Bryant 551A VIII. Power Failure, IX. Refrigerant Charge, Filter Drier, XI. Protective Devices

If the CONFIG button is pressed and held for more than 30 seconds and released, the EconoMi$er controller will enable the enthalpy comparison strategy (with outdoor air enthalpy and return air enthalpy sensors installed).

VIII. 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.

IX. REFRIGERANT CHARGE

Amount of refrigerant charge is listed on unit nameplate and in Table 1. 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.

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

A. No Charge

Use standard evacuating techniques. After evacuating sys- tem, weigh in the specified amount of refrigerant (refer to Table 1).

B. Low Charge Cooling

Using cooling charging chart (see Fig. 35), add or remove refrigerant until conditions of the chart are met. Note that charging chart is different from those normally used. An accurate pressure gage and temperature-sensing device is required. Charging is accomplished by ensuring the proper amount of liquid subcooling. Measure liquid line pressure at the liquid line service valve using pressure gage. Connect temperature sensing device to the liquid line near the liquid line service valve and insulate it so that outdoor ambient temperature does not affect reading.

C. To Use The Cooling Charging Chart

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

								BOTH CIRCUITS
				ALL OUTDOOR FANS MUST BE OPERATING
(DEG F)	140
VALVE	120
			ADD		CHARGE		IF ABOVE CURVE
LIQUIDAT	100
TEMPERATURELIQUID
	80
	60								REDUCE CHARGE IF BELOW CURVE
	40
		100				150	200			250	300	350	400
	50

LIQUID PRESSURE AT LIQUID VALVE (PSIG)

Fig. 35 — Cooling Charging Chart

NOTE: Indoor-air CFM must be within normal operating range of unit. All outdoor fans must be operating.

The TXV (thermostatic expansion valve) is set to main- tain between 15 and 20 degrees of superheat at the compres- sors. The valves are factory set and should not require re-adjustment.

D. Perfect Humidity™ System Charging

The system charge for units with the Perfect Humidity option is greater than that of the standard unit alone. The charge for units with this option is indicated on the unit nameplate drawing. To charge systems using the Perfect Humidity Dehumidification package, fully evacuate, recover, and re-charge the system to the nameplate specified charge level. To check or adjust refrigerant charge on systems using the Perfect Humidity Dehumidification package, charge per the standard subcooling charts. The subcooler MUST be deenergized to use the charging charts. The charts reference a liquid pressure (psig) and temperature at a point between the condenser coil and the subcooler coil. A tap is provided on the unit to measure liquid pressure entering the sub- cooler (leaving the condenser).

X. FILTER DRIER

Replace whenever refrigerant system is exposed to atmosphere.

XI. PROTECTIVE DEVICES

A. Compressor Protection

Overtemperature

Each compressor has an internal protector to protect it against excessively high discharge gas temperatures.

Overcurrent

Each compressor has internal line break motor protection.

Crankcase Heater

All units are equipped with a 70-watt crankcase heater to prevent absorption of liquid refrigerant by oil in the crank- case when the compressor is idle. The crankcase heater is energized whenever there is a main power to the unit and the compressor is not energized.

IMPORTANT: After prolonged shutdown or servicing, ener- gize the crankcase heaters for 24 hours before starting the compressors.

Compressor Lockout

If any of the safeties (high-pressure, low-pressure, freeze protection thermostat, compressor internal thermostat) trip, or if there is loss of power to the compressors, the CLO (com- pressor lockout) will lock the compressors off. To reset, man- ually move the thermostat setting.

B. Evaporator Fan Motor Protection

A manual reset, calibrated trip, magnetic circuit breaker protects against overcurrent. Do not bypass connections or increase the size of the breaker to correct trouble. Determine the cause and correct it before resetting the breaker.

C. Condenser-Fan Motor Protection

Each condenser-fan motor is internally protected against overtemperature.

D. High- and Low-Pressure Switches

If either switch trips, or if the compressor overtemperature switch activates, that refrigerant circuit will be automati- cally locked out by the CLO. To reset, manually move the thermostat setting.

—29—