Wiring Diagrams And Sequence Of Operations - Lennox T?CLASS TPA024S4 Unit Information

Wiring Diagrams and Sequence of Operations27

M Voltage 380/420v (3PH) 50Hz
COOLING:
Internal thermostat wiring energizes terminal O by cooling mode selection, energizing the reversing valve L1.
1. Demand initiates at Y1 in the thermostat.
2. Assuming high pressure switch S4 and low pressure switch S87 are closed, 24VAC energizes compressor contactor
K1.
3. K1-1 N.O. closes, energizing compressor (B1) and outdoor fan motor (B4).
END OF COOLING DEMAND:
4. Demand is satisfied. Terminal Y1 is de-energized.
5. Compressor contactor K1 is de-energized.
6. K1-1 opens and compressor (B1) and outdoor fan motor (B4) are de-energized and stop immediately.
FIRST STAGE HEAT:
Internal thermostat wiring de−energizes terminal O by heating mode selection, de−energizing the reversing valve L1.
See steps 1, 2 and 3.
END OF FIRST STAGE HEAT:
See steps 4, 5 and 6.
DEFROST MODE:
During heating operation when outdoor coil temperature drops below 35°F (2°C) or 42°F (5.5°C)defrost switch (thermostat)
S6 closes.
1. Defrost control defrost control board begins timing. If defrost thermostat (S6) remains closed at the end of the 30,60
or 90 minute period, defrost relay energizes and defrost begins.
2. During defrost defrost control board energizes the reversing valve and W1 on the terminal strip (operating indoor unit
on the first stage heat mode), while de-energizing outdoor fan motor B4.
3. Defrost continues 14 + 1 minutes or until thermostat switch (S6) opens. When defrost thermostat opens, defrost control
timer loses power and resets.
4. When defrost control board resets, the reversing valve and W1 on the terminal strip are de-energized, while the outdoor
fan motor B4 is energized.
5. When defrost control board resets, the reversing valve and W1 on the terminal strip are de-energized, while the outdoor
fan motor B4 is energized.
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