ClimaCool UGW Manual - Manual (Page 51)

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Refrigeration System Re-Processing and Charging
Operation
This valve is a step motor operated electric expansion
valves . Step motors are designed to provide discrete
segments of angular motion, or rotation, in response to an
electronically generated signal .
The step motor used in this valve is a 12-volt DC,
two-phase, bi-polar, permanent magnet rotor type . Motor
rotation is converted to linear motion by the use of a lead
screw and threaded drive coupling . Forward motion of the
motor extends the drive coupling and pin, which moves the
valve to the closed position . Backward rotation of the motor
retracts the drive coupling and pin modulating the valve in
the opening direction . Full forward or backward travel, while
the valve is assembled, is limited by the valve seat in the
closed position or by the controller in the open direction . A
slight clicking sound may be heard when overdriving closed
and does no harm to the valve or drive mechanism .
The valve will operate only when connected to a properly
designed controller . The controller must supply the
necessary square wave step signal at 12 volts DC and
200 PPS, or a properly configured current limited signal
up to 400 PPS, for the valve to control properly . Control
algorithms for the valve include a initialization sequence
that will first over-drive the valve in the closing direction.
This is to assure that the valve is completely shut and to
establish the “zero” open position . The controller then
keeps track of the valve’s position for normal operation .
During this initialization phase, a light clicking sound may
be heard, which will serve as proof of the valve’s operation
and closure .
All valves are tight seating and uniquely characterized by pin
and port combinations for exceptional control of refrigerant
flow. The seats require no service and are not replaceable.
The motor may be easily replaced without removing the
valve body from the system .
Field Service Instructions
The following steps are necessary for the proper
disassembly, inspection, cleaning and reassembly of all
valves (whether in or out of the refrigerant piping).
1. Before disassembling the valve, be sure the refrigerant
pressure in the system has been reduced to
a safe level (0 psig).
2. Disconnect the line voltage to the valve controller .
3. Refer to the exploded view of the valve for the
remaining instructions . Using the appropriate wrenches
or a vice to properly support the valve body, remove the
motor assembly from the valve body by loosening the
lock nut . To prevent permanent damage to the motor,
DO NOT attempt disassemble the motor housing .
CAUTION: Regardless of whether the valve is in the system
or in a vise, care must be taken to prevent distorting the
valve parts when tightening.
4. The motor assembly may be removed for inspection
and cleaning .
5. If the motor fails to operate properly, check the resistance
of each motor phase . Resistance between the black and
white leads or between the red and green leads should
be 75 ± 10%. Differences of more than 10% between phases
indicate a defective motor . Resistance between black
and red, or any lead and housing should be infinite, any
resistance reading will indicate a shorted winding and the
motor will need to be replaced .
6. If you have access to a SMA test instrument, operation of
the valve may be proven . Connect the motor leads to the
proper color-coded connector on the SMA . Set the rate
to 200 PPS and toggle in the “OPEN” direction . The white
driver/piston should retract into the driver guide/adaptor .
After approximately 30 seconds, the driver should be fully
retracted and a light clicking or “ratcheting” sound may be
heard, this is normal to the valves and proves operation of
the motor . If the SMA is toggled in the “CLOSE” position,
after approximately 30 seconds the white polyester
driver/piston should disengage the lead screw, and can be
removed . Inspect the driver/piston for damage . To replace
the driver, toggle the SMA to the “OPEN” position and
carefully engage the driver to the lead screw .
CAUTION: Whenever the motor is powered while not in
place on the valve, the driver must be fully retracted into
the guide before the valve is reassembled. Failure to do this
will permanently damage the valve.
7. If the motor responds to step 6 above, the valve body itself
should be checked for obstruction . Check for contaminants
in the port or strainer, if used .
8. If the valve body and strainer are clear and the motor
operates as in step 6 above, the valve is considered
operational and the problem lies in the controller or
power supply .