Carrier 48/50PD05 manual Verify Sensor Performance, Economizer Operation During Power Failure

48/50PD

C08570

Fig. 33 - Condenser-Fan Adjustment

Verify Sensor Performance

Verify that thermistor, transducer, and switch inputs are reading correctly. These values can be accessed through the Scrolling Marquee display in the Temperatures, Pressures, and Inputs menus. Some values will depend on configuration choices. Refer to the Control Set Up Checklist completed for the specific unit installation and to the configuration tables in Appendix A.

Economizer Operation During Power Failure

Dampers have a spring return. In event of power failure, dampers will return to fully closed position until power is restored. Do not manually operate damper motor.

Evacuation

Proper evacuation of the system will remove noncondensables and ensure a tight, dry system before charging. Evacuate from both high and low side ports. Never use the system compressor as a vacuum pump. Refrigerant tubes and indoor coil should be evacuated to 500 microns. Always break a vacuum with dry nitrogen. The two possible methods are the deep vacuum method and the triple evacuation method.

Deep Vacuum Method

The deep vacuum method requires a vacuum pump capable of pulling a minimum vacuum of 500 microns and a vacuum gauge capable of accurately measuring this vacuum depth. The deep vacuum method is the most positive way of assuring a system is free of air and liquid water. (See Fig. 34.)

	5000
	4500
	4000							LEAK IN
	3500
MICRONS								SYSTEM
	3000
	2500
	2000
	1500							VACUUM TIGHT
								TOO WET
	1000
	500							TIGHT
								DRY SYSTEM
	0	1	2	3	4	5	6	7
				MINUTES
								C06264

Fig. 34 - Deep Vacuum Graph

Triple Evacuation Method

The triple evacuation method should only be used when vacuum pump is capable of pumping down to 28-in. of mercury and system does not contain any liquid water. Proceed as follows:

1.Pump system down to 28-in. of mercury and allow pump to continue operating for an additional 15 minutes.

2.Close service valves and shut off vacuum pump.

3.Connect a nitrogen cylinder and regulator to system and open until system pressure is 2 psig.

4.Close service valve and allow system to stand for 1 hr. During this time, dry nitrogen will be able to diffuse throughout the system, absorbing moisture.

5.Repeat this procedure. System will then contain minimal amounts of contaminants and water vapor.

Refrigerant Charge

Amount of refrigerant charge is listed on unit nameplate. Refer to Carrier GTAC II; Module 5; Charging, Recovery, Recycling, and Reclamation section for charging methods and procedures. Unit panels must be in place when unit is operating during charging procedure.

Puron→ (R-410A) refrigerant systems should be charged with liquid refrigerant. Use a commercial type metering device in the manifold hose.

!WARNING

UNIT OPERATION AND SAFETY HAZARD

Failure to follow this warning could cause personal injury, death and/or equipment damage.

Puron (R-410A) refrigerant systems operate at higher pressures than standard R-22 systems. Do not use R-22 service equipment or components on Puron refrigerant equipment. Gauge set, hoses, and recovery system must be designed to handle Puron refrigerant. If unsure about equipment, consult the equipment manufacturer.

IMPORTANT: Do not use recycled refrigerant as it may contain contaminants.

No Charge in the System

Use standard evacuating techniques. After evacuating system, weigh in the specified amount of refrigerant (refer to unit nameplate). Verify charge using the charging chart via “Charge in the System.”

Charge in the System

IMPORTANT: The circuit must be running in normal cooling mode with the compressor capacity at 100%. The VFD must be running at max fan speed and indoor airflow must be within specified air quantity limits for cooling (See Appendix D). All outdoor fans must be on and running at high speed. Use the Cooling Service Test Outdoor Fan Override function to start all outdoor fans.

An accurate pressure gauge and temperature-sensing device is required. Charging is accomplished by ensuring the proper amount of liquid subcooling. Connect pressure gauge to the compressor discharge service valve. Connect temperature sensing device to the liquid line between the condenser and the TXV (thermostatic expansion valve), and insulate it so that ambient temperature does not affect reading. Use the cooling charging chart (Fig. 35-36) to determine if additional charge is needed or if some charge needs to be removed from the system.

To Use the Cooling Charging Chart

Use the temperature and pressure readings, and find the intersection point on the cooling charging chart. If intersection point on chart is above line, add refrigerant. If intersection point on chart is below line, carefully recover some of the charge. Recheck suction pressure as charge is adjusted.

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