Aprilaire 8400 Installation Manual
8400 Series Thermostats
Safety &
Installation
Instructions
READ AND SAVE THESE INSTRUCTIONS
TABLE OF CONTENTS
INSTALLATION
INSTALLATION
Installation location recommendations................................................................3
Outdoor temperature sensor (optional) ................................................................4
Thermostat mounting..............................................................................5
Power & reset options.............................................................................5
Wiring terminal ..................................................................................6
Wiring diagrams .................................................................................7
SETUP & TESTING
System setup instructions .........................................................................11
System test mode ...............................................................................16
REFERENCES
Quick reference to controls & display
• Non-programmable models (8444, 8446, 8448).....................................................22
• Programmable models (8463, 8465, 8466).........................................................23
Thermostat features .............................................................................24
Troubleshooting .................................................................................25
Specifications...................................................................................27
2 3
INSTALLATION LOCATION RECOMMENDATIONS
Thermostat should be mounted:
• On an interior wall, in a frequently occupied space.
• Approximately 5‘ above floor.
• At least 18” from outside wall.
• Thermostat can be mounted to a vertical junction box.
Do not mount thermostat:
• Behind doors, in corners, or other dead air spaces.
• In direct sunlight, near lighting fixtures, or other
appliances that give off heat.
• On an outside or unconditioned area wall.
• In the flow of a supply register, in stairwells, or near
outside doors.
• On a wall with concealed pipes or ductwork.
INSTALLATION
INSTALLATION
OUTDOOR TEMPERATURE SENSOR (OPTIONAL)
Outdoor temperature can be measured by attaching an
8052 sensor to the S1 and S2 terminals. System setting
#05 (Remote sensor) is used to enable sensor.
Heat pump models can use the outdoor temperature to
effectively utilize the heat pump:
• When the outdoor temperature is less than the Low
Balance Point, the heat pump will be locked out and
only auxiliary heating will be used.
• When the outdoor temperature is higher than the High
Balance Point, the auxiliary heating will be locked out
and only the heat pump will be used to provide heating.
• Install on side of building out of direct sunlight
(north side recommended).
• Mount above snow line.
• Mount at least 3’ away from exhaust vents and
condensing lines.
• Maximum wire length is 300’.
• Do not route wires along 120 VAC lines.
THERMOSTAT MOUNTING
1. Remove the back of the thermostat, by pressing the
tab on the bottom of the unit.
POWER & RESET OPTIONS
The thermostat is dual power. It can either be AC or
battery powered, or both (to provide backup power for
the clock). Batteries are optional if the thermostat was
connected to AC power when installed.
For heat pump models (8446 and 8465) and universal
models (8448 and 8466) used in heat pump applications
24 VAC must be connected in order for the system fault
and emergency heat indicators to operate.
The thermostat has a memory backup that saves the
thermostat’s settings in case of a power interruption.
The reset button located under the battery cover can be
used to reset the thermostat back to factory defaults.
The system settings will also be reset back to defaults.
2. Pull wires through the opening on the back of the
thermostat.
3. Position and level the back of the thermostat on wall
and mark the hole locations with a pencil.
4. Drill 1/4” holes and insert supplied anchors (drywall only).
G
S1
C
W
RC
4 5
Y
R
S2
O/B
Y2
L
W2
5. Place back over anchors, insert and tighten screws.
6. Seal wire entry holes to prevent drafts affecting
temperature readings.
INSTALLATION
C
G
Y
W
R
S1
S2
RC
TRANSFORMER
C
G
Y
W
R
S1
S2
RC
COOLING
INSTALLATION
WIRING TERMINAL
Wire specifications
18-24 gauge thermostat wire
Installation notes
• Ensure power at the HVAC equipment is off.
• Loosen screw terminals, insert stripped wire
and re-tighten.
• Push the excess wire back into the opening
and plug the wall opening to prevent drafts.
RC – 24 VAC supply cooling*
R – 24 VAC supply heating*
W – 1st stage heat / auxiliary
Y – 1st stage cooling / compressor
G – Fan
C – RC 24VAC common (optional when powered by batteries)
S1 & S2 – outdoor temperature sensor (optional)
O/B – Reversing valve
L – System fault indicator
W2 – 2nd stage heat / auxiliary
Y2 – 2nd stage cooling / compressor
* Jumper between RC & R is used in single transformer systems
G
C
(see wiring diagrams).
S1
S2
O/B
L
W2
Y2
W
RC
6 7
Y
R
WIRING – MODEL 8463 & 8444 SINGLE
TRANSFORMER (USE JUMPER WIRE)
FAN
HEATING
COOLING
JUMPER
SENSOR
OUTDOOR TEMP
WIRING – MODEL 8463 & 8444 TWO
TRANSFORMERS (REMOVE JUMPER WIRE)
HEATING
TRANSFORMER
TRANSFORMER
HEATING
FAN
COOLING
SENSOR
OUTDOOR TEMP
INSTALLATION
TRANSFORMER
C
G
Y
W
R
L
S1
S2
O/B
RC
HEAT PUMP
C
G
Y
W
R
L
S1
S2
O/B
RC
TRANSFORMER
C
G
Y
W
R
L
S1
S2
O/B
W2
Y2
RC
HEATING
COOLING
C
G
Y
W
R
L
S1
S2
O/B
W2
Y2
RC
INSTALLATION
WIRING – MODEL 8465 & 8446 SINGLE
TRANSFORMER (USE JUMPER WIRE)
AUX HEATING
JUMPER
FAN
COMPRESSOR
SENSOR
OUTDOOR TEMP
REVERSE VALVE
FAULT DETECT
WIRING – MODEL 8465 & 8446 TWO
TRANSFORMERS (REMOVE JUMPER WIRE)
AUX HEATING
TRANSFORMER
TRANSFORMER
AUX HEATING
COMPRESSOR
FAN
SENSOR
OUTDOOR TEMP
REVERSE VALVE
FAULT DETECT
WIRING – MODEL 8466 & 8448 SINGLE
TRANSFORMER (USE JUMPER WIRE)
FOR HEAT/COOL SYSTEM
JUMPER
1st HEATING
1st COOLING
FAN
SENSOR
OUTDOOR TEMP
NOT USED
2nd HEATING
NOT USED
WIRING – MODEL 8466 & 8448 TWO
TRANSFORMERS (REMOVE JUMPER WIRE)
FOR HEAT/COOL SYSTEM
TRANSFORMER
FAN
2nd COOLING
TRANSFORMER
1st HEATING
1st COOLING
SENSOR
OUTDOOR TEMP
NOT USED
NOT USED
8 9
2nd HEATING
2nd COOLING
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