Honeywell T874 - Page 198

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
60-2485—8 198
Fig. 209. Schematic and hookup of T874R with Q674L. Used in heat pump applications.
Fig. 210. Schematic and hookup of T874Y with Q674E. Used in heat pump applications.
L
EM. HEAT
OFF
SYSTEM
SWITCH
AUTO
ON
FAN SWITCH
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
3
6
2
AUX. HT.
LED
(GREEN)
Y
EM. HT.
LED (RED)
COOL
HEAT
H2 ANTICIPATOR
RISE
H2
H1
C1
FALL
4
H1/C1
ANTICIPATOR
G
W2
B
R
EM. HT. RELAY
COOL
CHANGEOVER
VALVE
COMPRESSOR
CONTACTOR
’"B" RELAY
EM. HT.
RELAY
L1
(HOT
)
L2
1
X
E
FAN RELAY
AUX. HT. RELAY
O
M2987
H1
FALL
G
B
HEAT
OFF
COOL
SYSTEM
SWITCH
H1 ANTICIPATOR
C1 ANTICIPATOR
AUTO
ON
FAN
SWITCH
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
M2988
THERMOSTAT
SUBBASE SYSTEM COMPONENTS
R
COMPRESSOR
CONTACTOR 2
COMPRESSOR
CONTACTOR 1
1
3
6
8
9
10
11
H2
FALL
C2 ANTICIPATOR
RISE
RISE
C1
C2
Y1
Y2
L1
(HO
T)
L2
1
FILTER
LED
(YELLOW)
H2
ANTICIPATOR
AUTO
FAN RELAY
HCO
FALL
CCO
2
4
O
L
F
COOL
CHANGEOVER
VALVE
HEAT
CHANGEOVER
VALVE
RESET
LED
(RED)