Contactor
Contactor turns up in 2 fields: electrotechnology, HVAC. Here is what it means to the people in each one.
Contactor in electrotechnology
An electrically controlled switch used for switching an electrical power circuit.
A heavy-duty relay designed to repeatedly open and close high-current power circuits. Unlike a standard control relay, a contactor is built with arc suppression mechanisms and robust contacts to handle the heavy inrush currents of electric motors, lighting banks, or heating loads. It is typically controlled by a lower voltage circuit, allowing a small switch or PLC to safely command a massive load.
"The main pump won't start because the coil on the motor contactor has burned out."
Contactor in HVAC
A heavy-duty relay that uses a 24 volt control signal to switch line voltage to a compressor and condenser fan.
When the thermostat calls, the contactor coil pulls in and closes its contacts. Contacts pit and burn over time, and a contactor that welds shut runs the outdoor unit nonstop, while one with chattering contacts damages the compressor. Ants and other insects drawn to the electrical field are a famous cause of jammed contacts in warm climates.
"Contactor's pitted black and buzzing, swap it while you're up here, it's a ten dollar part that saves a compressor."