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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 output Y1
is energized; terminal Y1 at CAS090 unit receives 24-v.
24-v received at CADM1 terminal Y. If anti-recycle time
delay period has not expired, CADM1 relay will remain
open, de-energizing Solenoid Valve Relay (SVR) and
preventing compressor start. When safety pressure
switches are closed and CADM1 time delay expires,
CADM1 relay closes, SVR and compressor contactor C1
are energized; Compressor Relay Timer (CTR) is closed
and Digital Cycle Timer (CTD) is energized commanding
Digital Compressor Solenoid (DCS) on, liquid line
solenoid valve LLSV opens, all outdoor fan motors start
and Compressor starts part load operation.
On thermostat call for Stage 2 Cooling, thermostat output
Y2 is energized CTR receives 24- - v at terminal 1 changing
contacts to open. CTD is de- - energized and commands
DCS off, Compressor operates at full load.
As space cooling load is satisfied, thermostat outputs Y2 and
Y1 are sequentially de- - energized, removing 24- - v at
CAS090 terminals Y1 and Y2. Compressor resumes part
load operation on Y2 opening. On Y1 opening, Compressor
1 stops, all outdoor fan motors stop and SVR is
de- - energized. Liquid Line solenoid valve is de- - energized
and valve closes. CADM1 begins its three- - minute
anti- - recycle time delay.
If either the Low Pressure Switch or High Pressure Switch
opens while thermostat output Y1 or Y2 remain energized,
the compressor contactor is de-energized, the compressor
stops 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; disconnect unit power and allow compressor to
cool. See Service section for further details.
20
Cooling, Unit With Economizer —
Refer to fan coil unit installation instructions and
economizer
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
S Condenser coil cleanliness checked.
S Return air filter replacement
S Outdoor hood inlet filters cleaned
S Belt tension checked
S Belt condition checked
S Pulley alignment checked
S Fan shaft bearing locking collar tightness checked
S 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
S Condenser fan motor mounting bolts tightness
S Compressor mounting bolts
S Condenser fan blade positioning
S Control box cleanliness and wiring condition
S Wire terminal tightness
S Refrigerant charge level
S Evaporator coil cleaning
S Evaporator blower motor amperage
Heating
S Power wire connections
S Fuses ready
S Manual-reset limit switch is closed
Economizer or Outside Air Damper
S Inlet filters condition
S Check damper travel (economizer)
S Check gear and dampers for debris and dirt
Specifications are subject to change without notice.
accessory
installation
501 01 3600 01
instructions
for
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