Because your central air conditioner requires high-voltage electricity for certain functions, HVAC contactors are the components that get the job done. While certain parts in the system run on low voltage, other internal components require 220- or 240-volt electricity to start up and run when the unit cycles on.
How a Contactor Kick-Starts Your AC
A contactor is basically a spring-loaded, heavy-duty automatic switch which keeps high-voltage electricity flowing to the component as long as required. While the air conditioner is in standby mode between cooling cycles, only standard voltage components in the unit remain energized. When the thermostat sends a signal to initiate cooling, however, contactors react by switching high voltage to two major components: the system compressor and the condenser coil fan, both installed in the outdoor housing of the central AC.
Once the desired indoor temperature has been achieved, the thermostat signals the HVAC contactors to disconnect power to the compressor and the coil fan, terminating the cooling cycle and leaving only the standard voltage components in the unit powered up.
When Good HVAC Contactors Go Bad
As small mechanical devices that integrate moving parts and which are exposed to heat, a central AC contactor is subject to wear and tear over the typical lifespan of an air conditioner. If you own a central AC long enough, replacement of worn contactors will likely be necessary at some point. Here are some signs that a contactor is failing:
- A noticeable chattering sound emanating from the outdoor central AC unit every time the unit cycles on.
- Loud humming coming from the outdoor unit. The system fails to cycle on and cool air is not produced.
- The outdoor unit does not respond to the thermostat signal and continues to run nonstop even after the programmed temperature setting has been achieved.
Don’t Do It Yourself
The high-voltage electricity that contactors are connected to presents a serious safety hazard. Leave diagnosis and replacement of contactors to certified HVAC technicians only.
For experienced, professional service to repair issues involving HVAC contactors, contact Ace Hardware Home Services.
