T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
189 60-24858
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
1POWER 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
1POWER 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)
RFAN 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