T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
147 60-24858
Fig. 128. Schematic and hookup of T874R with Q674L. Used in heat pump applications. Fig. 129. Schematic and hookup of T874G with Q674L. Used in heat pump applications.
FALL
AUTO
ON
H1
HEAT
OFF
COOL
L2
M5653A
POWER SUPPLY. PROVIDE
DISCONNECT MEANS AND
OVERLOAD PROTECTION
AS REQUIRED.
FAN
SWITCH
L1
(HOT)
SYSTEM
SWITCH
SYSTEM
MONITOR
1
1
R
W3
Y
B
L
W2
X
E
FAN RELAY
G
O
LACO CHP
COMPRESSOR
CONTACTOR
EM. HT. RELAY
COOL CHANGEOVER
VALVE
RD
EM. HT.
LED
(YELLOW)
AUX. HT.
LED
(GREEN)
H2
FALL
EM. HT.
RD
RTD1 EHR1
RTD2
ODT2
EHR2 RTD3
RTD1
H1/C1
ANTICIPATOR ODT1
A
SERVICE
LED (RED)
C1
H2 ANTICIPATOR
2
3
4
5
6
THERMOSTAT SUBBASE SYSTEM COMPONENTS
H1
FALL L1
(HOT)
L2 1
H2
FALL
CO
RISE
C1
RISE
H1 ANTICIPATOR
H2 ANTICIPATOR
C1
ANTICIPATOR
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
COMPRESSOR
CONTACTOR
M102A
COOL CHANGEOVER VALVE
EM. HT. RELAY AUX. HT. RELAY
FAN RELAY
G
R
W
X
EM. HT.
LED (RED)
B
O
Y
SYSTEM
SWITCH
EM. HT.
HEAT
OFF
COOL
FAN
SWITCH
AUTO
ON
2
3
4
6
8
9
10
1
THERMOSTAT SUBBASE SYSTEM COMPONENTS