Simply stated, a contactor is an “ON/OFF” switch for an air conditioner or heat pump; the unit located outside your home or business. When it becomes too warm or too cold, the thermostat sends a 24 volt current to the contactor and the outside unit comes on. When the desired temperature is reached, the thermostat stops sending the 24 volt current and the unit shuts off.
Here’s how it works?
Two high voltage wires power your outside unit. Under normal conditions, power is supplied continuously. These power wires are connected to your contactor, which breaks, or interrupts the flow of electricity to the system components (Compressor & condenser fan motor). Wires on both sides of the contactor are connected by a spring-loaded metal strip or strips. When the thermostat calls for the unit to come on, a current travels through two low voltage wires to a coil at the base of the contactor and creates an electro-magnetic force pulling the metal strip down and bridging the gap between the two sets of wires. Think of a draw-bridge being lowered to allow traffic to cross a river. When the thermostat is satisfied, the room temperature is where it should be, the electro-magnetic force stops and the spring pushes the metal strip(s) away from the wires, breaking power to the unit (the bridge is up).
Looking at the picture, the high voltage wires are on the bottom and the top. The smaller wires on the sides supply low voltage power to the coil, which is at the base of the contactor (not visible in picture). The metal strip, the part that is raised or lowered, is on the front-right side. This contactor only breaks one of the two high voltage wires, others break both. To learn more about how your AC works, call the Orlando, FL air conditioning experts at Downtown Air and Heat.
