Lennox LCM Series - Page 58

Page 58
Sequence of Operation LGM/LCM210, 240U, 300U
1- Line voltage from TB13 energizes transformer T1 and T18. Transformer T1 and T18 provides 24VAC power to
the main controller A55. The transformers also provide 24VAC power to the unit cooling, heating and blow
er controls and thermostat.
ECONOMIZER OPERATION
2- The A55 Unit Controller receives a demand and energizes exhaust fan relay K65 and K231 with 24VAC at 50%
(travel) outside air damper open (adjustable).
3- N.O. K65‐1, K65‐2, K231-01 and K231-02 close, energizing exhaust fan motors B10 and B11.
1ST STAGE COOLING
4- First stage cooling demand energizes Y1 and G in the thermostat.
5- 24VAC is routed to the A55 Unit Controller. After A55 proves N.C. low pressure switch S87, and S88 and N.C. high
pressure switch S4 and S7, high temperature limits S5 compressor contactors K1 and K2 are energized.
6- N.O. contacts K1-1 and K2-1 close energizing compressor B1 and B2. Crankcase heater HR 2 is de-energized.
7- A55 energizeS outdoor fans B4, B5 and B21. A178 energizes outdoor fan B22, B23 and B24.
8- Relay K191 opens de-energizing compressor 1 crankcase heater HR1
2ND STAGE COOLING
9- Second stage cooling demand energizes Y2.
10- N.O. contacts K14-1 close energizing compressor B13, de-energizing HR5.
11- N.O. contacts K146-1 close energizing compressor B20, de-energizing HR11.
BLOWER OPERATION With By Pass
1- Control inverter A96 energizes contactor K202 and main control A55 energizes relay 203.
2-
K203-1 N.C. contacts open to de-energize K3 relay coil. K3 contacts open to interrupt power to B3
blower motor through K3 N.O. relay contacts.
3- K202 contacts close to allow power to B3 blower motor from A96.
BLOWER OPERATION No By-Pass
1- Control inverter A96 energizes B3 on a G demand.