Specifications

F) DX cooling only
Fan Operation
The supply fan shall run continuously in the occupied and tenant (unoccupied) override modes. The fan shall
cycle with calls for cooling or heating in the unoccupied mode.
Cooling Operation
When the space temperature exceeds the cooling setpoint, the compressor shall be started. The compressor
shall run until the space temperature falls 0.5°F below the cooling setpoint. Compressor operation shall be
controlled with an integrated run timer such that once engaged, the compressor shall operate for a minimum of
2 minutes before disengaging. This run timer also provides a 3-minute minimum OFF time delay (anti short-
cycle timer).
If the outdoor air temperature falls below 59°F, the compressor shall be disengaged when the minimum run
time of 2 minutes is complete. The compressor shall remain disengaged until the outdoor air temperature
exceeds 61°F AND the minimum off time of 3 minutes has elapsed.
If the discharge air temperature falls below 50°F OR the optional refrigerant low limit switch trips, the
compressor shall be immediately disengaged, regardless of the minimum run timer status. The compressor
shall remain disengaged until the low limit switch opens AND the discharge air temperature is above 52°F
AND the minimum off time of 3 minutes has elapsed.
Heating Operation
The supply fan shall be engaged when the space temperature falls below the heating setpoint (unoccupied
mode).
Outdoor Air Damper Control
The outdoor air damper shall be closed in the unoccupied mode, regardless of the space temperature
conditions.
The outdoor air damper shall be closed if the discharge air temperature falls below 53°F and remain closed
until the discharge air rises above 55°F.
The outdoor air damper shall be closed if the space temperature falls more than 3°F below the heating
setpoint. The damper will not open until the space temperature rises within 2°F of the heating setpoint.
The outdoor air damper shall close to minimum position when the outdoor air temperature exceeds 68°F.
The outdoor air damper shall be controlled with a proportional control loop based upon the discharge air
temperature. The outdoor air damper shall begin to modulate open from minimum position when the discharge
air temperature exceeds 55°F and shall be fully open at 59°F. Except as noted in the paragraphs above, the
outdoor air damper shall not close beyond minimum position during occupied operation.
Safeties - Low Limit Conditions
If the discharge air temperature falls below 53°F, the unit enters ventilation low limit mode. This shall drive the
outdoor air damper closed. This damper shall not open until the discharge air temperature exceeds 55°F.
If the discharge air temperature falls below 50°F, the unit enters refrigeration low limit mode. This shall
immediately disengage the compressor, regardless of the minimum on timer status. The compressor shall not
be allowed to operate until the discharge air temperature exceeds 52°F AND the minimum off time has
elapsed.
7/1/03 Part Number 011-200001-003 Page 14