There are two sides to the average home A/C unit. You have the evaporator side or indoor blower and the condenser side outdoor unit. On a close of the thermostat 24v from r to y (G) the indoor fan relay closes(24v GC). Allowing 110v to the indoor blower. The 24v signal also travels to the condensing unit (YC). If equipped with low and/or high pressure switches and they are closed 24v will be supplied to the cooling contactor. When the cooling contactor coil is powered 220v will pass through the contactor to the compressor and condenser fan (Condenser fan sometimes have fan cycling controls). Both compressor and condenser fans have capacitors. Indoor blower motor typically 110v supplied to indoor unit through breaker Outdoor unit typically 220v supplied through separate breaker. Indoor unit transformer takes 110v and down steps to 24v for control power. (Sometimes internally fused) Typical 24v wiring C- Common leg of 24v R- Red supply side of 24v W- Heat Y- Cooling G- Indoor Fan
