Lennox CHA16, Руководство по обслуживанию

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Page 68
B1 diagram with C1 diagram
CHA16-823 / 953 Operating Sequence
CHA16823, 953 Operation Sequence: B1 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. K31 closes, blower begins operation. N.O. K32 closes energizing economizer damper
motor (if economizer is installed, outdoor damper drives to minimum position).
1st Stage Cooling (both compressors B1 and B2 operate separately):
3- Cooling demand energizes Y1 and G in the thermostat. G energizes blower (see step 1.) Y1
energizes condenser contactor K10. N.O. K101 closes energizing condenser fan B4.
4- N.O. K102 closes enabling second stage compressor contactor K2.
5- 24VAC power is routed through compressor monitor S3, N.C. freezstat S49, N.C. high pres
sure limit S4 and N.C. low pressure limit S24 to energize compressor contactor K1.
6- N.O. Contacts K1-1 close, compressor B1 begins operation.
2nd Stage Cooling:
7- Second stage cooling demand energizes Y2. 24VAC power is routed through high pressure limit S7
and low pressure limit S25 energizing compressor contactor K2.
8- N.O. contacts K21 close energizing compressor B2. B2 begins operation.
1st Stage Heating: (See CHA161853 with Electric Heat Pages 5657)
9- 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 CHA161853 with Electric Heat Pages 5657)
10- 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:
11- If limits in the electric heat section trip, heating elements are immediately deenergized.
12- I indoor blower remains energized powered by K3 energized by thermostat demand.