Carrier GR-45 Operation And Service

Contents

Carrier GR-45 Operation And Service Manual pdf 35 page image

T-295 4-2SERVICEPORTVALVE CAPVALVESTEMTO DISCHARGE ORFROM SUCTIONLINEPORT TOCOMPRESSORService ValveFrontseated(clockwise)Service ValveBackseated(counterclockwise)Figure 4-2.Suction or Discharge Service Valve4.4 INSTALLING MANIFOLD GAUGE SETA manifold gauge set (Figure 4-3) can be used todetermine system operating pressures, add charge,equalize or evacuate the system.Hand Valve(Backseated) Hand Valve(Frontseated)SuctionPressureGaugeDischargePressureGaugeA BCA. Connection to Low Side of SystemB. Connection to High Side of SystemC. Connection to Vacuum Pump, RefrigerantCylinder, Oil Container or Evacuation LineFigure 4-3. Manifold Gauge SetWhen the suction pressure hand valve is frontseated(turned all the way in), the suction (low) pressure can beread. When the discharge pressure hand valve isfrontseated, discharge (high) pressure can be read.When both valves are open (turned counterclockwise),high pressure vapor will flow into the low side. Whenonly the low pressure valve is open, the system can becharged or evacuated. To install a manifold gauge set,do the following (refer to Figure 4-4, Figure 4-5 orFigure 4-6 as applicable).a. Remove the service valve stem caps and backseat(counterclockwise) both valves. Remove the serviceport caps.b. Connect the discharge side hose tightly to the servicevalve port.c. Connect the suction side hose loosely to the other ser-vice valve port.d. Loosen charging (center) hose at dummy fitting ofmanifold set.e. Frontseat (clockwise) both manifold gauge handvalves.f. Turn the service valve connected to the dischargegauge port toward frontseat (clockwise) approxi-mately 1/4 to 1/2 turn.g. Slowly turn the manifold discharge hand valve to-ward backseat (counterclockwise) approximatelyone turn.h. Tighten charging hose onto dummy fitting.i. Slowly turn the manifold suction hand valve towardbackseat (counter--clockwise) to remove air fromline.j. Tighten suction hose at the service valve port.k. Frontseat (close) both manifold hand valves.l. Turn the service valve connected to the suction gaugeport toward frontseat (clockwise) approximately 1/4to 1/2 turn.4.5 PUMPING THE SYSTEM DOWN OR REMOV-ING THE REFRIGERANT CHARGENOTETo avoid damage to the earth’s ozone layer, usea refrigerant recovery system whenever remov-ing refrigerant.4.5.1 System Pump Down For Low Side RepairTo service or replace the filter--drier, thermostaticexpansion valve, suction line or evaporator coils, pumpthe refrigerant to the condenser and receiver as follows:a. Install manifold gauge set. Refer to Figure 4-4b. Frontseat the filter--drier inlet service valve by turn-ing clockwise. Disconnect suction pressure transduc-er and install a jumper on the compressor mountedlow pressure switch.c. Start the system and run in cooling. Stop the unitwhen suction reaches 10 ”/hg (25.4 cm/hg) vacuum.d. Frontseat compressor suction service valve to trap re-frigerant in the high side of the system between thecompressor suction service valve and the filter--drierinlet valve. Wait 5 minutes to verify that system re-mains in a vacuum. If system pressure rises abovevacuum, open compressor suction service valve andrepeat steps c and d until system remains in vacuum.e. Service or replace necessary components.f. Leak check connections and replace filter--drier. Re-fer to paragraph 4.6.g. Using refrigerant hoses designed for vacuum service,evacuate and dehydrate the low side of the system byconnecting a vacuum pump to center connection ofmanifold gauge set. Evacuate system to 500 microns.Close off pump valve, isolate vacuum gauge and stoppump. Wait 5 minutes to verify that vacuum holds.h. Recharge low side to 20 to 30 psig (1.36 to 2.04 bar)by admitting vapor from the refrigerant cylinder.