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9.7.5 - Corrosion allowances
Gas side: 0 mm
Heat exchange fluid side: 1 mm for tubular plates in lightly
alloyed steels, 0 mm for stainless steel plates or plates with
copper-nickel or stainless steel protection.
9.7.6 - evaporator
30XAV-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 with two water passes (one
pass when 100C is selected).
The evaporator has been tested and stamped in accordance
with the applicable pressure code. The maximum maximum
standard relative operating pressure is 2100 kPa for
refrigerant side and 1000 kPa for water side. These pressures
can be different depending on the regulation and the code
applied.
The evaporator has a thermal insulation of 19 mm thick
polyurethane foam, aluminium cladding may be fitted as
an option and is equipped with a water vent and purge.
The water connection of the heat exchanger is a Victaulic
connection. As an option the evaporator is available with
freeze protection (evaporator freeze 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.
9.7.7 - oil separator
In these units, the oil separator is a pressure vessel that is
mounted under the outside vertical condenser coils.
Discharge gas at the compressor outlet is directed towards
the bottom of the oil separator 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 vessel. The gas is now free from oil and leaves the
vessel at the top towards the condenser.
The oil separator is equipped with a trace heater regulated
by the unit controls.
9.7.8 - assembly function
The assembly function includes a liquid line valve, a filter
drier, two EXVs, a plate heat exchanger as well as
protection devices (seal or valve).
At the condenser outlet a part of the liquid is expanded via
the secondary EXV in one of the heat exchanger port and
then returns as gas at the compressor economiser. This
expansion increases the sub-cooling of the bulk of the
liquid refrigerant which then flows into the evaporator via
the main EXV. This increases both the capacity and
efficiency of the system.
9.8 - high-pressure safety switch
30XAV-ZE units are equipped with high-pressure safety
switches.
In accordance with the applicable code the high-pressure
switches with manual reset, called PZH (former DBK), may
be backed up by high-pressure switches that require
resetting with a tool. The high-pressure switches that
require resetting with a tool are called PZHH (former
SDBK). If a PZHH cuts out, the corresponding PZH in
the same compressor is faulty and must be replaced. The
PZHH must be reset with a blunt tool with a diameter of
less than 6 mm. Insert this tool into the opening on the
pressure switch and push the reset.
These pressure switches are located at the discharge of each
compressor.
9.9 - condensers
30XAV-ZE coils are all-aluminium micro-channel
condensers.
9.10 - fans
The fans are axial Flying Bird fans equipped with rotating
shroud and made of composite recyclable material. Each
motor is fixed with transverse supports. The motors are
three-phase, with permanently lubricated bearings and
insulation class F (level IP55).
All fans in the same refrigerant circuit are controlled by
one or two variable speed drives. Therefore, they operate
together at the same rotational speed. The rotational speed
at full load or partial load of each circuit is controlled by
an algorithm that continuously optimises the condensing
temperature to obtain the best energy efficiency (EER)
whatever the operating conditions.
9.10.1 - fan motor electrical protection
The motors of a same circuit are electrically protected by
the variable frequency drive in case of short-circuit, locked
rotor or general overload. Each variable frequency drive
follows a variable current characteristic, based on the
frequency from 5 to 50 Hz and the number of fans
controlled.
In case of fan failure (in open circuit), the variable
frequency drive will automatically detect the problem and
send an alert to the user interface. Refer to the 30XAV-ZE
control manual for the list of alarms specific to this option.
