Carrier 50MP62L-10R, MPE62L-10R Gas Valve Adjustment, Protective Devices, Main Burner Removal

PULLEY ALIGNMENT Ð For proper belt life, the motor and fan pulleys must be properly aligned. To check, ®rst turn off unit power. Place a straightedge against the motor and fan pulleys. See Fig. 62. If the pulleys are properly aligned, the straightedge should be parallel to the belts.

If they are not parallel, check that the motor shaft and fan shaft are parallel. If they are not, adjust the motor plate adjusting bolts until they are.

After verifying that the shafts are parallel, loosen the set- screws on the motor pulley. Move pulley on the shaft until the pulleys are parallel. To move the sheave on the shaft, loosen the belts. If necessary, blower sheave can also be moved on the shaft.

6.Remove screw cap covering regulator adjustment screw (see Fig. 63).

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

8.Once desired pressure is established, set thermostat set- ting for no call for heat, turn off main gas valve, remove pressure-measuring device, and replace 1¤8-in. pipe plug and screw cap.

Fig. 62 Ð Pulley Alignment

Gas Valve Adjustment

NATURAL GAS Ð The gas valve opens and closes in re- sponse to the PIC control or limit control.

When power is supplied to valve terminals D1 and C2, the main valve opens to its preset position.

The regular factory setting is stamped on the valve body (3.3 in. wg).

To adjust regulator:

1.Set thermostat 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 pres- sure 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.

Fig. 63 Ð Gas Valve

Main Burners Ð For all applications, main burners are factory set and should require no adjustment.

MAIN BURNER REMOVAL

1.Shut off (®eld-supplied) manual main gas valve.

2.Shut off power to unit.

3.Remove gas section access door, door frame, and corner post.

4.Disconnect gas piping from gas valve inlet.

5.Remove wires from gas valve.

6.Remove wires from rollout switch.

7.Remove sensor wire and ignitor cable from IGC board.

8.Remove 2 screws securing manifold bracket to basepan.

9.Remove 2 screws that hold the burner support plate flange to the vestibule plate.

10.Lift burner assembly out of unit.

Protective Devices

COMPRESSOR PROTECTION

Overcurrent Ð Each compressor has one manual reset, cali- brated trip, magnetic circuit breaker. Do not bypass connec- tions or increase the size of the circuit breaker to correct trouble. Determine the cause and correct it before resetting the breaker.

Crankcase Heater Ð Each compressor has a crankcase heater to prevent absorption of liquid refrigerant by oil in the crank- case when the compressor is idle. Since 115-v power for the crankcase heaters is drawn from the unit control circuit, main unit power must be on for the heaters to be energized.

IMPORTANT: After a prolonged shutdown or service job, energize the crankcase heaters for 24 hours before starting the compressor.

Compressor Lockout Ð If any of the safeties (high-pressure, or low-pressure) trip, or if there is a loss of power to the compressors, the compressors will be locked out. To reset, consult the controls and troubleshooting literature for the appropriate unit for details.

EVAPORATOR-FAN MOTOR PROTECTION Ð 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.

52