10007791 10.07
B2204536A
DEHUMIDIFIER SEQUENCE OF OPERATION
IF THE DEHUMIDIFIER IS NOT WIRED TO THE HVAC EQUIPMENT, THE DEHUMIDIFIER WILL SAMPLE AT THE END OF THE
CYCLE PERIOD.
With 4 minutes left in the Cycle Period, the dehumidifier will turn on the dehumidifier blower for 3 minutes. During this time the
temperature and relative humidity are measured and the dewpoint is calculated. If the dewpoint is higher than the setting at the
Control Knob then the dehumidifier compressor will turn on and the dehumidifier will run until it reaches set point.
After reaching the set point, the dehumidifier will not sample again until the end of the next Sample Period.
For example, if the Sample Period is set for 1 hour, the dehumidifier will sample at the end of the hour. Once the dehumidifier
reaches set point and shuts off, the dehumidifier will not sample again until the end of the next hour.
IF THE DEHUMIDIFIER IS WIRED INTO THE HVAC EQUIPMENT, THE DEHUMIDIFIER WILL SAMPLE THE FIRST TIME THE HVAC
EQUIPMENT RUNS IN THE CYCLE PERIOD OR AT THE END OF THE CYCLE PERIOD IF THE HVAC EQUIPMENT DOES NOT RUN.
For example, if the Cycle Period is set to 1 hour and the air conditioner starts 15 minutes into that hour, the dehumidifier will
sample when the air conditioner starts. Once the dehumidifier begins dehumidifying, it will run until set point is reached. If the
dehumidifier samples and determines that dehumidification is not needed, it will not sample again until the next Cycle Period.
DAMPER SEQUENCE OF OPERATION
In the Central/Zoned installation 4 motorized dampers are used to control the airflow through the dehumidifier. The dampers are
energized when the HVAC equipment is running. This means that when the HVAC equipment is running, the dampers are in the
central position. When the HVAC equipment is not running, the dampers are in the zoned position.
VENTILATION OR AIR CYCLING SEQUENCE OF OPERATION
If the dehumidifier is providing outdoor air ventilation or air cycling, it is monitoring the HVAC equipment to provide the amount
of HVAC fan run time that has been set by the Cycle Time during the Cycle Period.
If an outdoor air damper has not been installed then the dehumidifier is providing air cycling. The dehumidifier will monitor the
HVAC system and if the system has not run for the specified Cycle Time within the Cycle Period, the dehumidifier will energize
the HVAC fan through the G terminal to provide the desired amount of fan run time.
For example, if the Cycle Time is set for 10 minutes and the Cycle Period is set for 1 hour then the dehumidifier will provide
10 minutes of air cycling or outdoor air ventilation. If the HVAC system runs for 5 minutes during this hour then the dehumidifier
will energize the fan for an additional 5 minutes.
If an outdoor air damper has been installed, then the Aprilaire dehumidifier is providing outdoor air ventilation. The dehumidifier
will open the outdoor air damper whenever the HVAC system is running, up to the amount of time specified by the Cycle Time.
The dehumidifier will energize the HVAC fan and open the outdoor air damper to provide the desired ventilation time if the HVAC
system has not run for the specified Cycle Time. During ventilation, the dehumidifier blower will operate and the unit will
dehumidify if necessary.
If an Outdoor Temperature Sensor has been installed, then the dehumidifier will use the outdoor temperature to determine if the
outdoor air damper is to be opened. If the outdoor temperature is above 100°F the damper will not open. If the temperature is
between 20°F and 0°F the damper will only open with a heat call. If the outdoor temperature is below 0°F, the damper will not
open. If the Outdoor Temperature Sensor is not installed then the temperature is not considered in opening the damper.
RESEARCH PRODUCTS CORPORATION
P.O. BOX 1467 • MADISON, WI 53701-1467 • PHONE: 800/334-6011 • FAX: 608/257-4357 •
www.aprilairecontractor.com
