Honeywell T8424D Installation Instructions

T8424D ELECTRONIC MULTISTAGE THERMOSTAT
3 69-1386-1
Fig. 4. Wiring connections.
Fig. 5. Typical hookup of T8424 in two-stage heat and
two-stage cool system with manual changeover.
Mounting Thermostat to Wallplate
1. Engage the tabs at the top of the thermostat and
wallplate.
2. Swing down the thermostat and press the lower
edge of the thermostat onto the wallplate to latch.
See Fig. 6.
OPERATION
Setting FAN and SYSTEM Switches
Fan and system settings are controlled manually by
using the switches located at the bottom of the
thermostat case. See Fig. 7.
Fig. 6. Mounting thermostat wallplate.
FAN Switch
Fan switch settings are:
On: The fan runs continuously. Use for improved air
circulation and air quality.
Auto: Normal setting for most homes. In cooling, the
fan starts and stops with the cooling equipment. In
heating, the fan is controlled directly by the heating
equipment and may start a few minutes after the
heating equipment turns on (on most systems).
When using an electric heat thermostat, the fan
starts and stops with the heating equipment.
Slide the FAN switch in the bottom left corner of the
thermostat to select the desired fan setting.
SYSTEM Switch
System switch settings control thermostat operation as
follows:
Cool: The thermostat controls the cooling system.
Off: Both heating and cooling are off.
Heat: The thermostat controls the heating system.
Slide the SYSTEM switch in the bottom right corner of
the thermostat to select the desired system setting.
TERMINAL
SCREW
M20212
G
R
C
Y
W1
B
O
FOR STRAIGHT
INSERTION STRIP
5/16 IN. (8 MM)
FOR WRAPAROUND
STRIP 7/16 IN. (11 MM)
Y2
W2
L1
(HOT)
L2
1
1
W2
Y
G
R
C
1ST STAGE
COOLING
2ND STAGE
COOLING
FAN
RELAY
STAGE-TWO
HEATING
Y2
24V
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND
OVERLOAD PROTECTION AS REQUIRED.
M20213
T8424
W1
STAGE-ONE
HEATING
M14677
S
YSTEM
Cool O
ff Heat
A
u
to
O
n
F
A
N
DASHED LINES INDICATE TABS
ON BACK OF THERMOSTAT
S
Y
S
T
E
M
Cool Off Heat
A
u
to
O
n
F
A
N
ENGAGE TABS AT TOP OF THERMOSTAT
WITH SLOTS ON MOUNTING PLATE.
PRESS LOWER EDGE OF
CASE TO LATCH.
A
B

Honeywell T8424D Specifications

General

Brand	Honeywell
Model	T8424D
Category	Thermostat
Language	English