Lennox CHA16, Руководство по обслуживанию

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Page 63
CHA162553, 2753, 3003 Operation Sequence: B41 Section and C1
Sections
(Basic Unit with Basic Electromechanical Thermostat)
Blower Operation:
1- Blower demand from thermostat terminal G energizes pilot relay K46.
2- N.O. K461 closes energizing blower contactor K3 and energizes the econo
mizer (If installed). Outdoor damper drives to minimum position.
3- N.O. K31 closes, blower begins operation.
1st Stage Cooling:
4- Cooling demand energizes Y1 and G in the thermostat. G energizes
blower (see step 1).
5- After a delay from DL8 (30 second on delay, 240 second off delay), Y1 ener
gizes pilot relay K66 after passing through N.C. Freezstat S49, N.C. High
Pressure limit S4 and Loss of Charge Switch S24.
6- N.O. K661 closes and 24VAC energizes Fan Start Relay K127and
Compressor Contactor K1 after passing through N.C. compressor moni
tor switch S3.
7- K11 closes energizing compressor.
8- K1271 closes energizing Condenser Fan contactor K10.
9- N.O. K101 closes energizing condenser fan motor B4.
2nd Stage Cooling:
10- After a delay from DL9 (30 second on delay, 240 second off delay), sec
ond stage cooling demand Y2 is routed through N.C freezstat S50, high
pressure limit S7 and low pressure limit S25 energizing pilot relay K67.
11- N.O. contacts K671 close energizing Compressor Contactor K2 and
Condenser Fan 2 Contactor K68.
12- N.O. contacts K21 close energizing compressor B2.
13- N.O. contacts K681 close energizing condenser fan motor 2 (B5).
1st Stage Heating: (See CHA161853 with Electric Heat Pages 5657)
14- Heating demand energizes W1 in the thermostat. Pilot relay K77 is
energized.
15- N.O. K771 close energizing electric heat stage 1 The operation se
quence 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)
16- Additional heating demand energizes W2 in the thermostat. Pilot relay
K49 is energized.
17- N.O. K491 close energizing electric heat stage. The operation se
quence of electric heat units varies depending on size (kW input rating)
and line voltage rating.
Safety Blower Operation:
18- If either limits in the electric heat section trip, the heating elements are im
mediately deenergized.
19- The indoor blower remains energized powered by K3 which is ener
gized by thermostat demand.