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 50 page image

50Refrigerant Charge — Amount of refrigerant charge islisted on unit nameplate. Refer to Carrier GTAC II; Module 5;Charging, Recovery, Recycling, and Reclamation section forcharging methods and procedures. Unit panels must be in placewhen unit is operating during charging procedure.Puron® (R-410A) refrigerant cylinders contain a dip tubewhich allows liquid refrigerant to flow from the cylinder in anupright position. Charge units with cylinder in the uprightposition and a commercial type metering device in the mani-fold hose.NOTE: Do not use recycled refrigerant as it may containcontaminants.NO CHARGE — Use standard evacuating techniques. Afterevacuating system, weigh in the specified amount of refriger-ant (refer to unit nameplate).LOW CHARGE COOLING — Using cooling charging chart(see Fig. 37-39), add or remove refrigerant until conditions ofthe chart are met. An accurate pressure gage and temperature-sensing device are required. Charging is accomplished byensuring the proper amount of liquid subcooling. Measureliquid line pressure at the liquid line service valve using pressuregage. Connect temperature sensing device to the liquid line nearthe liquid line service valve and insulate it so that outdoor ambi-ent temperature does not affect reading.TO USE THE COOLING CHARGING CHART — Use theabove temperature and pressure readings, and find the intersec-tion point on the cooling charging chart. If intersection point onchart is above line, add refrigerant. If intersection point onchart is below line, carefully recover some of the charge. Re-check suction pressure as charge is adjusted.NOTE: Indoor-air cfm must be within normal operating rangeof unit. All outdoor fans must be operating.The TXV (thermostatic expansion valve) is set to maintainbetween 10 and 15 degrees of superheat at the compressors.The valves are factory set and cannot be adjusted. Do not use aTXV designed for use with R-22 refrigerant.PURON REFRIGERANT — Puron refrigerant operates at 50to 70 percent higher pressures than R-22. Be sure that servicingequipment and replacement components are designed to oper-ate with Puron refrigerant. Do not mix with components thathave been used with other refrigerants. Puron refrigerant, aswith other HFCs, is only compatible with POE oils.Recovery cylinder service pressure rating must be 400 psig.Puron systems should be charged with liquid refrigerant. Use acommercial-type metering device in the manifold hose. Mani-fold sets should be 750 psig high-side and 200 psig low-sidewith 520 psig low-side retard. Use hoses with 750 psig servicepressure rating. Leak detectors should be designed to detectHFC refrigerant.Gas Valve AdjustmentNATURAL GAS — The gas valve opens and closes in re-sponse to the thermostat or limit control.When power is supplied to valve terminals W2 (High Fire)and C1, the main valve opens to its preset position.The regular factory setting is stamped on the valve body.The setting is 3.00 in. wg for vertical supply/discharge units.The setting is 2.95 in. wg for horizontal supply/discharge units.To adjust regulator:1. Set unit at setting for no call for heat.2. Turn main gas valve to OFF position.3. Remove 1/8-in. pipe plug from manifold or gas valvepressure tap connection. Install a suitable pressure-measuring device.This system uses Puron refrigerant which has higherpressures than R-22 and other refrigerants. No other refrig-erant may be used in this system. Gage set, hoses, andrecovery system must be designed to handle Puron refrig-erant. If unsure about equipment, consult the equipmentmanufacturer. Fig. 38 — Charging Chart — 48PG24Fig. 39 — Charging Chart — 48PG28Fig. 37 — Charging Chart — 48PG20