A contactor is defined as an electrical relay that is used to control the flow of current in a circuit. Many people also call it relief. In reality, a relay is defined as a device that responds to small changes in current or voltage by activating a switch or other device in a circuit.
In the real world of heating and air conditioning, this means that contactors can handle higher currents than relays. Relays are generally reserved for small pilot tasks. Most heating and air conditioning service technicians do not refer to a contactor as a relay. Read more about what an AC contactor is and how it works by browsing the internet.
A typical unipolar or bipolar contactor is found in modern homes with a split gas stove with air conditioning or heat pump. A single-pole has only one set of contacts, while the bipolar has two.
In reality, the contactor has at least two separate circuits. (Some commercial contactors have multiple circuits.) One circuit is a low voltage coil circuit and the other is a charging circuit.
The coil circuit in most AC or heat pump systems uses a 24-volt coil, but there are some systems that use a 230-volt coil in conjunction with a small relay that turns the contactor on and off. This 230-volt winding system is mostly found in older systems or commercial units these days. Before replacing the contactor, make sure the correct coil voltage is used or the coil could burn out.
The coil voltage is indicated on the small plate on the side of the contactor. The 230-volt main current coming from the main house power supply is routed through the contacts in the contactor next to the main when the coil is powered by a call from the house or system refrigeration thermostat cooling Heat pump or heater.