22
CONNECTIONS
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 exchanger of the unit even if is installed,
as standard, a differential pressure switch that stops the unit if
the water flow rate is too low.
To adjust the water flow rate through the heat exchanger modi-
fy the speed of the pump by means of the 3 speed selector (if
present). For a more accurate adjustment it is reccomended the
installation of a valve on the outlet of the circuit.
It is also reccomended to install a filter on the inlet of each circuit
in order to avoid the entrance of foreign substances.
If as “Plant side flow rate management” option has been chosen
“Standard pump” or “High head pump”, the hydraulic circuit is
equipped with an expansion vessel. To mantain the circuit under
pressure a self-filling group, that automatically fills the circuit,
can be installed.
Suggestions for the hydraulic plant realization
Prepare the pipes with the minimum possible number of bends
in order to minimize pressure losses, and suitably support 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.
For reversible heat pumps, in order to avoid condensate gene-
ration, insulate all the pipes using steam barrier type material.
Finned coil condensate drainage
The condensate generated by the finned coil in heating mode is
collected in the tray obtained in the basement of the unit and can
be drained connecting a pipe to the fitting supplied as standard
with all the units.
Expansion vessel setting
The precharge pressure of the expansion vessel must be
adequate 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
relative 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 volume
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 appro-
priate 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
withstand 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
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
T
min
= 5°C , T
max
= 45°C
101,46
72,28
68,84
64,77
61,08
69,42
60,41
53,91
49,03
T
min
= -10°C , T
max
= 45°C
-
-
-
51,85
48,57
-
-
42,67
38,50
