McQuay SEASONCON ALP-037A, Руководство пользователя, Страница: 37 / 43

SERVICE
NOTE: Service on this equipment is to be performed by qualified refrigeration service personnel. Causes for repeated tripping
of safety controls must be investigated and corrected. CAUTION: Disconnect all power before doing any service inside the
unit.
FILTER-DRIERS
To change the filter-drier core(s), pump the unit down by
moving pumpdown switches PSI and PS2 to the “manual
pumpdown” position. Turn off all power to the unit and
install jumpers across the terminals shown in the table.
UNIT SIZE
JUMPER ACROSS
CIRCUIT NO.
T E R M I N A L S
THRU 1 114 to 116
ALP-046A T H R U 2 214 to 2 1 6
ALP-089A TH RU 1 1 1 4 t o 118
T H R U 159A 2 214
to 2 1 8
Turn power to the unit back on and restart the unit by
moving pumpdown switches PSI and PS2 to the “auto.
pumpdown” position. Close the manual liquid line shut-off
valve(s) and when evaporator pressure reaches 0 PSIG,
move the control stop switch
to the “off” position. This
will close the liquid line solenoid valve(s) and isolate the
short section of refrigerant piping containing the filter-
drier(s). Remove the cover plate from the filter-drier shell
and replace the core(s).
After core replacement, replace the cover plate. A leak
check around the flange of the filter-drier shell is recom-
mended after the cores have been changed.
LIQUID LINE SOLENOID VALVE
The liquid line solenoid valves, which are responsible for
automatic pumpdown during normal unit operation, do not
normally require any maintenance. They may, however,
require replacement of the solenoid coil or of the entire
The solenoid coil may be removed from the valve body
without opening the refrigerant piping by moving pump-
down switches PSI and PS2 to the “manual pumpdown”
valve assembly.
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
To replace the entire solenoid valve, the unit must be
for replacement. Be sure to replace the coil on its mounting
pumped down by use of the manual liquid line shut-off
stud before returning pumpdown switches PSI and PS2 to
valve.
the “auto. pumpdown” position.
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 super-
heat. (Superheat is the difference between refrigerant
temperature as it leaves the evaporator and the saturation
temperature corresponding to the evaporator pressure.)
Typically, superheat should run in the range of
to 15F.
On valves purchased through McQuay, the superheat setting
can be adjusted by removing a cap at the bottom of the
valve to expose the adjustment screw. Turn the screw clock-
wise (when viewed from the adjustment screw end) to
I N L E T
increase the superheat setting 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 using the manual liquid line shut-off
valve. If this 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
with the manual liquid line shut-off valves.
POWER ELEMENT
(CONTAINS DIAPHRAGM)
O U T L E T
. - S P R I N G
S
C R E W
PAGE 37