Carrier 38AUZ User Manual download pdf (Page 18)

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

1 2 ... 13 14 15 16 17 18 19 20 21 22 23 ... 27 28

Comments to this Manuals

No comments

Carrier 38AUZ User Manual Page 18

Comments to this Manuals

Related products and manuals for Conditioners Carrier 38AUZ