Lennox CHA16 - CHA16-1853 Operation Sequence: B9 Section and C1 Sections; (Basic Unit with Basic Electromechanical Thermostat)

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CHA161853 Operation Sequence: B9 Section and C1 Sections
(Basic Unit with Basic Electromechanical Thermostat)
Blower Operation:
1- Blower demand from thermostat terminal G energizes pilot relay K46. N.O.
K461 closes energizing blower contactor K3. K32 energizes the economiz
er (If installed). Outdoor damper drives to minimum position.
2- N.O. K31 closes, blower begins operation.
1st Stage Cooling:
3- Cooling demand energizes Y1 and G in the thermostat. G energizes
blower (see step 1).
4- After a delay from DL8 (30 second on delay, 240 second off delay), Y1 ener
gizes pilot relay K66.
5- N.O. K661 closes. 24VAC power energizes outdoor fan relay K10 and
Time Delay DL15. In 30 seconds compressor two will begin operation
(see step 8). The unit is equipped with three compressors. Two com
pressors operate in the first stage of cooling.
6- 24VAC power energizes outdoor fan relay K10.
7- N.O. K101 closes energizing condenser fan motors B4 and B5.
8- 24VAC power is routed through N.C. low discharge temp. sensor S3, N.C.
freezstat S49, N.C. high pressure limit S4 and N.C. low pressure limit S24 to
energize compressor contactor K1.
9- N.O. Contacts K1-1 close energizing compressor B1.
10- Time delay DL15 closes in 30 seconds from initial first stage thermostat de
mand. 24VAC power is routed through N.C. freezstat S50, N.C. high pres
sure limit S7 and N.C. loss of charge switch S25 energizing compressor
contactor K2.
11- N.O. Contacts K21 close energizing compressor B2.
2nd Stage Cooling:
12- Second stage cooling demand energizes Y2.
13- After a delay from DL9 (30 second on delay, 240 second off delay), Y2 ener
gizes pilot relay K67.
14- N.O. K671 closes.
15- 24VAC power is routed through N.C. freezstat S53, N.C. high pressure limit
S28 and N.C. loss of charge switch S34 to energize compressor contactor
K14.
16- N.O. K141 closes energizing compressor 3 (second stage.)
1st Stage Heating: (See CHA161853 with Electric Heat Pages 5657)
17- Heating demand energizes W1 in the thermostat. Pilot relay K77 is
energized.
18- N.O. K771 close energizing electric heat stage 1 The operation sequence of
electric heat units varies depending on size (kW input rating) and line voltage
rating.
2nd Stage Heating (If equipped with multiple stage heating):
(See CHA161853 with Electric Heat Pages 5657)
19- Additional heating demand energizes W2 in the thermostat. Pilot relay
K49 is energized.
20- N.O. K491 close energizing electric heat stage . The operation sequence of
electric heat units varies depending on size (kW input rating) and line voltage
rating.
Safety Blower Operation:
21- If either limits in the electric heat section trip, the heating elements are
immediately deenergized.
22- The indoor blower remains energized, powered by K3 which is ener
gized by thermostat demand.