Operating instructions

TM 11574A-OI
3-29
NOTE
Carefully listen to the valve. During reset, the valve will make a ratcheting noise that may
be heard or felt as it is attempting to close. If this can be heard or felt, it indicates that the
controller and drive module are attempting to close the valve, and may serve as a quick
indication that the drive module is in working order.
5
During the first few minutes of unit operation, compressor reliability enhancement
logic (CREL) may be in effect. This places the valve at a 21% staging position and is
sufficient to drive the temperature of the supply probe down several degrees during
this interval.
6
After the CREL time-out has been met, the valve will start responding to the control
logic and open or close relative to the demand. Scrutinize the unit operation for a
few minutes. While in pull down, the unit will open the SMV to a maximum discharge
pressure of 325 psig in high ambient conditions, or as much as the current setting
and control logic will allow. The current level should be high. A lower discharge
pressure will be seen in lower ambient temperatures. Once the unit has reached set
point, the SMV will go into control mode. Both the discharge/suction pressures, and
current draw will go significantly lower. Once below set point, the suction pressure
should go into a vacuum within several minutes. Should the operation differ as
mentioned, the SMV, controller, or wiring, may be faulty.
7
Check for correct wire location at the stepper motor plug and the environmental
connector (EC). Make sure that the wires terminate in accordance with the wire
markings (addresses).
8
Attach a manifold gauge set (refer to Manifold gauge set paragraph 3-10b(2)). If the
unit is operating in the perishable mode, proceed to step 9. If the unit is operating in
the frozen mode, proceed to step 10
.
9
Perishable operation: If the operation of the unit is in question, place the set point to
approximately 11 F (6 C) less than the current box temperature, so the unit goes into
pull down. Run the unit for approximately one minute. Record readings on gauges
and current draw. The current draw and pressures should go up. Place set point 0.9
F (0.5 C) above current box temperature to fully modulate valve, and run for
approximately one minute.
NOTE
The unit may shut off for a short time. Wait until the unit self starts and sufficient time has
elapsed to cause the valve to fully modulate.
Record new gauge readings and current draw. The suction pressure should go into a vacuum
and the current draw should have gone down. If little or no change to the suction pressure or
current draw occurs, this is an indication of a malfunctioning SMV.
10
Frozen operation: In frozen mode the valve tends to stay open as much as possible.
Again, this is dependent upon current limit setting and control logic. Turn the unit
OFF and ON, as in the perishable mode, and watch the gauges. The valve will run at
21% open if CREL logic is active, and will open to maximum allowable after this.
Depending on ambient conditions, there should be an increase in suction pressure
and current draw as the valve opens. However, at times, this may be difficult to fully
determine.
11
If the unit still does not operate properly, stop unit and proceed to the following step
to check out the SMV system.