Honeywell T874 - Page 155

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
155 60-2485—8
Fig. 140. Schematic and hookup of T874W with Q674L. Used in heat pump applications.
1
T
W3
U
G
R
E
L
X
B
O
Y1
Y2
C815A OD THERMISTOR
AUX. HT. RELAY
FAN RELAY
EM. HT. RELAY
COMPRESSOR
MONITOR
HEAT CHANGEOVER
RELAY
COOL CHANGEOVER
RELAY
COMPRESSOR
CONTACTOR 1
COMPRESSOR
CONTACTOR 2
EM.HT.
AUTO
ON
FAN SWITCH
H1 ANTICIPATOR
H2 ANTICIPATOR
H3 ANTICIPATOR
RESET
FALL
FALL
FALL
H1
H3
H2
AUX. HT.
LED
(GREEN)
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
CONNECT CHANGEOVER RELAY TO 'O' TERMINAL FOR CHANGEOVER IN COOLING OR TO 'B' TERMINAL FOR CHANGEOVER IN HEATING.
M156A
C1 ANTICIPATOR
RISE
RISE
C2 ANTICIPATOR
C1
C2
EM. HT.
LED (RED)
CHECK LED
(RED)
HEAT
OFF
COOL
SYSTEM
SWITCH
2
2
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
1
2
3
4
5
6
8
9
10
11
12
L1
(HOT)
L2
1