Amana PGB58B, PGC(24-60)B Checking External Static Pressure, Changing Blower Speeds PGC Units

With a properly designed system, the proper amount of temperature rise will normally be obtained when the unit is operated at rated input with the recommended blower speed.

If the correct amount of temperature rise is not obtained, it may be necessary to change the blower speed. A higher blower speed will lower the temperature rise. A slower blower speed will increase the temperature rise.

NOTE: Blower speed MUST be set to give the correct air temperature rise through the furnace as marked on the rating plate.

Important Note: If an installation uses a different blower speed for cooling than is used for heating, do not set the thermostat fan switch to ON (constant fan operation) during the heating season without first confirming the cooling fan speed will give a temperature rise within the limits listed on the unit nameplate. Temperature rises outside the limits listed could result in premature heat exchanger failure.

Checking External Static Pressure

The total external static pressure must be checked on this unit to determine if the airflow is correct.

Changing Blower Speeds (PGC Units)

WARNING

To avoid personal injury or death due to electric shock, remove electrical power from the unit before changing speed taps on the blower motor.

PGC-B models include a BPM (brushless permanent magnet) motor. Under identical conditions, it operates at a lower power consumption than most PSC motors. Within the allowable range of external static pressures, the BPM motor will automatically adjust its RPM to de- liver the CFM listed in the blower performance table. As static pressure increases, the RPM, current draw, and operating sound level of the motor will also increase. External static pressures in excess of those listed on the nameplate may result in unsatisfactory operation, equipment damage, and/or loss of warranty coverage.

The PGC-B models also include a speed tap board lo- cated on the blower housing. The speed tap settings have been factory selected according to unit size and performance. Field select taps are provided on the speed tap board to assist the final installer. The ADJ. tap is factory set for normal (NORM) operation. Three LED’s are provided on the speed tap board. These lights indi- cate to the servicer which mode of operation the motor is experiencing, that is Heating (W1), Fan Only (G) or Cooling (Y and G).

Refer to the wiring diagram on the unit to verify speed tap settings.

Changing Blower Speeds (PGB Units)

WARNING

To avoid personal injury or death due to electric shock, remove electrical power from the unit before changing speed taps on the blower motor.

A multi-speed motor is used in the furnace blower. It provides easy speed selection for both heating and cool- ing air flow. Section II shows the CFM and E.S.P. rela- tionship for proper selection of heating and cooling speeds. Cooling speed should be set for about 400 CFM per ton cooling capacity.

Refer to the Wiring Diagram on the furnace to connect the proper wires to the correct motor leads. All unused motor leads must be taped or securely covered with wire nuts.

Check Limit And Fan Control

1.Check limit control (Figure 18) operation after 15 minutes of operation by blocking the return air grille(s).

a.After several minutes the main burners must go OFF. Blower will continue to run.

b.Remove air restrictions and main burners will re- light after a cool down period of a few minutes.

2.Adjust the thermostat setting below room tempera- ture.

a.Main burners must go off.

b.Circulating Air Blower should continue to run briefly until supply air temperature drops to approximately 90-100° F.

Fan and limit controls are preset at the factory. The con- trol is set for the fan to go off at 90-100° F:

NOTE: If necessary, adjust fan ON/OFF settings to ob- tain satisfactory comfort level. The fan comes on at ap- proximately 125° F.

WARNING

To avoid personal injury, property dam- age, fire, or premature failure of the heat exchanger, do not adjust the limit con- trol, which is set at the factory.

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