Bryant 581A Vii. Power Failure, Viii. Refrigerant Charge, A. No Charge, B. Low Charge Cooling

VII. 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.

VIII. REFRIGERANT CHARGE

Amount of refrigerant charge is listed on unit nameplate and in Table 1. Refer to 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. 35-37), add or remove refrigerant until conditions of the chart are met. 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.

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 maintain between 10 and 15 degrees of superheat at the com- pressors. The valves are factory set and should not require re-adjustment.

IX. GAS VALVE ADJUSTMENT

A. Natural Gas

The gas valve opens and closes in response 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 valve pressure tap connection. Install a suitable pressure- measuring device.

4.Set main gas valve to ON position.

5.Set thermostat at setting to call for heat.

6.Remove screw cap covering regulator adjustment screw (see Fig. 38).

7.Turn adjustment screw clockwise to increase pres- sure or counterclockwise to decrease pressure.

LEGEND

TXV — Thermostatic Expansion Valve

Fig. 35 — Cooling Charging Chart — 581A210 Units

LEGEND

TXV — Thermostatic Expansion Valve

Fig. 36 — Cooling Charging Chart — 581A240 Units

LEGEND

TXV — Thermostatic Expansion Valve

Fig. 37 — Cooling Charging Chart — 581A300 Units

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