Mounting The Thermostat - Honeywell T874G Installation Instructions Manual

THERMOSTAT
H1
C1
FALL
H2
FALL
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
1
2 TERMINAL LABELED C/X ON SOME MODELS.
3 W3 TERMINAL AVAILABLE ON SOME MODELS ONLY.
Fig. 10. Internal schematic and typical wiring diagram for T874R/Q674L in heat pump system. Includes EM. HT.

Mounting the Thermostat

Remove the thermostat cover by pulling the bottom
edge of the cover outward and away from the base
until it snaps free of the retaining posts.
NOTE: The cover is hinged at the top and must be
removed by pulling the bottom edge
outward and away from the base.
Carefully remove and discard the polystyrene
packing insert that protects the mercury switches
during shipment.
T874G,R MULTISTAGE HEAT PUMP THERMOSTATS AND Q674F,J,L SUBBASES
2
H1/C1
ANTICIPATOR
FAN
3 SWITCH
AUTO
ON
4
H2
ANTICIPATOR
6
SUBBASE
SYSTEM
SWITCH
EM. HT.
HEAT
OFF
COOL
and AUX. HT. LEDs.
Turn over the thermostat base and note the spring
fingers that engage the subbase contacts. Make
sure the spring fingers are
proper electrical contact with the subbase.
Note the tabs along the top inside edge of the
thermostat base. The tabs fit into the corresponding
slots on the top of the subbase. Mount the
thermostat on the subbase.
Align the two captive mounting screws in the
thermostat base with the posts on the subbase. See
Fig. 14. Tighten both screws.
screws
9
SYSTEM COMPONENTS
R
L
EM. HT.
LED (RED)
AUX. HT.
3 RELAY
W3
2
X
AUX. HT.
AUX. HT.
LED (GRN)
RELAY
W2
FAN RELAY
G
COOL CHANGEOVER
VALVE
O
E
EM. HT. RELAY
Y
COMPRESSOR
CONTACTOR
B
"B" RELAY
not
Do not overtighten
or damage to subbase can result.
L1
(HOT)
L2
1
M3683A
bent flat, preventing
69-0268—11