Aprilaire 8120A & 8126A Digital Ventilation Controller
Safety & Installation Instructions
READ AND SAVE THESE INSTRUCTIONS
Safety Instructions
⚠️ DANGER
ATTENTION INSTALLER: To prevent serious injury from electrical shock this product must be installed by a qualified HVAC contractor.
120 volts can cause serious injury from electric shock. Disconnect electrical power to the HVAC system before proceeding.
⚠️ CAUTION
- Do not mount the Ventilation Controller on the supply plenum or duct. The unit can lose its calibration when exposed to elevated temperatures.
- When installing the Ventilation Controller on downflow furnaces, ensure that the blower continues to run after the heat call is satisfied to prevent high temperatures from damaging the Control circuit board.
- Do not mount the Ventilation Controller downstream from any fresh air intake port, humidifier or bypass outlet. False humidity conditions will cause the Ventilation Controller to operate incorrectly.
⚠️ WARNING
Sharp metal edges can cause serious injury from cuts. Use gloves when cutting plenum openings and handling ductwork.
Specifications
| Operating temperature range | 20-160°F |
| Maximum current through VENT relay | 2A |
| Input voltage | 22-30 VAC |
| Minimum VA required | 2.0 VA |
Overview
The ventilation controller brings in fresh air and activates the HVAC fan to cycle the fresh air throughout the home. The controller is designed to meet the ASHRAE 62.2-2010 standard for ventilation. The ventilation mode selection allows for time only operation or for temperature and humidity limits to be applied to the incoming air.
Mounting Location
The controller must be installed in the return duct, at least 6 inches upstream of the fresh air intake opening, the humidifier if present, and/or the humidifier bypass duct opening.
Figure 1 - Typical Attic Installation
Diagram shows a typical attic installation with components arranged from left to right: FRESH AIR INTAKE HOOD W/SCREEN, MOTORIZED DAMPER, FRESH AIR INTAKE DUCT, FILTER, FURNACE/AIR HANDLER, SUPPLY PLENUM. The VENTILATION CONTROLLER is shown mounted on the RETURN DUCT, approximately 6 inches upstream of the FRESH AIR INTAKE DUCT.
Figure 2 - Typical Basement Installation
Diagram shows a typical basement installation with components arranged from left to right: FRESH AIR INTAKE HOOD W/SCREEN, FRESH AIR INTAKE DUCT, MOTORIZED DAMPER, FILTER, FURNACE/AIR HANDLER, HUMIDIFIER, SUPPLY DUCT. The VENTILATION CONTROLLER is shown mounted on the RETURN DUCT, approximately 6 inches upstream of the FRESH AIR INTAKE DUCT and the HUMIDIFIER.
Mounting Controller
Disassemble the Controller
Remove the knob. Remove the cover by pulling at the bottom and swinging out and up.
Mount Controller to Duct
After the location of the controller is selected, drill a 3/4 inch hole for the RH sensor (the RH sensor extends from the back of the controller). Before removing the adhesive backing, use the controller to mark the mounting holes and place anchors if applicable. Clean the mounting surface of the duct, remove the adhesive backing from the gasket on the controller, and secure the controller to the duct making sure to align mounting holes and the RH sensor with the drilled hole.
Mounting to Metal Duct
Use field supplied sheet metal screws to secure controller to duct.
Mounting to Duct Board
Use field supplied screws and anchors to secure controller to duct.
Make sure the controller sensor gasket is sealed tightly around the drilled hole. Do not install the controller without the gasket.
Figure 3 - Fiber and Sheet Metal Duct Mount
Diagram shows the controller with its cover removed, indicating a 3/4 inch diameter hole for the sensor. It also shows the controller body and the separate cover.
Note: Controller Replacement – When replacing an 8120 with an 8120A, the duct opening left by the removed controller must be covered completely. Locate and install the new controller as instructed above.
Ductwork & Damper Installation
CAUTION
- Sharp edges may cause serious injury from cuts. Use care when cutting openings and handling duct work.
- Install damper in fresh air duct as close to the return duct as possible.
- Do not force damper blades by hand, as damage may occur.
Ductwork Specifications
- Insulated duct of at least R-4 insulating value with a continuous vapor barrier must be used for the intake duct. The vapor barrier must be seated at both ends.
- All flexible ducts must meet UL safety standards for Class I air ducts and connectors.
- All ducting must be installed according to HVAC codes and standards.
- For optimum performance, keep duct run as short and straight as possible.
- All duct connections should be sealed with UL181 foil tape or mastic to prevent leakage.
- Exterior intake hood must be weather resistant.
- Exterior intake hood must have a screen (1/4" openings) to prevent unwanted debris, animals, and insects from entering ductwork. A metal open hood model is recommended. An intake vent with plastic louvers significantly reduces airflow.
- Exterior intake hood should be above the expected snow line or a minimum of 18" above ground level, whichever is greater.
- Exterior intake hood should be a minimum of 10 ft. from appliance vents or other sources of pollution and/or extreme temperatures, such as furnace exhaust or car exhaust, etc.
Damper Installation
- Install damper with crimped end downstream.
- Slide damper over end of crimped duct and secure to duct with 1/2 inch long sheet metal screws (not included).
- Insulate the damper assembly. Leave the motor cover exposed for wiring.
NOTE: Support all duct work in accordance with local code or SMACNA standards.
NOTE: The damper blade, as supplied, is fully closed when not powered and will fully open when powered. The stop screw can be used to limit how much the damper opens when powered. The damper is 10 VA at 24 VAC power-opened/spring-closed.
Figure 4 - Aprilaire Damper
Diagram of the Aprilaire Damper showing BRACKET, MOTOR, INDICATOR LABEL, and ADJUSTABLE STOP SCREW.
Figure 5 - Damper Installation
Diagram showing the FRESH AIR INTAKE, ROUND DAMPER, and AIR FLOW DIRECTION. An arrow indicates 'DO NOT INSULATE ACTUATOR'.
Wiring
Disconnect power to HVAC equipment. Make wire connections as shown in Figure 6.
- Wire the 24VAC transformer (provided with Model 8126A only). The transformer should be continuously energized, do not wire to the HVAC blower circuit. The transformer, damper and the ventilation controller “VENT” terminals will be wired in series.
- Wire R, C, and W terminals on the ventilation controller to the corresponding terminals on the HVAC control board. Leaving any existing R, C, and W leads in place.
- Disconnect the thermostat wire from the HVAC terminal G and connect it to the ventilation controller G terminal.
- Wire Gf on the ventilation controller to the HVAC terminal G. The only wire connected to HVAC G will be from the ventilation controller Gf terminal.
Figure 6 - Wiring to Controller
Wiring diagram showing connections between the THERMOSTAT, FURNACE, DAMPER, 24 VAC TRANSFORMER, and the 8120A DIGITAL VENTILATION CONTROLLER TERMINAL STRIP. The terminal strip includes POWER (R, C, USED), INPUTS (ODT, W, G), and OUTPUTS (VENT, Gf).
Outdoor Temperature Sensor (ODT)
If selecting a mode with temperature limits (B, C or D), the outdoor temperature sensor must be installed.
Select Mounting Location for Outdoor Temperature Sensor (ODT)
The temperature sensor can be located in the fresh air duct, in the vent inlet, or on the outside of an exterior wall.
- Do not mount in direct sunlight.
- Do not mount closer than three feet to any exhaust vent.
- Do not route wire alongside 120VAC wires.
- Do not use more than 300 feet of wire to connect the sensor.
- Do not mount below the expected snow line on exterior walls.
Figure 7 - ODT Mounted Outside
Diagram shows an OUTDOOR TEMPERATURE SENSOR mounted on the exterior wall of a home (NORTH, EAST, OR WEST SIDE), above the expected snow line, with SENSOR BRACKET and SENSOR LEADS.
Figure 8 - ODT Mounted in Intake Duct
Diagram shows an OUTDOOR TEMPERATURE SENSOR mounted inside the FRESH AIR INTAKE DUCT, with a maximum length of 36 inches from the OUTSIDE WALL, aligned with the CENTER LINE.
Mode Selection
This controller is equipped with 4 mode settings. The “A” mode allows the controller ventilate based on time only. The "B", "C", and “D” modes allow the controller to ventilate based upon time, outdoor temp, and indoor humidity.
Mode A: Time Only
Timer controlled ventilation (No temperature or humidity limits). This setting can be calculated with ASHRAE 62.2-2010 standards. (Temperature and humidity sensors are ignored.)
Mode B: Default
Timer controlled ventilation with humidity and temperature limits. The chart displays ventilation zones based on OUTDOOR TEMPERATURE (F) and INDOOR RELATIVE HUMIDITY.
Mode C: Cold Climate
Timer controlled ventilation with humidity and temperature limits. The chart displays ventilation zones based on OUTDOOR TEMPERATURE (F) and INDOOR RELATIVE HUMIDITY.
Mode D: Warm Climate
Timer controlled ventilation with humidity and temperature limits. The chart displays ventilation zones based on OUTDOOR TEMPERATURE (F) and INDOOR RELATIVE HUMIDITY.
Determine Ventilation Requirements
Calculate Ventilation Time Requirements and Select Ventilation Time Setting
Step 1: Determine the minimum ventilation requirement.
This is calculated using ASHRAE 62.2-2010.
Airflow in CFM = [House Area in Sq Ft x 0.01] + [No. bedrooms +1 x 7.5] Use the Number of Bedrooms (Plus 1) or the Number of Occupants, whichever is larger.
| Home Size (ft²) | Number of Bedrooms | ||||
|---|---|---|---|---|---|
| < 2 | 2 - 3 | 4 - 5 | 6 - 7 | > 7 | |
| ≤ 1500 | 30 | 45 | 60 | 75 | 90 |
| 1501 - 3000 | 45 | 60 | 75 | 90 | 105 |
| 3001 - 4500 | 60 | 75 | 90 | 105 | 120 |
| 4501 - 6000 | 75 | 90 | 105 | 120 | 135 |
| 6001 - 7500 | 90 | 105 | 120 | 135 | 150 |
| > 7500 | 105 | 120 | 135 | 150 | 165 |
Additional ventilation may be required for pets, hobbies, fireplaces and attached garage, etc. If more outdoor air is required than the Ventilation Controller can deliver, increase delivered CFM by: reducing bends in duct, increasing duct size, adding a second duct, or adding a powered fan.
Indicate the required CFM: __________
Setting Ventilation Time
Step 2: Determine the ventilation controller fresh air delivery rate.
| Duct Length | Negative Static Pressure ("w.c.) as Measured for Return Duct or Plenum | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 0.05 | 0.1 | 0.15 | 0.2 | 0.25 | 0.3 | |||||||
| Flex | Pipe | Flex | Pipe | Flex | Pipe | Flex | Pipe | Flex | Pipe | Flex | Pipe | |
| 10 ft. | 60 | 65 | 85 | 90 | 105 | 110 | 120 | 125 | 135 | 140 | 150 | 160 |
| 20 ft. | 55 | 60 | 80 | 85 | 100 | 105 | 115 | 120 | 130 | 135 | 140 | 150 |
| 30 ft. | 50 | 55 | 75 | 80 | 95 | 100 | 110 | 115 | 125 | 130 | 130 | 140 |
Measure the negative static pressure of the return system and consult table above for approximate inlet airflow. These values are not absolute. An airflow measuring device (Nailor-Hart, etc.) will give the Ventilation Controller's airflow exactly.
For the table above, the flex duct is laid loose with 2 wide 90° bends, and the damper is full open. For the rigid pipe the values are based on two 90° elbows, and the damper is open. For both cases the air intake is through a metal vent hood with a bird screen. Adjust airflow up or down for variations, including elbows or bends, or if the length of duct you're using isn't listed, etc.
Measure the delivered airflow or determine from above chart and record __________
Step 3: Determine the ventilation controller knob setting.
| CFM Delivered | CFM Required | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 20 | 30 | 40 | 50 | 60 | 70 | 80 | 90 | 100 | 110 | 120 | ||
| 60 | 20 | 30 | 40 | 50 | 60 | 70 | 80 | 90 | 100 | 110 | 120 | |
| 80 | 15 | 25 | 30 | 40 | 45 | 55 | 60 | 70 | 75 | 85 | 90 | |
| 100 | 15 | 20 | 25 | 30 | 35 | 40 | 50 | 55 | 60 | 65 | 70 | |
| 120 | 10 | 15 | 20 | 25 | 30 | 35 | 40 | 45 | 50 | 55 | 60 | |
| 140 | 10 | 15 | 15 | 20 | 25 | 30 | 35 | 40 | 45 | 50 | 55 | |
| 160 | 10 | 10 | 15 | 20 | 25 | 25 | 30 | 35 | 40 | 45 | 50 | |
Use your entries from Steps 1 and 2 in the table above. From this you can determine the correct knob setting. For example, if 80 CFM is required, and the Vent delivers 120 CFM set the knob to 40 minutes.
If more outdoor air is required, increase delivered CFM by reducing bends in duct, increasing duct size, adding a second duct, or adding a powered fan.
System Checkout
- Turn the time setting knob to the TEST/RESET position. If the installation is correct the HVAC blower will turn on (independent of heat or cooling operation) and the damper will open for 1 minute unless the knob is turned off of TEST/RESET. If the system does not operate see the Troubleshooting Guide.
- Return the time setting knob to the calculated setting. Do not leave in TEST/RESET, the Ventilation Controller will not operate.
Troubleshooting
Technical support is available Monday through Friday, 7:00 a.m. to 5:00 p.m. CST, at 800-334-6011. Use the troubleshooting guide to identify and correct system faults. Contact technical support before replacing the controller or damper, and for additional troubleshooting.
| Symptom | Troubleshooting Procedure |
|---|---|
| HVAC Blower does not turn on in Test Mode. | 1. Make sure HVAC equipment has power. 2. Check the wiring for R, C, W and G and Gf at both the HVAC equipment and the Ventilation Controller. 3. Check voltage across the Ventilation Controller R&C and C&Gf terminals. Voltage should be in the 22 VAC to 30 VAC range. |
| Damper does not open in Test Mode. | 1. Follow steps 1-3 above. 2. Check wiring diagram to make sure the damper is wired in series with the circuit board and transformer. |
Table 4 - Troubleshooting Guide (continued)
| Symptom | Troubleshooting Procedure |
|---|---|
| The damper does not open with the blower operating. | 1. The damper will not operate once the ventilation time interval has been met. For example, if the knob is turned to 5 minutes and 5 minutes has elapsed, the damper will close and it will stay closed until the next 1-hour interval. For all modes except Mode A: 2. If the Indoor RH is above 55% and the outdoor temperature is above 50° the damper will not open because of the potential for excess humidity. 3. If the outdoor temperature is below 0° or above 100° the vent stays off. 4. Verify that the outdoor temperature sensor is located properly. See page 12. 5. Turbulence in the return duct, plenum or mixing box can give false readings. Confirm proper location. See pages 5-6. 6. In Mode B, a heat call is required for ventilation under 20°F. 7. In Mode D, a heat call is required for ventilation under 40°F. |
| Blower turns on unexpectedly. | If ventilation time has not been met, the controller will activate the blower. This is normal operation. |
Table 5 - Error Codes
| Displayed Error Code | Troubleshooting Procedure |
|---|---|
| Display Error Code: E1: RH Sensor | Rotate knob to the "Test/Reset" position. After 5 seconds, the green indicator will blink, resetting the error. If E1 returns, replace the controller. |
| Display Error Code: E2: Controller Knob | Rotate knob to the "Test/Reset" position. After 5 seconds, the green indicator will blink, resetting the error. If E2 returns, replace the controller. |
| Display Error Code: E3: Outdoor Temperature Sensor | 1. Make sure that the Outdoor Temperature Sensor is properly connected to the ODT terminals on the controller. 2. Measure the resistance of the ODT sensor by removing the wires from the terminals and measuring the resistance across the wires with an ohmmeter. Confirm the reading with the temperature in the table. If the resistance value does not match the temperature value, replace the ODT sensor. 3. Reset error by rotating knob to Test/Reset then back to the normal setting. Note: ODT must be installed for Mode B, C, and D. |
| Outdoor Temperature (°F) | Resistance (kΩ) ±10 |
|---|---|
| -30 | 231.8 |
| -20 | 163.4 |
| -10 | 117.3 |
| 0 | 84.8 |
| 10 | 62.2 |
| 20 | 46.1 |
| 30 | 34.4 |
| 40 | 26.1 |
| 50 | 19.9 |
| 60 | 15.3 |
| 70 | 11.9 |
| 80 | 9.3 |
| 90 | 7.3 |
| 100 | 5.8 |
