7
SECTION 1 – Unit Description
Zanotti Z120 refrigeration systems are designed for
low and medium temperature applications on vans
and small-sized trucks with one compartment. There
are several basic models:
•
134a systems and 404a systems
•
Road only and Road with standby
equipped
The system consists of two separate assemblies: the
condenser and the evaporator.
1.1 CONDENSING SECTION
The condenser has a unique design that allows it to be
mounted horizontally on the roof, or on the front of
the vehicle box.
1.1.1 Condenser coil
The condenser is mini-tube type and acts as heat
exchanger in which the compressed refrigerant gas is
condensed into a liquid and lowered in temperature.
A fan mounted in the condensing section provides air
movement on the condenser.
1.1.2 Filter drier
The drier is a cylindrical shell containing a drying
agent and screen. It’s installed in the liquid line and
functions to keep the system clean and remove
moisture from the refrigerant.
1.1.3 Compressor
The compressor is a reciprocating two cylinder. This
compressor is mounted in the center of the
condensing unit and is driven by belt from either the
12/24 vdc motor or the vac electric standby motor
Compressor operation is controlled by the
thermostat, which energizes the motor during road
operation or starts the electric motor and energizes
the ac motor on electric standby operation. The
refrigeration system is protected by a high-pressure
cut-out switch and a low-pressure cut-out switch.
When plugged into standby power, road operation is
automatically locked out. If the vehicle engine is
turned on while the power cord is still plugged into a
power receptacle, the unit will show an alarm signal;
the 12/24 vdc motor cannot be started until the power
cord is unplugged from the unit as the selection of road
operation or standby operation is automatic.
1.1.4 Receiver
Liquid refrigerant from the condenser is delivered to the
receiver. The receiver serves as a liquid reservoir when
there are surges due to load changes in the system; as a
storage space when pumping down the system and as a
liquid seal against the entrance of refrigerant gas into the
liquid line.
1.1.5 High-pressure switch
The High-Pressure Cut-out Switch is a pressure sensitive
switch. If the discharge pressure rises above the switch’s
opening pressure, the switch opens the circuit to stop the
unit. When the discharge pressure falls below the switch’s
closing pressure, the switch closes to restart the unit.
1.1.6 CPR valve
The compressor pressure regulation valve (CPR valve) is
installed on the suction line to regulate the suction
pressure entering the compressor. The CPR valve protects
the compressor and is set to limit the maximum suction
pressure. For CPR settings refer to section 4.16
1.1.7 Electric standby operation
During electric standby operation, the thermostat controls
the operation of the unit by energizing and de-energizing
the power relay and the electric relays. The thermostat
places the unit in cool by energizing the Power relay and
the electric relays.
1.1.8 DC Motor
The DC motor drives the compressor in Road Mode. When
the vehicle is turned on and the In-Cab controller is turned
on the KMC relay is activated through the CPU Board
1.1.9 AC Motor
The AC motor drives the compressor in Stand by Mode.
When the vehicle is turned off and the electric stand by
plug is plugged in the CPU board will activate the K1
Contactor energizing the electric motor
