Bryant T874 Thermostat User Manual


 
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
19 60-24858
Fig. 22. Tracing the emergency heat and EM. HT. LED circuit.
Fig. 23. Tracing the cooling circuit.
M5844
L1
(HOT)
L2
1
LACO
CHP
Y
B
E
O
G
L
X
W2
W3
R
ODT 1
RTD 1 EHR 1
RTD 2
ODT 2
EHR 2 RTD 3
RD
SYSTEM
MONITOR
FAN RELAY
COMPRESSOR
CONTACTOR
CHANGEOVER
VALVE
EM. HT.
RELAY
RTD 1
AUX. HT.
LED
(GREEN)
EM. HT.
LED (RED)
FAN SWITCH
ON
AUTO
SYSTEM
SWITCH
EM. HT.
HEAT
OFF
COOL
H2
FALL
H1
FALL
C1
2
3
4
5
6
H1/C1
ANTICIPATOR
H2
ANTICIPATOR
1
POWER SUPPLY. PROVIDE
DISCONNECT MEANS AND
OVERLOAD PROTECTION
AS REQUIRED.
THERMOSTAT SUBBASE
SYSTEM COMPONENTS
M5845
L1
(HOT)
L2
1
LACO
CHP
Y
B
E
O
G
L
X
W2
W3
R
ODT 1
RTD 1 EHR 1
RTD 2
ODT 2
EHR 2 RTD 3
RD
SYSTEM
MONITOR
FAN RELAY
COMPRESSOR
CONTACTOR
CHANGEOVER
VALVE
EM. HT.
RELAY
AUX. HT.
LED
(GREEN)
EM. HT.
LED (RED)
FAN SWITCH
ON
AUTO
SYSTEM
SWITCH
EM. HT.
HEAT
OFF
COOL
H2
FALL
H1
FALL
C1
2
3
4
5
6
H1/C1
ANTICIPATOR
H2
ANTICIPATOR
1
POWER SUPPLY. PROVIDE
DISCONNECT MEANS AND
OVERLOAD PROTECTION
AS REQUIRED.
THERMOSTAT SUBBASE
SYSTEM COMPONENTS
RTD 1