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LENNOX
HP16, HP19, HP21, HP22 (DIRECT REPLACEMENTS)
Existing
Function
Terminals
Common
X
Power
V VR
Compressor
M
1st Stage
–
Heat
Auxiliary
Y
Heat
Fan
F
C/O Valve
–
Heat
C/O Valve
R
Cool
System Monitor/
L
Sytem Defrost
Outdoor Stat/
E
Em. Heat
Outdoor
A
Sensor
LED Indication
–
Terminal B (C or X) must be connected to transformer common.
Tape off. Thermostat replaces outdoor reset with improved zero droop
performance.
Do not remove factory-installed jumper.
Optional LED indication activated with completed circuit on X1 and X2
terminals.
L terminal is powered continuously when thermostat is in Em. Ht. position.
TYPICAL THERMOSTATS AND SUBBASES — HONEYWELL MODEL NUMBER (CUSTOMER PART NUMBER)
T874C1448/Q674L1355 (24F5101/31F3201)
T874R1178/Q674L1355 (24F5601/31F3201)
70-6627 • 80
Electromechanical
B
B
B
R
R
R
Y
Y
Y
–
–
–
W
W
W
G
G
G
–
–
–
O
O
O
F
F
F
X2
X2
X2
T
T
T
–
–
–
Electronic Replacement or Upgrade
®
Chronotherm
III
C
C
R
R
or
Y1
Y
Y
W1
W1
W2
W2
G
G
B
B
O
O
O
L
L
E
E
X1 X2
–
If separate transformers are used, replace with one 75 Va transformer as
shown on page 78.
R8222B1067 Relay required to operate system monitor light (emergency
heat LED) on TRADELINE replacement thermostats. See page 11. Tape
off if LED indication is not desired.
Configure O/B (select models) in Installer Setup.
When W2 is not used, configure W2 cycle rate to NC.
LED is energized when terminal is powered.
T874C1448/Q674L1165 (24F5101/24F5901)
T874R1178/Q674L1165 (24F5601/24F5901)
Chronotherm
IV
C
C
C
R
R
R
Y1
Y
Y1
W1
W1
W1
W2
W2
W2
G
G
G
or
or
B
O/B
B
B
or
or
O/B
O
O
L
L
L
E
E
E
–
–
X1 X2
C
R
Y1/W1
–
Aux.
G
O/B
O/B
O/B
O/B
L
E
–
M13164
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