CRR-20 & CRR-40, September 1999
Refrigeration Maintenance and Service Operations
Evaporator Pressure Regulator (KVQ Valve)
6-13
10. Close the refrigerant tank hand valve when the correct
amount (by weight) of refrigerant has been added or if the
system will take no more liquid.
The unit is now ready to have the Evacuation Station
removed (described in the following steps, “Evacuation
Station Removal”). See following, “Final Charging
Procedure for Partially Charged Units” to complete charg-
ing procedure.
Evacuation Station Removal
1.
Back seat the discharge service valve.
2.
Close the refrigerant tank hand valve.
3.
Operate the unit in cool mode.
4.
Open the hand valve at the gauge manifold and read suc-
tion pressure.
5.
Front seat the suction service valve and pump down the
system to 21 to 35 kPa, 0.21 to 0.35 bar, 3 to 5 psig.
6.
Back seat the suction service valve.
7.
Remove the hose from the discharge service valve.
8.
Install a gauge manifold set.
• If the unit is fully charged, perform a functional check
out.
• If the unit has a partial charge, complete the charging
process as described below.
Final Charging Procedure for Partially Charged Units
1.
Connect the gauge manifold to the suction line and dis-
charge line service ports. Be sure to purge the air from
the lines (see “Gauge Manifold Set Attachment and
Purging” in the Refrigeration Maintenance chapter of this
manual).
2.
Back seat and crack the discharge service valve.
3.
Connect a refrigerant tank to the gauge manifold service
line.
4.
Set the refrigerant tank for liquid charging. Open the
refrigerant tank hand valve.
5.
Start and operate the unit in the COOL mode.
6.
Read the suction pressure and slowly open the gauge man-
ifold low pressure hand valve to permit suction pressure to
increase approximately 170 kPa, 1.7 bar, 25 psig. This
will meter liquid refrigerant slowly into the low side.
7.
Add refrigerant until the receiver tank balls float at the top
of the sight glass.
8.
Close the hand valve on the refrigerant tank.
9.
Operate the unit on COOL for 10 minutes and recheck
refrigerant charge.
10. Remove the gauge manifold set.
11. Cap all service ports and valve stems.
CAUTION: If the controller temperature setpoint was
lowered to force COOL operation, be sure to return
the controller to the setpoint indicated on the ship-
ping manifest.
Evaporator Pressure Regulator (KVQ) Valve
The evaporator pressure regulator valve is used to control the
flow of refrigerant to the compressor when the unit is operat-
ing in the Modulation mode. As the supply air temperature
approaches setpoint, the controller sends a voltage pulse to a
heater in the valve. The heater warms a pressure reservoir in
the valve actuator. As the pressure in the fluid reservoir
increases, a pressure pin overcomes the spring tension in the
bellows, closing the valve plate a precise amount. This throt-
tles the suction gas returning to the compressor and reduces
cooling capacity. As the frequency of the voltage pulse is
increased, the pressure pin closes the valve plate an additional
amount. Due to valve design, the flow of refrigerant gas exerts
no opening or closing forces on the valve plate, allowing very
precise operation.
NOTE: If the electrical circuit to the heating element
fails, the valve moves to the full open position.
Service of the evaporator pressure regulator valve
includes replacement of the actuator assembly or replacement
of the valve body.
Tools Required:
• Digital Multimeter (P/N 204-615)
• Actuator Assembly
• Adjustable Wrench
• Torque Wrench
Содержание CRR-20
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