Daikin WGZ030DW Installation, Operation And Maintenance Manual page 70

DANGER
LOCKOUT/TAGOUT all power sources prior to servicing the unit.
Disconnect all power before performing any service inside the unit or
serious personal injury or death can occur. Service on this equipment is
to be performed only by qualified refrigeration personnel. Causes for
repeated tripping of equipment protection controls must be investigated
and corrected. Gas condition can cause serious injury or death. Close gas
connections/valves before servicing equipment.
NOTE: Anyone servicing this equipment must comply with
all applicable industry related published standards
and local, state and federal, statutes, regulations
and codes concerning refrigerant reclamation and
venting.
Filter-Driers
To change the filter-drier, pump the unit down (with the
compressor running) by closing the manual liquid line shutoff
valve(s). The unit will start pumping down until it reaches the
low-pressure cutoff setting of 85 psi (585 kPa).
Close the discharge valve. Remove the refrigerant in the liquid
line with a recovery unit to EPA required pressure. Remove
and replace the filter-drier(s). Evacuate the lines through the
liquid line manual shutoff valve(s) to remove noncondensables
that may have entered during filter replacement. A leak check
is recommended before returning the unit to operation.
Liquid Line Solenoid Valve
The liquid line solenoid valve(s), which are responsible for
automatic pumpdown during normal unit operation, do not
normally require any maintenance. However, in the event of
failure they can require replacement of the solenoid coil or of
the entire valve assembly.
The solenoid coil can be removed from the valve body without
opening the refrigerant piping by moving pumpdown switch
PS1 or PS2 to the "manual" position.
The coil can then be removed from the valve body by simply
removing a nut or snap-ring located at the top of the coil. The
coil can then be slipped off its mounting stud for replacement.
Be sure to replace the coil on its mounting stud before
returning the pumpdown switch to the "auto pumpdown"
position.
To replace the entire solenoid valve, follow the steps for
changing a filter-drier.
Thermostatic Expansion Valve
The expansion valve is responsible for allowing the proper
amount of refrigerant to enter the evaporator regardless of
cooling load. It does this by maintaining a constant superheat
(Superheat is the difference between refrigerant temperature
as it leaves the evaporator and the saturation temperature
corresponding to the evaporator pressure). All WGZ chillers
are factory set for between 8°F and 12°F (4.4°C to 6.7°C)
superheat at full load.
To increase the superheat setting of the valve, remove the cap
at the bottom of the valve to expose the adjustment screw.
IOM 1322-1 • WATER-COOLED SCROLL COMPRESSOR
Turn the screw clockwise (when viewed from the adjustment
screw end) to increase the superheat and counterclockwise to
reduce superheat. Allow time for system rebalance after each
superheat adjustment.
The expansion valve, like the solenoid valve, should not
normally require replacement, but if it does, the unit must be
pumped down by following the steps involved when changing a
filter-drier.
If the problem can be traced to the power element only, it can
be unscrewed from the valve body without removing the valve,
but only after pumping the unit down.
Figure 37: Thermostatic Expansion Valve
Adjustment of expansion valve should only be performed by a qualified
service technician. Failure to do so can result in improper unit operation..
NOTE: Superheat will vary with compressor unloading, but
should be between 8°F and 12°F (4.4°C and 6.7°C)
with stable operation.
Water-cooled Condenser
The condenser is of the shell-and-tube type with water
flowing through the tubes and refrigerant in the shell. Integral
subcoolers are incorporated on all units. All condensers are
equipped with 500 psig (3450 kPa) relief valves. Normal tube
cleaning procedures can be followed.
Evaporator
The evaporators are sealed, brazed-stainless steel plate unit or
DX shell-and-tube. Normally no service work is required on the
evaporator.
70
Unit Maintenance
CAUTION
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