Lennox ComfortSense L7742U Programming And Application Manual page 35

Figure 16. Dual Fuel Flowchart
LEGEND
HBSP − High Balance Set Point
LBSP − Low Balance Set Point
ODT − Outdoor Temperature
NOTES
LBSP and HBSP must not be set closer than 2ºF
2nd stage lock in temperature −20ºF to 75ºF (OFF)
Temperature Operation
Heat Pump Heat Only
HBSP
Heat Pump or Gas/Oil Heat
LBSP
Gas/Oil Heat Only
ODT NO
< LBSP − 3
YES
?
NO
NO
ODT
< LBSP − 3
?
YES
NO
De−energize
Y1 or Y1&Y2,
and G
A
YES YES
YES
NO Upstage
2nd stage
timer expired
demand
?
?
ODT
YES NO
< HBSP − 3 or
(if HBSP is
OFF)
?
YES YES
NO Upstage
3rd stage
timer expired
demand
?
?
Indoor heat
YES
heat (non−HP)
demand (W1) or EM
heat demand
ODT above
Compress-
or speed 1 (Y1
YES
De−energize
Y1, Y2, G
lock in temp
Energize Y1, B, Stg1
G and start
NO
upstage timer
Indoor heat
demand
?
NO
YES
Indoor heat
demand
?
Page 35 ComfortSenset Model L7742U Touch Screen 7−Day Programmable Thermostat
START
NO
demand
?
Gas/oil
YES
?
NO
LBSP +3
NO
?
A
YES
2nd stg
W1
only) ?
HP (Y2) or
Gas (W1)
NO ?
Y2
ODT
> stg2 (Y2)
NO
?
YES
HP
Stg2
Energize Y1, Y2,
stage
B, G and start
demand
upstage timer
?
De−energize
W1 and W2
HEAT PUMP
LOCKOUT
Energize 1st
stage gas/oil heat
(W1) and start
upstage timer
Indoor heat
demand
NO
?
YES
Upstage timer
expired
YES
?
NO
4th
stage demand
or 2nd stage gas/oil
NO
demand (W2)
?
YES
Energize W2
YES
NO
Indoor heat
demand
?