Honeywell T874 - Page 195

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
195 60-2485—8
Fig. 203. Schematic and hookup of T874L with Q674C. Used in heat pump applications.
Fig. 204. Schematic and hookup of T874D with Q674F. Used in standard applications.
CO
FALL
Y
R
W
OFF
SYSTEM
SWITCH
C1 ANTICIPATOR
AUTO
ON
FAN SWITCH
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
M2981
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
4
6
8
9
10
H1
FALL
RISE
C1
H1 ANTICIPATOR
2
COMP.
FAULT
(RED)
AUTO
COMPRESSOR
CONTACTOR
L1
(HOT
)
L2
1
G
FAN RELAY
W2
HEAT CHANGEOVER
VALVE
A
COMPRESSOR
FAULT
3
H1
FALL
W1
G
W2
B
HEAT RELAY 1
HEAT
OFF
COOL
SYSTEM
SWITCH
H1 ANTICIPATOR
C1 ANTICIPATOR
AUTO
ON
FAN
SWITCH
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
LED IS NOT LABELED. JUMPER W2 TO X FOR AUXILIARY HEAT INDICATION. JUMPER E TO X FOR
EMERGENCY HEAT INDICATION. CONNECT SYSTEM MONITOR TO X TO IDENTIFY WHEN SYSTEM
NEEDS TO BE CHECKED.
M2982A
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
R
EM. HT. RELAY
COMPRESSOR
CONTACTOR 2
COMPRESSOR
CONTACTOR 1
1
4
6
8
9
10
11
H2
FALL
C2 ANTICIPATOR
RISE
RISE
C1
C2
Y1
Y2
HEAT RELAY 2
L1
(HO
T)
L2
1
2
LED
(RED)
H2
ANTICIPATOR
AUTO
EM. HT.
X
E
FAN RELAY