Honeywell T874 - Page 189

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
189 60-2485—8
Fig. 191. Schematic and hookup of T874R with Q674B. Used in heat pump applications.
Fig. 192. Schematic and hookup of T874D with Q674C. Used in standard applications.
L2
1
OFF
H1/C1
ANTICIPATOR
H1
FALL
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
M3965
Z
H2
W2
HEAT
2
4
6
FALL
AUX. HT. RELAY
"Z" RELAY
L1
(HOT
)
R
FAN RELAY
Y
AUTO
CONT.
FAN
SWITCH
C
G
H2
ANTICIPATOR
3
COOL
RELAY
COOL
THERMOSTAT SUBBASE SYSTEM COMPONENTS
SYSTEM
SWITCH
C1
LO
HI
O
W1
HEAT RELAY
COOL CHANGE-
OVER VALVE
L2
1
ON
H1
ANTICIPATOR
H1
FALL
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS
AND OVERLOAD PROTECTION AS REQUIRED.
MOMENTARY POSITION. SPRING RETURN TO "ON" UPON SWITCH RELEASE.
M3959
C1
Y1
H2
RISE
W1
C1
ANTICIPATOR
C2
RISE
AUTO
1
4
6
8
9
10
COMPRESSOR
CONTACTOR 2
FALL
HEAT RELAY 1
Y2
11
C2
ANTICIPATOR
W2
HEAT RELAY 2
COMPRESSOR
CONTACTOR 1
L1
(HOT
)
R
FAN RELAY
O
AUTO
OFF
SERVICE
LED (RED)
FILTER
LED
(YELLOW)
X
A
G
O
2
2
MOMENTARY
CIRCUIT
H2
ANTICIPATOR
THERMOSTAT SUBBASE SYSTEM COMPONENTS
FAN
SWITCH
SYSTEM
SWITCH