Learn What HVAC Contactors Are and How They Help Your System

HVAC contactors provide critical central air-conditioner components with the higher voltage they need to produce cool air for your home. While many parts of the central AC utilize standard low-voltage power, the system compressor and the fan that circulates air through the condenser coil require 220- or 240-volt electricity to do the job.

How HVAC Contactors Get Cooling Started

HVAC contactors are a type of spring-loaded switch that actuates when signaled by the system thermostat. In standby mode between cycles, the contactor switch is open and no current is supplied to the critical components. When the indoor thermostat senses that cooling is required in the house, it signals the contactors which, in turn, actuate to switch on high-voltage electricity that energizes the specified components and initiates the cooling process.

When the thermostat senses that the indoor temperature has reached the desired setting, the unit signals the contactors to disconnect power from the high-voltage components, terminating the cooling cycle. During the standby period, other parts in the air conditioner remain powered with standard low-voltage electricity.

Issues That May Affect Contactors

Contactors are moving parts exposed to heat and mechanical wear. After years of use, contactors may become unreliable or fail entirely.  It is not unusual to need contactor replacement in older central air conditioners. Symptoms associated with worn contactors include:

• A chattering noise emanating from inside the outdoor AC unit every time the system starts up.
• A loud humming sound inside the unit, followed by the air conditioner failing to cycle on.
• The air conditioner continues to run and does not respond to the thermostat signal to shut down at the end of the cooling cycle.

Stay Safe

High-voltage electrical power present in the outdoor AC unit makes work on these components hazardous for anyone other than a trained technician. For safety’s sake, leave the repair/replacement of contactors to a qualified, professional HVAC contractor.

For more information about problems with HVAC contactors as well as certified, experienced technicians to resolve these issues, talk to the professionals at Energy 1 Heating & Air Conditioning.