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I. PRINCIPLE OF OPERATION
With your purchase of the Aprilaire
®
Ventilation Controller, you have invested in an
intelligent way of providing fresh air to your home. Working in conjunction with an Aprilaire
®
Damper, the Ventilation Controller makes decisions regarding when – and how long – to
ventilate. It does this through continuous monitoring of indoor relative humidity, outdoor
temperature, and user-adjusted timer settings.
Indoor relative humidity is monitored to help prevent high humidity conditions inside your
home. The Aprilaire
®
Ventilation Controller will not open the damper to the outside air if
there is a chance of raising the humidity inside the house to high levels. The Aprilaire
®
Ventilation Controller is designed to prevent indoor relative humidity levels from increasing
beyond 60% due to ventilation.
If the outdoor air temperature is below 0°F or above 100°F, the motorized normally-closed
damper to the outside will not be opened. This feature can be disabled at installation if the
installer chooses not to use outdoor air temperature as a parameter.
II. OPERATING INSTRUCTIONS
Your Ventilation Controller is installed in the return duct of your furnace or heat pump. There
are two settings that are adjustable: the cycle time and the ventilation time within cycle.
Here’s how this works: if you set the cycle time to 1 hour and the ventilation time knob to
20 minutes, you will get 20 minutes of ventilation every hour. It is important to understand
that the ventilation requirement – 20 minutes per hour in this example – may be satisfied by a
heating, cooling, or fan call initiated by your thermostat, or from a fan call initiated by the
Ventilation Controller itself. The following steps explain how to adjust these settings.
1. SETTING THE CYCLE TIME INTERVAL
• Remove the knob by
pulling it straight out
from the controller.
Remove the cover by
grabbing along the
top and bottom
edges of the cover
and pulling straight
out from the base.
Refer to Figure 1 to
locate the cycle time
header & jumper.
• The jumper on the 5 pin header determines the cycle time interval. The interval can be
1, 2, 3 or 4 hours. (The default setting is 1 hour.)
• Move the jumper to the desired setting. The jumper can be removed by pulling it straight
out from the header pins.
• Snap the cover back on the controller and slide the knob onto the shaft.
2. SETTING THE VENTILATION TIME
• The knob on the exterior of the controller
is used to set the ventilation time within the
interval you set in Step 1.
• The knob settings range from “OFF” which is all
the way counter-clockwise, to “TEST”
†
which is all
the way clockwise. While labeled in 15 minute
increments, the controller may be adjusted within
the 15 minute interval to the nearest minute.
†Test mode is used to check the device at installation. In Test mode
the Ventilation Controller activates the HVAC fan and opens the
damper for one minute or until the knob is taken off the “Test”
setting, whichever occurs first. After the minute has passed, the
Ventilation Controller will not work until the knob is taken off “Test.”
MINUTES PER CYCLE
15
45
30
TEST
0
60
VENTILATION CONTROLLER
OFF
FIGURE 2 – Ventilation Time
90-702
III. OUTDOOR TEMPERATURE & INDOOR HUMIDITY
CONTROL LIMITS
In a standard installation, your Aprilaire Ventilation Controller will use measurements of
Outdoor Temperature and Indoor Humidity, along with the user-adjustable timer settings, to
determine when to ventilate. Outdoor Temperature is measured with a sensor placed at the
inlet of the fresh air intake duct. Indoor Humidity is measured in the return duct with a sensor
built into the Controller. In conjunction with the timer settings, the Controller then operates
according to the temperature and humidity control limits shown in Figure 3 below.
10005991
WIRING AND
JUMPER
CONFIGURATION
CYCLE TIME
1 HR 3 HR
2 HR 4 HR
TO STAT
TO HVAC
TO HVAC
GS
W
G
H
CRDDTT
TO HVAC
DAMPER
TEMP
SENSOR
OUTDOOR
TEMPERATURE
SENSOR
24VAC
A
/
A
CYCLE TIME
1 HR 3 HR
2 HR 4 HR
90-698
FIGURE 1 – Cycle Time
SECTION A
SECTION B
SECTION C
100
20
0
50
55
INDOOR RELATIVE HUMIDITY (%)
OUTDOOR TEMPERATURE (°F)
SECTION A
FIGURE 3 – Model 8120 Operating Limits
90-713
SECTION A: Controller will not ventilate due to temperature extremes
SECTION B: Controller will ventilate according to timer settings
SECTION C: Controller will ventilate only when heating is on according to the timer settings