Unit installation

IOMM ACZ1-2 ACZ 010A through 039A 33
T2: Transition from Auto to Pumpdown
Requires any of the following:
• Keypad Enable = Off OR
• BAS Enable = Off OR
• Remote Switch = Off OR
• Pumpdown Alarm Active
T3: Transition from Pumpdown to Off
Requires any of the following:
• Unit Alarm OR
• Unit Switch Off OR
• All compressors off
T4: Transition from Auto to Off
Requires any of the following:
• Unit Alarm OR
• Unit Switch Off
• Both compressors disabled via manual setpoint
Evaporator Fan State Control
Operation of the evaporator fan output is controlled by the state-transition diagram shown
below.
Figure 11, Fan Output State
Off
Run Start
Unit State=Auto
Unit State = Off
[Evap State = Start AND
Flow Switch Closed] for
time > Evap Recirc Tmr
Unit State = Off
Evaporator Fan Output State
Diagram
Condenser Fans
Condenser fans are staged up and down based on the fan stage setpoint. These setpoints
define pressures at which fans should start or stop. Comments for “fan 3” apply to 3-fan
units only.
fan 1 will start with the first compressor when the ambient temperature is greater than 75°F.
Below 75°F, this fan starts when the condenser pressure gets up to the Stage #1 On setpoint.
fan 2 will start when the condenser pressure gets up to the Stage #2 On setpoint, and fan 3
will start when the condenser pressure gets up to the Stage #3 On setpoint.