Parker SEHI Series Operating, Installation And Servicing Instructions

SEHI (SEI & SEH)
Step Motor Expansion Valves
INSTALLATION AND SERVICING INSTRUCTIONS
SD-243 / 52025
OPERATION
The SEI and SEH series valves are 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 advantages of step motors in
valve applications are high resolution, repeatability and reliability
with low hysteresis. Feedback loops are not required, simplifying
controller design and circuitry.
The step motor used in the SEI and SEH valves 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. Various Sporlan and third
party controllers are available for use with the valve. 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.
INSTALLATION
The SE series valves are electronically controlled Step Motor
Expansion Valves, and are installed before the distributor and
evaporator just as one would install a Thermostatic Expansion
Valve. The valves are directional, and the inlet is clearly marked.
Location should be planned to provide serviceability and to
allow controller installation within a cable length of forty feet.
The valve may be installed in the refrigerated space and may be
mounted in any position except with the motor housing below
horizontal. Cable routing should avoid any sharp edges or other
sources of potential physical damage such as defrost heaters
and fan blades. For neatness and protection, the cable may
be fastened to the suction or liquid lines with nylon wire ties.
The valves have copper connections and any suitable solder or
brazing alloy may be used to install the valve. There is no need
to disassemble the valve for installation, however, the torch
flame should be directed away from the motor housing and
cable. Care must be taken to assure that the cable is not damaged
either directly from the flame, or indirectly from contact with hot
piping. The valve is shipped in the open position to prevent heat
being conducted into the motor, but it is strongly suggested that
the valve body be wrapped with a wet cloth during the soldering
operation. Inlet strainers are supplied optionally with ODF style
valves, and if used, should be oriented in the proper direction as
shown on the strainer package. The valve should be completely
installed and reassembled before connecting to the controller
and applying power. The wiring is color-coded and the controller
manufacturer should be consulted for the proper attachment to
the controller.
FIELD SERVICING INSTRUCTIONS
SEI & SEH ONLY
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 SEI/SEH 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 to
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 as shown