Wiring Diagrams - Lennox SignatureS
tat 81M26 Programming And Application Manual

Figure 7 shows a Dual Fuel Flowchart for 81M28 Thermostat.
Indoor
tstat heat
demand NO
?
YES
2nd stage
YES
heat demand
?
NO
De−energize
Outdoor
temp above
NO
LBP
?
YES
Gas heat lock-
out (when set for
aux heat = add
(comp = off))
De−energize Energize
Y1 & G Y1, B & G
2nd stage
heat demand
YES
?
NO
De−energize
W2
Indoor
tstat heat
YES demand
?
NO
Figure 7
505232 06/07
Dual Fuel Flowchart
for 81M28 Thermostat
Abbreviations:
aux = auxiliary
comp = compressor
LBP = Low Balance Point
temp = temperature
tstat = thermostat
Heat pump lockout
(when set for aux heat =
add (comp = off))
Y1
De−energize
Energize
W2
W2
Indoor
tstat heat
demand
NO
?
YES
2nd stage
heat demand
?
YES
NO
Outdoor
temp above
YES
LBP
?
NO

Wiring Diagrams

including dual fuel, zone control, and applications that include the Humidi-
®
trol accessory. See figures 8 and 9.
Typical Condensing Unit/Humiditrol
RED
PUR
BLK
FAN
RELAY
YEL
BLU
BLK
BRN
Y1 Y2 JUMPER − IN FOR
SINGLE− STAGE COOLING;
OUTDOOR
REMOVED FOR 2−STAGE
UNIT
COOLING
NOTES −
/1\ NOT REQUIRED FOR APPLICATIONS WITHOUT LSOM
/2\ NOT REQUIRED WITH SINGLE-SPEED OUTDOOR FAN)
/3\ NOT REQUIRED FOR SINGLE STAGE
/4\ ON 81M28 MODEL, E/W1 AND W2 TERMINALS MUST BE JUMPERED
TOGETHER FOR MOST APPLICATIONS
Page 26
Thermostat wiring connections with various units,
®
Accessory
Wiring Diagram
OUTDOOR SENSOR (46M98)
TWISTED PAIR
RED
BLK
PUR
EDA UNIT
INDOOR
UNIT
Figure 8
SignatureStat
t
THERMOSTAT