Aprilaire 1770A - Page 18

VENTILATION OR AIR CYCLING (CONTINUED)
SEQUENCE OF OPERATION
VENT-TIMED, HVAC INITIATES VENTILATION
•The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.
•WhentheHVACheatorfancallhasendedorwhentheventilationtimerequirementhasbeenmet,theventilationdamperwillclose.
•Two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
•When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.
•Whentheventilationtimerequirementhasbeenmet,theHVACfanturnsoffandtheventilationdampercloses.
•To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.
•Thedehumidifierdamperoutputanddehumidifierblowerturnonwheneverventilationisactive.
•The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.
•If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.
•When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.
•If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.
•If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.
•If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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