Carrier 38AUZ appendix Operating Sequence, Routine System Maintenance, Base Unit Controls, Heating

OPERATING SEQUENCE

Base Unit Controls

Indoor (Supply) Fan

The indoor fan contactor (IFC) is remotely located at the fan coil or fan section. If the thermostat fan operation is selected as Continuous, the IFC is energized and the indoor (supply) fan motor runs continuously. If the thermostat fan operation is selected as Automatic, the IFC will be energized on a call for Cooling; indoor (supply) fan motor runs. When thermostat call for Cooling is satisfied, the IFC is de-energized and indoor (supply) fan motor stops.

Cooling, Unit Without Economizer

On a thermostat call for Cooling, IFC will be energized and indoor (supply) fan motor runs. Thermostat contact TC1 closes; terminal Y1 at 38AU unit receives 24-v. 24-v received at CADM terminal Y. If anti-recycle time delay period has not expired, CADM relay will remain open, preventing compressor start. When safety pressure switches are closed, the liquid line solenoid valve opens. When CADM time delay expires, the compressor contactor is energized; both outdoor fan motors start and compressor starts.

When space cooling load is satisfied, thermostat contacts TC1 open, removing 24-v at 38AU terminal Y. Compressor and outdoor fan motors stop. Liquid line solenoid valve is de-energized and valve closes. CADM begins its three-minute anti-recycle time delay.

If either the Low Pressure Switch or High Pressure Switch opens while thermostat contact TC1 remains closed, the compressor contactor is de-energized (both fan motors and compressor stop) and liquid line solenoid is de-energized (valve closes). CADM initiates a TRIP event (cooling demand sensed at CADM terminal Y but no current is measured at T1, T2, T3 motor sensors); CADM relay opens and RED LED is illuminated. TRIP condition maintains lockout of compressor operation until CADM is manually reset. Reset CADM by cycling unit main power.

Complete system shutdown may be caused by loss of main power, open compressor internal overload, open low-pressure or high-pressure switch, or a fault detected by the CADM logic. Compressor operation without cooling may indicate the compressor’s ASTP feature is active (unit sizes 12 and 14 only); disconnect unit power and allow compressor to cool. See Service section for further details.

Cooling, Unit With Economizer

Refer to fan coil unit installation instructions and economizer accessory installation instructions for operating sequences when system is equipped with accessory economizer.

Heating

Refer to fan coil unit installation instructions and accessory heating device installation instructions for operating sequences in heating mode.

ROUTINE SYSTEM MAINTENANCE

These items should be part of a routine maintenance program, to be checked every month or two, until a specific schedule for each can be identified for this installation:

Quarterly Inspection (and 30 days after initial start)

Indoor section

•Condenser coil cleanliness checked.

•Return air filter replacement

•Outdoor hood inlet filters cleaned

•Belt tension checked

•Belt condition checked

•Pulley alignment checked

•Fan shaft bearing locking collar tightness checked

•Condensate drain checked

Seasonal Maintenance

These items should be checked at the beginning of each season (or more often if local conditions and usage patterns dictate):

Air Conditioning

•Condenser fan motor mounting bolts tightness

•Compressor mounting bolts

•Condenser fan blade positioning

•Control box cleanliness and wiring condition

•Wire terminal tightness

•Refrigerant charge level

•Evaporator coil cleaning

•Evaporator blower motor amperage

Heating

•Power wire connections

•Fuses ready

•Manual-reset limit switch is closed

Economizer or Outside Air Damper

•Inlet filters condition

•Check damper travel (economizer)

•Check gear and dampers for debris and dirt

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