Honeywell T874 Product Data page 138

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
THERMOSTAT
H1
FALL
H1 ANTICIPATOR
H2 ANTICIPATOR
H2
FALL
C1
RISE
C1 ANTICIPATOR
C2 ANTICIPATOR
C2
RISE
1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
2 OPTIONAL ECONOMIZER HOOKUP (DOTTED LINES).
Fig. 117. Schematic and hookup of T874D with Q674L. Used in heat pump applications.
60-2485—8
SUBBASE
2
FAN
SWITCH
3
AUTO
4
ON
5
6
8
10
SYSTEM
SWITCH
EM. HT.
11
HEAT
OFF
COOL
R
ENTHALPY
CONTROL RELAY
B
HEAT RELAY
CONTACT 1
G
ECONOMIZER
RELAY
ENTHALPY
CONTROL
2
ENTHALPY
CONTROL
RELAY 2
Y1
ENTHALPY
CONTROL
RELAY 1
TIME DELAY
Y2
DEFROST
RELAY
W
LED
(GREEN)
X
SERVICE
L
SERVICE
LED (RED)
O
138
SYSTEM COMPONENTS
L1
(HOT)
DEFROST
RELAY
L2
1
MOTOR
3
DEFROST
SWITCH
OUTDOOR
FAN RELAY 1
DEFROST SWITCH
RELAY
TM1
LOW AMBIENT
THERMOSTAT 1
OUTDOOR
OUTDOOR
FAN RELAY 3
FAN RELAY 2
1ST STAGE LOW
PRESSURE LIMIT
1ST STAGE
SHORT
CYCLE
CONTROL
TIME DELAY
HEATER
2ND STAGE
SHORT
CYCLE
2ND STAGE LOW
CONTROL
PRESSURE LIMIT
HEAT
RELAY 1
OUTDOOR
THERMOSTAT
DEFROST
RELAY
COOL CHANGEOVER
VALVE
TM2
MOTOR
1
MOTOR
2
M7755