Aprilaire 8120 Setup guide

Model 8120A & 8126A
Digital Ventilation Controller
READ AND SAVE THESE INSTRUCTIONS
Safety &
Installation
Instructions

2 3
Safety Instructions................................................................................3
Specifications....................................................................................4
Overview .......................................................................................4
Mounting Location................................................................................5
Mounting Controller...............................................................................7
Ductwork & Damper Installation.....................................................................9
Wiring.........................................................................................11
Mode Selection .................................................................................13
Determine Ventilation Requirements ................................................................15
Setting Ventilation Time ..........................................................................17
System Checkout ................................................................................18
Troubleshooting .................................................................................19
TABLE OF CONTENTS 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.

4 5
SPECIFICATIONS OVERVIEW
Operating temperature range 20-160°F
Maximum current through VENT relay 2A
Input voltage 22-30 VAC
Minimum VA required 2.0 VA
The ventilation controller will bring in fresh air
and activate 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 (see Figures 1 & 2).
VENTILATION CONTROLLER
AIR FLOW
(RETURN)
FILTER FURNACE/AIR HANDLER
FRESH AIR
INTAKE HOOD
W/SCREEN
FRESH AIR
INTAKE DUCT
MOTORIZED
DAMPER
FRESH AIR
GABLE END WALL,
BAND JOIST, OR PORCH SOFFIT
SUPPLY
PLENUM
6”
90-948
FIGURE 1 – Typical Attic Installation

6 7
MOUNTING LOCATION
OUTSIDE
WALL
FRESH AIR
FRESH AIR
INTAKE DUCT
MOTORIZED
DAMPER
VENTILATION
CONTROLLER
AIR
FLOW
FURNACE/AIR HANDLER
FILTER
FRESH AIR
INTAKE HOOD
W/SCREEN
RETURN DUCT SUPPLY
DUCT
HUMIDIFIER
6”
90-948
FIGURE 2 – Typical Basement Installation
MOUNTING CONTROLLER
DISASSEMBLE THE CONTROLLER MOUNT CONTROLLER TO DUCT
Remove the knob. Remove the cover by pulling at the
bottom and swinging out and up.
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.

8 9
3/4" DIA HOLE
MOUNTING CONTROLLER
90-1830
FIGURE 3 – Fiber and Sheet Metal Duct Mount
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
1. Sharp edges may cause
serious injury from cuts. Use
care when cutting openings
and handling duct work.
2. Install damper in fresh air duct
as close to the return duct as
possible.
3. 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.

10 11
INDICATOR LABEL
BRACKET
MOTOR
ADJUSTABLE
STOP SCREW
90-935
(shown with plastic cover removed)
DUCTWORK & DAMPER INSTALLATION
DAMPER INSTALLATION
Step 1: Install damper with crimped end downstream.
Step 2: Slide damper over end of crimped duct and
secure to duct with 1/2 inch long sheet metal
screws (not included).
Step 3: 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.
ROUND
DAMPER
FRESH AIR INTAKE
AIR FLOW
DIRECTION DO NOT INSULATE
ACTUATOR
FIGURE 4 – Aprilaire Damper
FIGURE 5 – Damper Installation
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.
90-1829
FIGURE 6 – Wiring to Controller
CONTINUOUSLY POWERED
24 VAC TRANSFORMER
G
Y
W
C
R
THERMOSTAT
OUTPUTSINPUTSPOWER
GW
CR VENT ODTGf
120 VAC
R
C
W
Y
G
FURNACE
USED
NOT
8120A DIGITAL VENTILATION CONTROLLER TERMINAL STRIP
DAMPER

12 13
WIRING
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.
If selecting a mode with temperature limits
(B, C or D), the outdoor temperature sensor must
be installed. NORTH, EAST
OR WEST SIDE
OF HOME
OUTDOOR
TEMPERATURE
SENSOR
SENSOR
BRACKET
SENSOR
ABOVE EXPECTED
SNOW LINE
OUTDOOR
TEMPERATURE
SENSOR LEADS
FIGURE 7 – ODT Mounted Outside
FIGURE 8 – ODT Mounted in Intake Duct
CENTER LINE
OUTSIDE WALL
36" MAX.
MODE SELECTION
Position Description Chart
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.)
B
(Default)
Timer controlled
ventilation with
humidity and
temperature limits
VENTILATION
PREVENTED
VENTILATION ALLOWED
VENTILATION ALLOWED WITH HEAT
100°
20°
0°
55%
INDOOR RELATIVE HUMIDITY
OUTDOOR TEMPERATURE (F)
50°
VENTILATION PREVENTED
15% 25% 35% 45
%6
5%
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.

14 15
MODE SELECTION
Position Description Chart
C
(Cold Climate)
Timer controlled
ventilation with
humidity and
temperature limits
VENTILATION
PREVENTED
VENTILATION ALLOWED
100°
0°
55%
INDOOR RELATIVE HUMIDITY
OUTDOOR TEMPERATURE (F)
50°
VENTILATION PREVENTED
15% 25% 35% 45
%6
5%
D
(Warm Climate)
Timer controlled
ventilation with
humidity and
temperature limits
VENTILATION
PREVENTED
VENTILATION ALLOWED
VENTILATION ALLOWED WITH HEAT
0°
55%
INDOOR RELATIVE HUMIDITY
OUTDOOR TEMPERATURE (F)
50°
40°
VENTILATION PREVENTED
15% 25% 35% 45
%6
5%
90°
DETERMINE VENTILATION REQUIREMENTS
CALCULATE VENTILATION TIME REQUIREMENTS AND SELECT VENTILATION TIME SETTING
TABLE 1 – Ventilation Air Requirements, CFM
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
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.
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 __________

16 17
DETERMINE VENTILATION REQUIREMENTS
2. Determine the ventilation controller fresh air delivery rate.
TABLE 2 – CFM Delivered
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 __________
SETTING VENTILATION TIME
3. Determine the ventilation controller knob setting.
TABLE 3 – Cycle Time Setting (minutes) for Airflow Delivered vs. Airflow Required for 1 Hour Cycle
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.

18 19
SYSTEM CHECKOUT
1. 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.
2. 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.
TABLE 4 – Troubleshooting Guide
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.

20 21
TROUBLESHOOTING TROUBLESHOOTING
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
(k ) ±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

22 23

P.O. Box 1467 • Madison, WI 53701-1467 • Phone: [phone] • Fax: [phone]
www.aprilairepartners.com
10010003 11.12
B2205858A © 2012 Aprilaire – A division of Research Products Corporation