Lennox ELP Series User Manual page 18

COOLING
1 - Cooling demand energizes through terminal Y1 at
the indoor thermostat.
2 - Voltage passes through N.C. K8-1 to CMCI defrost
control.
3 - L1 reversing valve is energized.
4 - Voltage passes through N.C. low pressure switch
S87 and N.C. high pressure switch S4.
5 - Compressor contactor K1 is energized. N.O. K1-1
contacts close, energizing compressor B1.
6 - K1-1 closes energizing compressor B1 on low
speed and K10-1 closes energizing outdoor fan B4
and B5 in ELS120S. K1-2 opens to de-energize
crankcase heater HR1.
7 - On two speed systems, voltage passes through
K67-1, energizes
switching compressor to high speed.
SEQUENCE OF OPERATION – ELP 90 / 120
compressor solenoid
1 - Heating demand energizes through terminal W1 at
the indoor thermostat.
2 - K8 transfer relay is energized. N.C. K8-1 contacts
open and N.O. K8-2 contacts close, sending voltage
to CMCI defrost control.
3 - L1 reversing valve is de-energized.
4 - K10 outdoor fan relay is energized. N.O. K10-1
contacts close, energizing outdoor fans B4 and B5,
N.C.
5 - Compressor contactor K1 is energized. N.O. K1-1
contacts close, energizing compressor B1.K1-2
opens to de-energize crankcase heater HR1.
During heating operation, when outdoor coil drops below
42º F, the defrost thermostat closes. If defrost thermostat
L34,
remains closed at the end of 30, 60, or 90 minutes, defrost
control energizes and defrost begins.
When defrost control energizes, reversing valve L1 and
indoor heat relay are energized. Outdoor fan is deener-
gized.
Defrost continues until 14 ± 1 minutes have elapsed or un-
til defrost pressure switch opens. When defrost pressure
switch opens to terminate defrost, the defrost timer loses
power and resets. Defrost timing is stopped until the next
call for defrost (when defrost thermostat closes).
Page 18
HEATING
DEFROST MODE