Operation; Operator's Responsibilities; Description Of The Machine; Description Of The Refrigeration Cycle - Daikin EWYD-BZ Series Installation, Maintenance & Operation Manual

Operation

Operator's responsibilities

It is important that the operator is appropriately trained and becomes familiar with the system before operating the
machine. In addition to reading this manual, the operator must study the microprocessor operating manual and the wiring
diagram in order to understand start-up sequence, operation, shutdown sequence and operation of all the safety devices.
Read the VFD manual carefully.
During the machine's initial start-up phase, a technician authorized by the manufacturer is available to answer any
questions and to give instructions as to the correct operating procedures.
The operator is advised to keep a record of operating data for every installed machine. Another record should also be
kept of all the periodical maintenance and servicing activities.
If the operator notes abnormal or unusual operating conditions, he is advised to consult the technical service authorized
by the manufacturer.

Description of the machine

This machine, of the air-cooled condenser type, is made up of the following main components:
- Compressor: The state-of-the-art single-screw compressor of the Fr3100 series is of the semi-hermetic type and
utilises gas from the evaporator to cool the motor and allow optimal operation under any expected load conditions. The
oil-injection lubrication system does not require an oil pump as oil flow is ensured by the pressure difference between
delivery and suction. In addition to ensuring lubrication of ball bearings, oil injection dynamically seals the screw, thus
enabling the compression process.
- Water heat exchanger: Direct-expansion shell and tube heat exchanger for all models, it works as an evaporator
when the machine is in chiller mode and as a condenser when it is in heat pump mode.
- Air heat exchanger:
open fin; it works as an evaporator when the machine is in chiller mode and as a condenser when it is in heat pump
mode.
- Fan: High-efficiency axial type. Allows quiet operation of the system, even during adjustment.
- Expansion valve:
electronic device called a Driver that optimises its operation.
- 4-way valve: Allows the compressor delivery to be shunted towards the air heat exchanger for water chiller mode or
towards the water heat exchanger for water heater mode.
- VFD: This is an electronic power device that allows the continuous variation of the compressor rotation speed,
ensuring the modulation of the load provided with the utmost efficiency.

Description of the refrigeration cycle

The low-temperature refrigerant gas from the evaporator is drawn by the compressor through the electric motor, which
gets cooled by the refrigerant. It is subsequently compressed and during this process the refrigerant mixes with the oil
from the oil separator. The oil introduced is used to lubricate both the seal between the screw and the shell as well as
between the screw and the star.
The high-pressure oil-refrigerant mixture is introduced into the centrifuge-type high-efficiency oil separator, where the oil
is separated from the refrigerant. The oil accumulated on the bottom of the separator is forced by the pressure difference
back into the compressor while the oil-free refrigerant is sent to the condenser where the superheated refrigerant vapour
cools down and starts to condense and then the refrigerant subcools.
The heat taken from the fluid during the de-superheating, condensation and subcooling phase is transferred to the
outside air in chiller mode or to the water – which is thus heated - in heat pump mode.
The subcooled fluid flows through the high-efficiency filter dryer and then it reaches the expansion element (expansion
valve) through which a pressure drop takes place resulting in the vaporisation of part of the refrigerant liquid.
The result at this point is a low-pressure and low-temperature liquid-gas mixture entering the evaporator, where it takes
the heat required for vaporisation.
After the liquid-vapour refrigerant has been evenly distributed into the evaporator tubes, it exchanges heat with the water
to be cooled (in chiller mode), thus reducing the water temperature, or with the outside air (in heat pump mode) while it
gradually gets completely vaporised and then superheated.
Once it has reached the superheated-vapour state, the refrigerant leaves the evaporator and is once again taken into the
compressor to repeat the cycle.
In the heat pump unit, the water heat exchanger can be used to cool (chiller mode) or heat (heat pump mode) the water
that flows through it. To perform both functions (which obviously cannot be carried out simultaneously, and so the
desired operating mode needs to be selected), the water heat exchanger needs to be able to work as an evaporator
(chiller mode) or as a condenser (heat pump mode). This is accomplished thanks to a special valve (4-way valve)
designed to shunt the fluid on the oil separator outlet towards the water heat exchanger (in chiller mode) or towards the
water heat exchanger (in heat pump mode), making it work as a condenser and connecting the other heat exchanger
(water heat exchanger in chiller mode and air heat exchanger in heat pump mode) onto the compressor suction, making
it work as an evaporator. The difference in internal volume between an air heat exchanger and a water heat exchanger
makes it necessary for the circuit to feature an element (liquid receiver) designed to house the difference in liquid in both
operating modes.
Finned-pack type with internally micro-finned tubes, that expand directly on the high-efficiency
The standard machine has a an electronic expansion valve, which is controlled by an
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