Aprilaire 1750A Installation Instructions Manual page 18

VENTIlATION OR AIR CyClING
SEQUENCE Of OPERATION
VENT-TIMED, HVAC INITIATES VENTIlATION
• T he ventilation damper will open whenever there is an HVAC fan (Gs) or heat (W) call, and will stay open until the Cycle Time (during the Cycle
Period) has been met .
• W hen the HVAC heat or fan call has ended or when the ventilation time requirement has been met, the ventilation damper will close.
• T wo minutes must elapse following the end of a HVAC fan or heat call before the dehumidifier can initiate a ventilation cycle.
VENT-TIMED, DEHUMIDIfIER INITIATES VENTIlATION
• W hen the amount of time remaining in the Cycle Period is equal to the amount of time needed to satisfy the Cycle Time, the HVAC fan turns
on and the ventilation damper opens .
• W hen the ventilation time requirement has been met, the HVAC fan turns off and the ventilation damper closes.
• T o prevent short cycling the fan, a ventilation cycle will not start unless there are at least 2 minutes remaining in the Cycle Period.
DEHUMIDIfICATION DURING VENTIlATION
When installed in a Single Zone application and there is no External or Remote Control, the dehumidifier can be used to pre-condition the
ventilation air .
• T he dehumidifier damper output and dehumidifier blower turn on whenever ventilation is active.
• T he dew point of the air is measured 3 minutes after the dehumidifier blower is turned on and every 15 seconds while the blower is running.
• I f the dew point of the air is above the setting on the control knob, the compressor turns on and the green Status LED switches to solid
illumination .
• W hen the dew point of the air falls below the control knob set point, the compressor turns off and the Status LED flashes.
VENT-AUTO
Ventilation in the Vent-Auto configuration is functionally the same as Vent-Timed operation, with the exception of the temperature limits applied
to the incoming air .
• I f the incoming air temperature is greater than or equal to 100°F, the ventilation damper closes. If the temperature drops to 95°F or lower
during the same ventilation cycle, the ventilation damper will open .
• I f the incoming air temperature is less than or equal to 0°F, the ventilation damper closes. If the temperature increases to 5°F or higher during
the same ventilation cycle and the ventilation cycle was initiated by a HVAC heat (W) call, the ventilation damper will open .
• I f the air temperature is less than or equal to 20°F and above 0°F, the ventilation damper will close unless a HVAC heat (W) call initiates
the ventilation cycle . If the air temperature drops to 0°F or below during the same ventilation cycle, the ventilation damper closes . If the
temperature rises to 25°F or higher during the same ventilation cycle, the ventilation damper will open .
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