Bryant 558D III. Indoor Airflow and Airflow Adjustments, Direct Drive Motors

of cooling is satis®ed, the compressor and OFM will be deen- ergized. The damper position will be determined by the supply- air temperature. When the ®rst stage of cooling is satis®ed, there is a 30-second delay before the evaporator fan shuts off. The damper then moves to the fully closed position. When using a continous fan, the damper moves to the minimum position. Additional information on economizer operation is provided in the Ventilation Sequence section on page 27.

Cooling, Units With PARABLADE Economizer

When the outdoor-air is above the enthalpy control setting, and the room thermostat calls for cooling, the compressor con- tactor is energized to start the compressor and the outdoor (condenser) fan motor. The indoor (evaporator) fan motor is energized and the economizer damper moves to the mini- mum position. After the room thermostat is satis®ed the damper will spring return to the fully closed position.

When the outdoor-air is below the enthalpy control setting and the thermostat calls for cooling, the economizer outdoor- air damper is opened proportionally to maintain between 50 and 56 F at the mixed-air sensor. If outside air alone cannot satisfy the cooling requirements, economizer cooling is inte- grated with mechanical cooling. When the room thermostat is satis®ed, the damper will spring return to the full closed position. Additional information on economizer operation is provided in the Ventilation Sequence section on page 27.

Time Guard II Device

If the unit is equipped with accessory Time Guard II recycle timer, the unit will delay 5 minutes between compressor starts.

Controls Kit

Loss-of-Charge/Low-Pressure Switch (LPS) Ð When the liq- uid line pressure drops below 7 psig, the LPS opens 24-v power

to the compressor contactor and stops the compressor. When the pressure reaches 22 psig, the switch resets and the com- pressor is allowed to come back on.

High-Pressure Switch (HPS) Ð When the refrigerant high- side pressure reaches 428 psig, the HPS opens 24-v power to the compressor contactor and stops the compressor. When the pressure drops to 320 psig, the switch resets and the com- pressor is allowed to restart.

Freeze-Protection Thermostat (FPT) Ð When the evaporator- coil leaving refrigerant temperature drops below 30 F, the FPT opens 24-v power to the compressor contactor and stops the compressor. When the leaving refrigerant temperature warms to 45 F, the switch resets and the compressor is allowed to restart.

III. INDOOR AIRFLOW AND AIRFLOW ADJUSTMENTS

CAUTION: For cooling operation, the recommended air¯ow is 300 to 500 cfm per each 12,000 Btuh of rated cooling capacity. For heating operation, the air¯ow must produce a temperature rise that falls within the range stamped on the unit rating plate.

Adjust evaporator-fan speed to meet jobsite conditions. Table 3 shows fan rpm at motor pulley settings. Table 4 shows maximum amp draw of belt drive motor. Refer to Tables 5-18 to determine fan speed settings.

A. Direct Drive Motors

The evaporator-fan motor factory speed setting is shown on label diagram affixed to base unit. If other than factory set- ting is desired, refer to label diagram for motor reconnection.

Table 3 Ð Fan Rpm at Motor Pulley Settings*

UNIT					MOTOR PULLEY TURNS OPEN
558D	0	1¤2	1	11¤2	2	21¤2	3	31¤2	4	41¤2	5
036²	1090	1055	1025	990	960	925	890	860	825	795	760
048²	1185	1150	1115	1080	1045	1015	980	945	910	875	840
060²	1300	1260	1220	1180	1140	1100	1060	1020	980	940	900
072**	1460	1420	1380	1345	1305	1265	1225	1185	1150	1110	1070

*Approximate fan rpm shown.

²Indicates alternate motor and drive package. **Indicates standard motor and drive package.

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