Ventilation And Fan Cycling - Aprilaire 1720 Installation,Safety & Maintenance Manual

VENTILATION / FAN CYCLING SETTINGS
The Aprilaire Dehumidifier has the option
to monitor HVAC heating, cooling and fan
calls to assure the HVAC fan has
operated a predetermined amount of
time each 1/2, 1, 2 or 3 hours. The
dehumidifier can also open a normally
closed damper in an outdoor air intake to
ventilate during this predetermined
amount of time. This feature will
function even if the dehumidifier is
turned off at the dehumidifier or Model
70 Occupied Space Control. The only way
to disable this feature is by turning the
Cycle Time setting to OFF or turning
power off at the On/Off switch.
SET-UP PROCEDURE
First, set the 1/2, 1, 2 or 3 hour period by
setting the CYCLE PERIOD dip switches to determine how often the dehumidifier should look to
ventilate or cycle the HVAC fan. The factory default setting is 1 hour.
Next, use the CYCLE TIME dial to determine how long during every cycle period the HVAC fan
should operate. Adjust the dial from OFF to between 1 to 60 minutes. This will give you HVAC fan
operation from 1 to 60 minutes every 1/2, 1, 2 or 3 hours. A call for heat, cooling or fan from the
HVAC equipment will often satisfy the run time requirement. If not, the dehumidifier will turn on
the HVAC fan to assure that the cycle time is met. For example: If the building requires
ventilation of 20 minutes every two hours set the CYCLE PERIOD Dip Switch for 2 hours
to ON, turn OFF the 1 HOUR Dip Switch and rotate the CYCLE TIME to 20 minutes. If the
HVAC equipment has only run for 10 minutes, the dehumidifier will turn on the HVAC
fan for 10 minutes at the end of the 2 hours to assure the ventilation / fan cycling time.
Finally, if using the Ventilation Damper, determine if the ventilation should be restricted based
on outdoor temperature. Set the VENT-AUTO / VENT-TIMED dip switch to VENT-AUTO
(see Figure 15) to prevent opening the ventilation damper if the outdoor air is above 100°F,
below 0°F or except with a heat call between 20°F and 0°F. In the VENT-TIMED setting the
ventilation damper is activated regardless of outdoor conditions. Note: The Outdoor
Temperature Sensor (Model 8052) must be installed for this to work.
You can also check the wiring of the dehumidifier to the HVAC equipment. If you rotate the
CYCLE TIME dial to TEST, the HVAC fan should come on and the Ventilation Damper
(if equipped) should open. DO NOT leave the CYCLE TIME in TEST.
10
FIGURE 12
THERMOSTAT
R
C
G
W
Y
OPTIONAL OUTDOOR
TEMPERATURE SENSOR
(Model 8052)
90-968
OPTIONAL
VENTILATION
24 VAC
DAMPER
(10 VA min)
TRANSFORMER
HVAC EQUIPMENT
R
C
WIRE NUT
G
W
Y
FIGURE 13
FIGURE 14
FIGURE 15
OFF
MODEL 70
HVAC FAN
WHL HOUSE
VENT-AUTO
DEHUMIDIFIER
CONTROL
(shown set
to 1 hour)
CYCLE PERIOD
30 MIN.
1 HOUR
2 HOUR
3 HOUR
90-783C
(shown set to
30 minutes)
30
MIN.
0 60
MIN MIN. MIN.
OFF TEST
CYCLE TIME
90-783C
SYSTEM SETUP
ON
MODEL 70
HVAC FAN
CONVERTIBLE
VENT-TIMED
90-969