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How to read an HVAC ladder wiring diagram: a condensing unit example
A ladder diagram draws power as two vertical rails with each load on its own horizontal rung. The line-voltage section shows L1 and L2 feeding the compressor and condenser fan through the contactor contacts, with the run capacitor. The 24-volt section shows R from the transformer through the thermostat Y contact, the high-pressure and low-pressure switches in series, to the contactor coil and back to C. A legend shows the symbols for normally open and normally closed contacts, a coil, a pressure switch, a fuse, a capacitor, a motor and a transformer.
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