Honeywell T874 - Page 194

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
60-2485—8 194
Fig. 201. Schematic and hookup of T874R with Q674L. Used in heat pump applications.
Fig. 202. Schematic and hookup of T874D with Q674G. Used in standard applications.
T
G
R
Z
X
W1
FAN RELAY
EM. HEAT
OFF
SYSTEM
SWITCH
AUTO
ON
FAN SWITCH
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
M2979
COMPRESSOR
CONTACTOR
SERVICE
1
3
6
11
L1
(HOT
)
L2
1
2
SERVICE
LED
(YELLOW)
Y
EM. HT.
LED (RED)
COOL
HEAT
W2
OUTDOOR
THERMOSTAT
SEQ 2
K
SEQ 1
HEAT CHANGEOVER
VALVE
H2
ANTICIPATOR
RISE
H2
H1
C1
RISE
4
5
C1 ANTICIPATOR
12
H1 ANTICIPATOR
RESET
THERMOSTAT
SUBBASE SYSTEM COMPONENTS
C815A
OUTDOOR
THERMISTOR
OUTDOOR
THERMOSTAT
H1
FALL
W1
W2
T
RC
RH
O
FAN RELAY B
HEAT RELAY 1
AUTO
OFF
SYSTEM
SWITCH
H1 ANTICIPATOR
C1 ANTICIPATOR
NO
FAN
SWITCH
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED
M2980
THERMOSTAT
SUBBASE SYSTEM COMPONENTS
L1
(HOT
)
L2
1
COMPRESSOR
CONTACTOR 2
COMPRESSOR
CONTACTOR 1
1
4
6
7
9
10
12
H2
FALL
C2 ANTICIPATOR
RISE
RISE
C1
C2
Y1
Y2
HEAT RELAY 2
L1
(HOT
)
L2
1
H2
ANTICIPATOR
A2
"T" RELAY
B
FAN RELAY O
A1
5
8
11
SERVICE
LED (RED)
SERVICE
LED (RED)