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Fig. c -- Sizing of the expansion vessel
The total volume of the expansion vessel is calculated with the following formula:
C x e
V =
Pi
1 - -
Pf
where:
---
C=quantity of water inside the system expressed in litres
---
e=water expansion coefficient, with water at 10ûC as a reference
---
Pi=absolute pressure of initial charging, equivalent to the vessel pre ---charge pressure (typical value
2.5 bara)
---
Pf=absolute final tolerated pressure, lower than the operating pressure of the safety valve calibration
pressure (typical value 4.0 bara).
Use the values of the water expansion coefficient indicated in the table below:
H
O T [°C]
2
10
20
30
40
50
3.3 --- Electrical connections
1) Before proceeding with the electrical connections, ensure
that:
all electrical components are undamaged;
S
all terminal screws are tight;
S
the supply voltage and frequency are in accordance with
S
the rating (with tolerance in accordance with IEC 8---6
norms, March 1990)
the allowed phase to phase variability is 3% maximum
S
(see Fig. d). Variability in excess of 3% invalidates the
guarantee.
2) Supply cable connections (see Tab. 6):
Connect the cable to the supply terminals.
S
Use appropriately sized 3---pole cable. An earth wire
S
must also be connected.
After having opened the passage in the framework (pre ---
S
punched knock ---outs) for the supply line entry, restore
the original degree of protection using suitable accesso-
ries for the wiring and junction boxes.
Fig. d -- Example of calculating phase
to phase variability
1) The 400 V supply has
the following variability:
RS = 388 V
ST = 401 V
RT = 402 V
2) The average voltage is:
388 + 401 + 402
3
3) The maximum deviation from the average is:
402 --- 397 = 5 V
4) The phase to phase variability is:
5
x 100 = 1.26 (acceptable)
397
Note:
The power supply should never be disconnected, except when
performing maintenance.
3
Density [kg/m
]
999.6
997.9
995.6
992.2
988.1
R S T
= 397
Expansion coefficient "e"
--- --- ---
0.0017
0.0040
0.0075
0.0116
Operate (open) the main switch before carrying out any mainte-
nance work on electrical components.
Note:
It is forbidden to work on the electrical components without
using insulating platforms, and in the presence of water or fog
or mist.
Note:
The supply to the external pump assembly must be made before
starting the chiller and must be kept on as long as the chiller is
in use. Incorrect operation will cause the unit to lock ---out be-
cause of the internal protections (flow switch intervention).
Note:
The compressors are equipped with an electronic protection de-
vice blocking their start if the phase sequence is not correct, or
stopping their operation if a thermal relay intervenes. This device
is essential for the integrity of the mechanical and electrical com-
ponents of the compressors. Reset the standard functions by
isolating this device and removing the causes of the lock ---out.
Note:
The chillers are equipped with their own microprocessor control
adjustment. The use of the remote ON ---OFF input (located in
the electric panel terminal board) as a system temperature con-
trol element is forbidden.
4 --- Start---Up and Operation
4.1 --- Initial check
1) Check all water connections.
2) Open the shut---off valve on the liquid line.
3) Ensure that the intake pressure is higher than 4.0 bar; if this
is not the case, prolong pre ---heating of the compressor (if
possible) and check that the refrigerant shut---off valve is
properly sealed, see Fig. 9.
4) Open all isolating valves and/or water ball valves.
5) In case of climates with temperatures below zero degrees C,
make sure the chilled water circuit is filled with the correct
concentration of water/glycol.
6) Bleed all air out of the chilled water circuit.
7) Verify the water flow rate and its direction.
8) Ensure that the thermal load is sufficient for start---up.
Caution:
The ambient air temperature probe must be positioned in the
shade and protected against the weather.
4
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