12
Discharge gas thermostat DGT
(only for units with low temperature option)
A sensor in each compressor discharge line opens to shut down
the compressor if the discharge gas temperature exceeds the
preset level.
Cut out 146°C
Cut in 113°C
Crankcase heater
Each compressor is fitted with an electric resistance crankcase
heater which prevents any absorption of refrigerant by the
compressor lubricating oil when the compressor is shut down.
Each heater is held in place by a screw clip which must be
secure. Prolonged exposure of the heater to air will result in its
destruction. The heater is energized when the compressor is
switched off. Regularly check that the heater operates correctly
when the unit is shut down.
WARNING: Never open or disconnect any switch or circuit
breaker which will cut the supply to the heaters, unless the unit
is to be shut down for lengthy service or repair or for a
seasonal shut down. In all cases the heater must be energised
for at least 24 hours before a compressor is restarted.
Compressor protection circuit board (STARTERGUARD)
The purpose of this card is to monitor the compressor
operating environment, in particular:
•
the crankcase heaters
•
the contactors
•
the part winding start timer
•
the control wiring between these components
The status of the controlled components is displayed via three
different-coloured LEDs:
•
Green LED: correct operation
•
Orange LED: signals that the magnetic loop of the card
has detected the presence of a current, either in the
compressor crankcase heater or in the compressor motor.
If the green and orange LEDs are illuminated together,
this indicates that there is no fault.
•
Red LED - fault related to:
-
the heater, if the orange LED is not lit
-
the contactor or the power line of the compressor
motor, if the orange LED is lit
If a fault is detected, the compressor is shut down.
Power supply and resetting:
The STARTERGUARD card uses 24 V AC ± 10%, 50 Hz or
60 Hz. When a fault occurs, the 24 V supply must be
interrupted and then restored, in order to reset the card. The
green LED lights up.
Heat exchangers
Evaporator
Protection devices
Freeze-up prevention thermostat
The evaporator is protected against freeze-up. The protection is
provided by two sensors installed in the unit.
•
Significant undercharge (large bubbles in the sight glass,
drop in suction pressure).
-
Small units (charge below 20 kg per circuit).
After detection and repair completely drain the
refrigerant charge, using a refrigerant recovery unit,
then recharge completely, following the precautions
given above.
-
Large units (charge above 20 kg per circuit).
After detection and repair completely recharge the unit
as described above, operate it for a few minutes and
then let a specialist carry out a chromatographic
analysis to verify the composition of the blend
(range: R-32: 22-24%, R-125: 23-27%, R-134a: 50-54%).
Compressors
Checking the oil charge
Check the oil level and add or remove oil as necessary so that
the level is 1/8 to 3/8 up each sight glass with the compressor
running normally.
WARNING: Use only oils which have been approved for use in
refrigeration compressors. Never use oil which has been
exposed to air.
CAUTION: R-22 oils are NOT compatible with R-407C.
Recommended oil:
R-22 compressors:
-
Mineral oil, Carrier specification No. PP 33-2
-
Suniso 3 GS (Sun Oil Co)
-
Capella WF 32-150
-
Clavus G 32 (Shell Oil Co)
-
Gargoyle Artic (Mobil Oil) - original charge
R-407C compressors:
-
Oil, Carrier specification No. PP 47-26
-
Mobiloil EAL 68 - Carrier reference 470EE as original
charge, in 5 liter containers
WARNING: All fixing devices and fittings which may have
been removed during servicing must always be replaced upon
completion of the work and before restarting the unit.
Tightening torques to be applied
Description
Diameter, mm
Torque, Nm
Discharge valve
M16
135-140
Cylinder head
M12
75-87
Suction and liquid line flange
M12
75-87
Suction valve
M16
135-140
Compressor motor protection
Circuit breaker
Calibrated, thermo-magnetic, manually reset circuit breaker to
protect the motor against locked rotors and excessive current
draw. It also protects against overcurrents up to the trip
capacity indicated on the wiring diagram.
WARNING: Never bypass a circuit breaker or increase its
setting. If a circuit breaker trips, find out why it has done so
and correct the problem before resetting the breaker.
