Carrier 38MGR Series Service Manual

Carrier 38MGR Series Service Manual Manual pdf 25 page image

38MGR-04SM Specifications subject to change without notice. 25SYSTEM EVACUATION AND CHARGINGRefrigerant tubes and indoor coil should be evacuated using therecommended deep vacuum method of 500 microns. The alternatetriple evacuation method may be used if the following procedure isfollowed. Always break a vacuum with dry nitrogen.NOTE: All units (except the 18,000 BTU model) have aMaster Suction and Liquid Line Service Valve.System Vacuum and ChargeUsing Vacuum Pump1. Completely tighten the flare nuts (A, B, C, D, E). Fully open allcircuits service valves. Connect the manifold gage charge hose tothe charge port of the low side Master service valve to evacuate allcircuits at the same time (see Fig. 23).2. Connect charge hose to vacuum pump.3. Fully open the low side of manifold gage (see Fig. 24).4. Start vacuum pump5. Evacuate using the triple evacuation method.6. After evacuation is complete, fully close the low side of manifoldgage and stop operation of vacuum pump.7. The factory charge contained in the outdoor unit is good for upto 25ft. (8 m) of line length. For refrigerant lines longer than25ft. (8 m), add refrigerant as specified in “Additional ChargeTable Per Zone” on page 24.8. Disconnect charge hose from charge connection of the low sideservice valve.9. Securely tighten caps of service valves.Fig. 23 — Service ValveFig. 24 — ManifoldDeep Vacuum MethodThe deep vacuum method requires a vacuum pump capable of pullinga vacuum of 500 microns and a vacuum gage capable of accuratelymeasuring this vacuum depth. The deep vacuum method is the mostpositive way of assuring a system is free of air and liquid water (seeFig. 25).Fig. 25 — Deep Vacuum GraphTriple Evacuation MethodThe triple evacuation method should be used. Refer to Fig. 26 andproceed as follows:1. Pump the system down to 1500 microns and allow the pump tocontinue operating for an additional 15 minutes.2. Close the service valves and shut off the vacuum pump.3. Connect a dry nitrogen cylinder and regulator to the system andbreak vacuum until the system reaches 2 psig.4. Close the service valve and allow the system to stand for 1 hour.During this time, the dry nitrogen can diffuse throughout the systemabsorbing moisture.5. Pump the system down to 1000 microns.6. Break the vacuum with dry nitrogen (2 psig).7. Pump the system down to 500 microns.8. Perform the hold test for 30 minutes.Fig. 26 — Triple Evacuation MethodFinal Tubing CheckIMPORTANT: Check to be certain factory tubing on bothindoor and outdoor unit has not shifted during shipment.Ensure tubes are not rubbing against each other or any sheetmetal. Pay close attention to feeder tubes, making sure wireties on feeder tubes are secure and tight.UNIT DAMAGE HAZARDFailure to follow this caution may result in equipment damageor improper operation.Never use the system compressor as a vacuum pump.CAUTIONOutdoor Unit Indoor UnitRefrigerantService ValveLow SideHigh SideABCDManifold Gage500 micronsLow side valve High side valveCharge hose Charge hoseVacuum pumpLow side valve500MINUTES0 1 2 3 4 5 6 710001500LEAK INSYSTEMVACUUM TIGHTTOO WETTIGHTDRY SYSTEM2000MICRONS250030003500400045005000CHECK FOR TIGHT, DRY SYSTEM(IF IT HOLDS DEEP VACUUM)EVACUATE TO 1500 MICRONSEVACUATE TO 500 MICRONS MINIMUM (HOLD FOR 30 MINUTES)RELEASE CHARGE INTO SYSTEM BY OPENING VALVES COMPLETELYBREAK VACUUM WITH DRY NITROGEN TO 2 PSIGEVACUATE TO 1000 MICRONSBREAK VACUUM WITH DRY NITROGEN TO 2 PSIG