Protections And Safeties - CombiSteel 7480 Serie Mode D'emploi

PROTECTIONS AND SAFETIES

Description of the protection and safety devices (fig. 10-A):
10-1 High pressure switch
It serves to interrupt the unit working if the system pressure is too high. After it has tripped, the high pressure
switch restarts automatically. The high pressure switch is fixed next to the compressor and there are two different
types of it: with fixed calibration or adjustable. In any case the tripping limit has to be 24 bar in the units with
R22 refrigerant and 28 bar in the units with R404A refrigerant. The differential is calibrated at 4 bar. It is standard
on the three-phase units, but it can be installed on all units on request.
10-2 Low pressure switch
It trips, stopping the unit, when the pressure in the suction circuit falls below the value at which it is calibrated.
Its restarting is automatic. Also this pressure switch lies next to the compressor and it can be with fixed regulation
or adjustable; in both cases the tripping limit is about -0,3 bar (in the units for cold room temperature of 0°C or
even higher, this limit could be slightly higher, maximum 0,1 bar). Normally the differential is 1 bar.
This pressure switch normally trips as a consequence of a failure or a working anomaly. However, if on specific
request, the compressor stop in vacuum is foreseen, the pressure switch always trips in the following cases:

stop as the programmed temperature value has been reached in the cold room,

compressor stop during the defrost phase.
10-3 Voltage monitor
It is an electronic instrument that is installed only on specific request. It serves to interrupt the unit supply when
the voltage on the line, at the beginning of the unit, is beyond the programmed limits.
These limits (maximum and minimum) can be regulated; the restarting is automatic when the normal conditions
are re-established with a delay that can be programmed on the instrument as well. The monitor is installed inside
the switchboard.
Instructions for the regulation (Fig. 12-1)

Programming of the counting/and delay time:
If the dip switch (A) is on the left and the dip switches (B), (C) and (D) are on the right, the delay time will
last about 6 minutes; if the dip switch (A) is put on the right, the time will be reduced to 9-10 seconds. To
this time 10, 20, 30 seconds can be added, by moving respectively the dip switches (B), (C), and (D) on the
left.

Change of the voltage limits:
If the dip switches (E) and (F) are positioned on the left, the monitor will switch on, if the indicated voltage
has a 12% higher or lower value than usual. It is possible to increase further the limits by 4% or 8%, moving
respectively the dip switches (E) and (F) on the right.
10-4 Fan protection thermocontact
All the fans used have inside this contact that, if correctly connected, interrupts the fan supply in case of
overheating of the corresponding motor winding. This device restarts automatically when the normal conditions
are restored; its trip value is fixed by the manufacturer. In some fans the thermocontact is already connected
inside the motor.
10-5 Fuses and automatic switches
Each of them has a specific function as indicated in the wiring diagram and in the corresponding legend provided
with the unit. If some apparatuses of the unit do not work, we suggest that you should control first of all the
efficiency of the fuses or of the automatic switches.
www.combisteel.com
13