraulic plant realization
Prepare the pipes with the minimum possible number of
bends in order to minimize pressure losses, and suitably sup-
port them to prevent excessive stresses at the connections of
the unit.
Install shut-off valves near the components that need mainte-
nance, to allow their replacement without having to drain the
system.
Provide manual or automatic valves in the highest part of the
circuit to vent the air.
Make sure there are no leaks before insulating the pipes and
filling the system.
In order to avoid condensate generation insulate all the pipes
on the source side (and also on the plant side for reversible
heat pumps) using steam barrier type material.
Brine solutions
When the unit is used as a brine-water heat pump, the source
side hydraulic circuit must be filled with a brine solution able to
guarantee a freezing temperature lower than the minimum
expected operating temperature. In order to guarantee the
unit to work inside the whole operating range declared, a free-
zing temperature not higher than -15°C is required.
The brine solution must be mixed before filling the circuit.
All the components used on the source side hydraulic circuit
must be suitable to work with the brine solution adopted.
Galvanized steel pipes are not to be used.
Expansion vessels setting
All the units are equipped with expansion vessels (source side
and plant side).
The precharge pressure of the expansion vessel must be ade-
quate to the total volume of the hydraulic circuit at which the
unit is connected.
The factory setting (p
VE-std
=
0,5 bar g) is the minimum value
necessary to avoid the presence of zones with a negative rela-
tive pressure inside the hydraulic circuit and the risk of pump
cavitation, supposing that no parts of the plant are placed at a
higher level than the one at which the unit is installed. In that
case the precharge pressure must be increased proportionally
to the elevation of the highest part of the plant according to the
following relation :
p
VE
= p
VE-std
+ H
max
/ 9,81
p
VE
:
expansion vessel precharge pressure [bar g]
H
max
elevation of the highest part of the plant referred to
the unit installation level [m]
The maximum value of the precharge pressure is equal to the
safety valve pressure set.
Increasing the precharge pressure, the maximum plant volu-
me supported by the expansion vessel of the unit is reduced :
V
I
= V
VE
· C
e
· [ 1 - ( 1 + p
VE
) / ( 1 + p
VS
) ]
V
I
:
plant volume supported by the expansion vessel [l]
V
VE
:
expansion vessel volume [l]
C
e
:
expansion coefficient
p
VS
:
safety valve pressure set [bar g]
If the real plant volume is higher than such calculated volume,
it is necessary to install an additional expansion vessel of
appropriate volume.
Once the hydraulic circuit has been filled, the pressure at the
expansion vessel must be slightly higher than the precharge
pressure.
If parts of the plant are placed at a lower level than the one at
which the unit is installed, verify that the components can with-
stand the maximum pressure that can be present.
Water
Ethylene glycol
(percentage by volume)
Propylene glycol
(percentage by volume)
10%
20%
30%
40%
10%
20%
30%
40%
Freezing temperature [°C]
0
-3,8
-8,9
-15,7
-24,9
-3,4
-7,4
-13,1
-21,5
C
e
Plant side (T
min
= 5°C , T
max
= 60°C)
58,63
47,80
45,24
42,82
40,61
45,47
39,96
35,82
32,88
Source side (T
min
= 5°C , T
max
= 45°C)
101,46
73,28
68,84
64,77
61,08
69,42
60,41
53,91
49,03
Source side (T
min
= -10°C , T
max
= 45°C)
-
-
-
51,85
48,57
-
-
42,67
38,50
Содержание HSW 11.1
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