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11 -MAJOR SYSTEM COMPONENTS AND OPERATION DATA
11.2.1 - Evaporator
30XB(E/P)ZE chillers use a flooded multi-tube evaporator. The water
circulates in the tubes and the refrigerant is on the outside in the
shell. One vessel is used to serve both refrigerant circuits. There
is a centre tube sheet which separates the two refrigerant circuits.
The tubes are 3/4" diameter copper with an enhanced surface
inside and out. There is just one water circuit, and depending on
the size of the chiller, there may be one, two or three water passes.
The units have three refrigerant circuits with two evaporators
connected in series on the heat transfer fluid.
The maximuum standard operating pressures are 2100 kPa
relative for the refrigerant side and 1000 kPa relative for the water-
side.
The evaporator has a thermal insulation of 19 mm thick
polyurethane foam, an aluminium sheet (option) and is equipped
with a water drain and purge.
The water connection of the heat exchanger is a Victaulic
connection. As an option the evaporator is available with frost
protection (evaporator frost protection option).
The products that may be added for thermal insulation of the
containers during the water piping connection procedure must be
chemically neutral in relation to the materials and coatings to which
they are applied. This is also the case for the products originally
supplied by Carrier.
11.2.2 - Oil separator
In these units, the oil separator is a pressure vessel that is mounted
under the outside vertical condenser coils. Dis-charge gas at the
compressor outlet is directed towards the bottom of the oil separator
ring and most of the oil separates from the gas by strong
deceleration and by gravity. The gas then flows through a wire
mesh screen where the remaining oil is separated by coalescence
and flows to the bottom of the ring. The gas is now free from oil
and leaves the ring at the top towards the condenser.
The oil separator is equipped with a trace heater regulated by the
control.
11.2.3 - Economiser function
The economiser function includes a liquid line valve, a filter drier,
two EXVs, a plate heat exchanger as well as protection devices
(fuse or valve).
At the condenser outlet a part of the liquid is expanded via the
secondary EXV in one of the heat exchanger circuits and then
returns as gas at the compressor economiser. This expansion
permits increase of the liquid sub-cooling of the rest of the flow that
penetrates the evaporator via the principal EXV. This permits
increasing the cooling capacity of the system as well as its
efficiency.
11.3 - High pressure safety buckle (SRMCR)
11.3.1 - General description
The device is equipped with a high pressure safety loop, also known
as safety related measurement control and regulation system
(SRMCR), consisting of
- 2 PZHH type high pressure switches (HPS) with manual reset
located at the outlet of each compressor
- A control relay on the compressor board.
- 2 compressor main contactors
See the wiring diagram and bill of material of the unit for details of
identification and references.
This safety loop is designed according to EN 61508 for:
SIL level (Safety Integrity): 2.
Demand mode: high and low.
Mission Time: 20 years.
Periodic test: The safety loop operation must be tested at least once
a year to maintain its integrity.
11.3.2 - Function description and reset
Diagram below describes the description of operation: refer to the
machine documentation to obtain the detailed wiring diagram
The HPS switches are wired in series to the control relays of the A_C
board which controls the KM and KM-D main contactors. Both switches
are closed during continuous operation of the compressor. When one
of the HPS switches opens, the control relay interrupts the supply
voltage of the KM-and KM-D contactor coil: the main contactor opens,
which causes the compressor to lose power and stop .
The operation of this safety loop is electromechanical: it is not based
on software or an electronic component.
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