Lennox CHA16 - B2 diagram with C1 diagram CHA16-1603 Operating Sequence; CHA16-1603 Operation Sequence: B2 Section and C1 Sections; (Basic Unit with Basic Electromechanical Thermostat)

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B2 diagram
with C1 diagram
CHA16-1603 Operating Sequence
CHA161603 Operation Sequence: B2 Section and C1 Sections
(Basic Unit with Basic Electromechanical Thermostat)
Blower Operation:
1- Blower demand from thermostat terminal G energizes blower contactor K3.
2- N.O. K31 closes, blower begins operation. N.O. K32 closes energizing economizer damper motor
(if economizer is installed, outdoor damper drives to minimum position).
1st Stage Cooling (Low Ambient Kit Installed):
3- Cooling demand energizes Y1 and G in the thermostat. G energizes blower (see step 1.)
4- 24VAC power energizes low ambient relay K128.
5- N.O. K1281 closes energizing outdoor fan relay K10.
6- N.O. K101,2 close energizing condenser fan motors B4 and B5.
7- N.O. K103 closes. 24VAC power is routed around N.C. low discharge temp. sensor S3, through
N.C. freezstat S49, N.C. high pressure limit S4 and N.C. low pressure limit S24 to energize com
pressor contactor K1.
8- N.O. Contacts K1-1 close energizing compressor B1.
1st Stage Cooling (Low Ambient Kit Not Installed):
9- Cooling demand energizes Y1 and G in the thermostat. G energizes blower (see step 1.)
10- 24VAC power energizes outdoor fan relay K10.
11- N.O. K101,2 close energizing condenser fan motors B4 and B5.
12- N.O. K103 closes. 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.
13- N.O. Contacts K1-1 close energizing compressor B1.
2nd Stage Cooling (With Low Ambient Kit):
14- Second stage cooling demand energizes Y2. 24VAC power is routed through N.C freezstat S50,
around N.C. low discharge temp. sensor S30, through high pressure limit S7 and low pressure limit
S25 energizing compressor contactor K2.
15- N.O. contacts K21 close energizing compressor B2.
2nd Stage Cooling (With Out Low Ambient Kit):
16- Second stage cooling demand energizes Y2. 24VAC power is routed through N.C freezstat S50,
through N.C. low discharge temp. sensor S30, through high pressure limit S7 and low pressure
limit S25 energizing compressor contactor K2.
17- N.O. contacts K21 close energizing compressor B2.
1st Stage Heating: (See CHA161853 with Electric Heat Pages 5657)
18- Heating demand energizes W1 in the thermostat. 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. The operation sequence of electric
heat units varies depending on size (kW input rating) and line voltage rating.
Safety Blower Operation:
20- If either limits in the electric heat section trip, the heating elements are immediately deen
ergized.
21- Indoor blower remains energized powered by K3 energized by thermostat demand.