Daikin EWWD VZ Series, Installation, Maintenance And Operating Manual

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The cooling circuit also installs an electronic overflow valve that, in addition to managing the level of refrigerant
in the heat exchangers and guaranteeing the correct operation of the compressor, also manages the PUMP-
DOWN function.
All the described components are managed by an innovative microprocessor control system that, by monitoring
all the machine operating parameters, optimizes operations.
A diagnostic system helps the operator in identifying alarm and fault causes.
WARNING
Before starting the compressors ensure that all valves are open and the closing caps are repositioned and
tightened.
Cooling cycle description
The low temperature refrigerant gas coming from the evaporator is sucked by the compressor and flows through
the electric motor, cooling it. It is subsequently compressed and during this phase the refrigerant mixes with the
oil, injected in the compressor, from the separator.
The high-pressure oil-refrigerant mixture is introduced inside the three-stage high efficiency oil separator which
performs the separation. The oil deposited on the bottom of the separator is sent, by pressure difference, to the
compressor again while the refrigerant separated from the oil is sent to the condenser.
The refrigerant fluid inside the condenser, which crosses the heat exchanger pipes in countercurrent,
desuperheats and starts to condense. The desuperheating heat and condensation is subtracted from the
condensation water which heats accordingly.
The condensed fluid at saturation temperature passes through the subcooling section, where it yields heat to
further increase cycle efficiency. The subcooled fluid flows through the overflow device which, through a
pressure drop, initiates the expansion process by vaporizing a part of the refrigerant liquid.
The result at this point is a mixture of liquid and gas at low pressure and temperature, poor in heat, which is
introduced into the evaporator.
The liquid-vapor refrigerant after being evenly distributed along the tube bundle exchanges heat with the water
to be cooled by reducing the temperature, and it gradually changes state until being fully evaporated.
Reaching the vapor state, it leaves the evaporator to be sucked by compressor again and restart the cycle.
Evaporator
The evaporator is a flooded shell and tube type with water flowing inside the tubes and the gas refrigerant
outside. Normally it does not require any maintenance and service. Should a tube require replacement, the old
tube can be removed and replaced. The water dome gasket must be replaced after tube cleaning and/or
replacement.
Condenser
The condenser is a shell and tube type with water flowing inside the tubes and the refrigerant outside. The
condenser tubes are externally finned and expanded on the tube plate. A subcooler is built into the condenser
on all units. Should a tube require replacement, the old tube can be removed and replaced. The water dome
gasket must be replaced after tube cleaning and/or replacement.
Expansion valve
The expansion valve is electrically controlled by the electronic controller by means of a specifically designed
electronic board. A special algorithm designed for machines with flooded evaporators, manages the refrigerant
flow to the evaporator according to machine operating parameters. In the event of blackout, the expansion valve
automatically closes thanks to an electric power accumulation system placed inside the electronic control board
(supercap)
Compressors
The refrigeration compressor is the single screw type with the rotation shaft directly coupled to the electric
motor.
The vapor flows through the electric motor cooling the windings before entering the suction ports. Sensors able
to constantly monitor temperature are located inside the motor windings to fully protect the motor against