Aprilaire Model 8120 Ventilation Controller Owner's Manual

Safety First

⚠️ WARNING: 120 volts may cause injury from electrical shock. Disconnect power before servicing.

❗ CAUTION: Sudden operation may cause personal injury or property damage. Turn Ventilation Controller to "OFF" before servicing.

Read and Save These Instructions

I. Principle of Operation

The Aprilaire® Ventilation Controller provides an intelligent method for supplying fresh air to your home. It works in conjunction with an Aprilaire® Damper to determine when and for how long to ventilate. This decision-making process involves continuous monitoring of indoor relative humidity, outdoor temperature, and user-adjustable timer settings.

Indoor relative humidity is monitored to prevent high humidity conditions within the home. The controller will not open the damper to the outside air if doing so risks increasing indoor humidity to high levels. Specifically, it is designed to prevent indoor relative humidity from exceeding 60% due to ventilation.

Additionally, if the outdoor air temperature is below 0°F or above 100°F, the motorized normally-closed damper will not open. This feature can be disabled during installation if the installer opts not to use outdoor air temperature as a parameter.

Note on Sensor Replacement:

• If a 'TIME ONLY' resistor is used instead of an Outdoor Temperature Sensor, the controller's operation relies solely on adjustable timer settings, disregarding temperature and humidity limits.
• If a jumper wire is used in place of the Outdoor Temperature Sensor, the controller will ignore temperature settings and base ventilation on indoor relative humidity and user-adjustable timers. In this configuration, ventilation will not occur if indoor relative humidity rises above 55%.

II. Operating Instructions

Your Ventilation Controller is installed in the return duct of your furnace or heat pump. Two primary settings are adjustable: the cycle time interval and the ventilation time within each cycle.

For example, setting the cycle time to 1 hour and the ventilation time knob to 20 minutes will result in 20 minutes of ventilation every hour. It's important to note that this required ventilation period can be met by a heating, cooling, or fan call initiated by your thermostat, or by a fan call initiated by the Ventilation Controller itself.

The following steps detail how to adjust these settings:

1. Setting the Cycle Time Interval

To adjust the cycle time:

• Remove the control knob by pulling it straight out from the controller.
• Remove the cover by gripping its top and bottom edges and pulling it straight out from the base.
• Refer to Figure 1 to locate the cycle time header and jumper.

Figure 1: Cycle Time Configuration

This diagram illustrates the cycle time header and jumper. The header has pins labeled for different cycle time intervals: "1 HR", "3 HR", "2 HR", "4 HR". A jumper is used to select the desired interval.

• The jumper on the 5-pin header determines the cycle time interval, which can be set to 1, 2, 3, or 4 hours. The default setting is 1 hour.
• Move the jumper to your desired setting. The jumper can be removed by pulling it straight out from the header pins.
• Snap the cover back onto the controller and slide the knob back onto its shaft.

2. Setting the Ventilation Time

The knob on the exterior of the controller is used to set the duration of ventilation within the interval established in Step 1.

• The knob settings range from "OFF" (fully counter-clockwise) to "TEST" (fully clockwise).
• While the knob is marked in 15-minute increments, the ventilation time can be adjusted more precisely, to the nearest minute, within each 15-minute interval.

Figure 2: Ventilation Time Knob

This diagram shows the ventilation time knob. It is a dial labeled "MINUTES PER CYCLE" with markings from "0" to "60". The settings include "OFF" and "TEST". Rotating the knob adjusts the ventilation duration within the selected cycle time.

Test Mode: Test mode is intended for checking the device during installation. In Test mode, the Ventilation Controller activates the HVAC fan and opens the damper for one minute, or until the knob is moved from the "TEST" setting, whichever occurs first. After this minute, the controller will not operate again until the knob is moved off "TEST".

III. Outdoor Temperature & Indoor Humidity Control Limits

In a standard installation, your Aprilaire Ventilation Controller utilizes measurements of outdoor temperature and indoor humidity, in addition to user-adjustable timer settings, to govern ventilation.

Outdoor temperature is measured by a sensor located at the fresh air intake duct inlet. Indoor humidity is measured within the return duct by a sensor integrated into the controller.

The controller operates based on the temperature and humidity control limits depicted in Figure 3.

Figure 3: Model 8120 Operating Limits Graph

This graph illustrates the operating limits for the Model 8120. The X-axis represents Outdoor Temperature (°F) ranging from 0°F to 100°F. The Y-axis represents Indoor Relative Humidity (%) ranging from 0% to 55% and beyond. The graph is divided into three sections:

• SECTION A: The controller will not ventilate due to temperature extremes (e.g., very cold or very hot outdoor temperatures).
• SECTION B: The controller will ventilate according to the timer settings, provided temperature and humidity are within acceptable ranges.
• SECTION C: The controller will ventilate only when the heating system is active, according to the timer settings. This section is typically active at lower outdoor temperatures and moderate humidity levels.

IV. Limited Warranty

Your Research Products Corporation Aprilaire® Ventilation Controller is warranted for five (5) years from the date of installation against defects in materials or workmanship.

Research Products Corporation's sole obligation under this warranty is to provide, at no charge, a replacement for any defective Controller returned within five (5) years of installation, and no later than thirty (30) days after the five-year period expires. The defective unit must be returned to your original supplier or to Research Products Corporation, Madison, Wisconsin 53701, along with the installation date.

This warranty does not cover labor costs and does not apply to defects in workmanship or materials supplied by your installer. Implied warranties of merchantability or fitness for a particular purpose are limited to the five-year duration of this warranty.

Research Products Corporation expressly excludes liability for incidental or consequential damages, except for personal injuries, resulting from any breach of implied warranties or this limited warranty.

This limited warranty is void if the unit is not installed by a qualified heating and air conditioning contractor. If the warranty is voided due to improper installation, all disclaimers of implied warranties become effective upon installation.

Some states do not permit limitations on the duration of implied warranties or the exclusion/limitation of incidental or consequential damages, so these exclusions/limitations may not apply to you. This warranty grants specific legal rights, and you may have other rights that vary by state.

Warranty Registration

Please take a few minutes to register your Aprilaire product online at www.aprilaire.com.

If you do not have internet access, please mail a postcard with your name, address, phone number, product purchased, and date of purchase to:

Research Products Corporation
P.O. BOX 1467
Madison, WI 53701

Thank you!

Your Warranty Registration information will not be sold or shared outside of this company.