Carrier SINGLE PACKAGE ROOFTOP UNITS 48PG20-28 Installation And Service Instructions Manual

Also see for 48PG20---28: User's information manual User's information manual Controls, start-up, operation, service and troubleshooting instructions

Carrier SINGLE PACKAGE ROOFTOP UNITS 48PG20-28 Installation And Service Instructions Manual Manual pdf 18 page image

18PRE-START-UPProceed as follows to inspect and prepare the unit for initialstart-up:1. Remove all access panels.2. Read and follow instructions on all WARNING, CAU-TION, and INFORMATION labels attached to, orshipped with, the unit.3. Make the following inspections:a. Inspect for shipping and handling damages such asbroken lines, loose parts, or disconnected wires, etc.b. Inspect for oil at all refrigerant tubing connectionsand on unit base. Detecting oil generally indicates arefrigerant leak. Leak-test all refrigerant tubing con-nections using an electronic leak detector, halidetorch, or liquid-soap solution.c. Inspect all field-wiring and factory-wiring connec-tions. Be sure that connections are completed andtight.d. Inspect coil fins. If damaged during shipping andhandling, carefully straighten the fins with a fincomb.4. Verify the following conditions:a. Make sure that condenser fan blade is correctlypositioned in the fan orifice. See Condenser-FanAdjustment section on page 49 for more details.b. Make sure that air filter(s) is in place.c. Make sure that condensate drain trap is filled withwater to ensure proper drainage.d. Make sure that all tools and miscellaneous loose partshave been removed.START-UPUse the following information and Start-Up Checklist onpage CL-1 to check out unit PRIOR to start-up.Unit Preparation — Check that unit has been installed inaccordance with these installation instructions and all applica-ble codes.Compressor Mounting — Compressors are internallyspring mounted. Do not loosen or remove compressor hold-down bolts.Refrigerant Service Ports — Each independent re-frigerant system has a total of 3 Schrader-type service gageports per circuit. One port is located on the suction line, one onthe compressor discharge line, and one on the liquid line. Besure that caps on the ports are tight.Crankcase Heater(s) — Crankcase heaters are ener-gized as long as there is power to the unit and the compressor isnot operating.Compressor Rotation — On 3-phase units, it is impor-tant to be certain the scroll compressor is rotating in the properdirection. To determine whether or not compressor is rotatingin the proper direction:1. Connect service gages to suction and discharge pressurefittings.2. Energize the compressor.3. The suction pressure should drop and the discharge pres-sure should rise, as is normal on any start-up.If the suction pressure does not drop and the discharge pres-sure does not rise to normal levels:1. Note that the evaporator fan is probably also rotating inthe wrong direction.2. Turn off power to the unit and install lockout tag.3. Reverse any two of the unit power leads.4. Turn on power to the unit.The suction and discharge pressure levels should now moveto their normal start-up levels.NOTE: When the compressor is rotating in the wrong direc-tion, the unit makes an elevated level of noise and does notprovide heating or cooling.Internal Wiring — Check all electrical connections inunit control boxes; tighten as required.Subcooler Heat Exchanger (SHX) — The subcool-er heat exchanger adds approximately 10 to 15° F of sub-cooling to the system. Check all valves and TXV (thermostaticexpansion valve).Evaporator Fan — Fan belt and variable pulleys arefactory-installed. See Tables 5-23 for fan performance data. Besure that fans rotate in the proper direction. See Table 24 for airquantity limits. See Table 25 for evaporator fan motor specifi-cations. See Table 26 for accessory/FIOP static pressure. SeeTable 27 for fan rpm at various motor pulley settings. To alterfan performance, see Evaporator Fan Performance Adjustmentsection on page 48.Failure to observe the following warnings could result inserious personal injury.1. Follow recognized safety practices and wear protectivegoggles when checking or the servicing refrigerantsystem.2. Do not operate the compressor or provide any electricpower to the unit unless the compressor terminal coveris in place and secured.3. Do not remove the compressor terminal cover until allelectrical sources are disconnected.4. Relieve all pressure from the system before touching ordisturbing anything inside the compressor terminal boxif refrigerant leak is suspected around the compressorterminals.5. Never attempt to repair a soldered connection while therefrigerant system is under pressure.6. Do not use torch to remove any component. The sys-tem contains oil and refrigerant under pressure. Toremove a component, wear protective goggles and pro-ceed as follows:a. Shut off gas and then electrical power to the unit.Install lockout tag.b. Relieve all pressure from the system using bothhigh-pressure and low-pressure ports.c. Cut the component connection tubing with a tubingcutter, and remove the component from the unit.d. Carefully unsweat the remaining tubing stubs whennecessary. Oil can ignite when exposed to torchflame.IMPORTANT: Unit power must be on for 24 hours priorto start-up. Otherwise, damage to compressor mayresult.Compressor damage will occur if rotation is not immedi-ately corrected.