Why Does My AC Make a Loud Noise When It Turns On?
Whether you recently had an air conditioning installation in Brisbane done or have had your system for years, you may have noticed that your air conditioner makes a loud noise when you first turn it on. This startup noise is a common occurrence that even experienced air conditioning companies in Brisbane can't always prevent.
In this blog post, we'll explore some of the most common reasons your AC unit may be making loud noises upon startup and what you and your local air conditioning installation technicians in Brisbane can do about it.
The Compressor is Kicking On
The main component in an air conditioner that is responsible for cooling is the compressor. When you first turn on the AC, the compressor has to kick on from a stopped state. This initial startup requires a burst of power and causes mechanical stresses on the compressor's motor and components.
As the compressor motor engages, you'll often hear a loud humming, grinding or whooshing sound as it struggles to get up to speed. Some compressors also have hard start kits installed which further increase the initial electrical load to help the compressor turn over. This loud startup noise is completely normal and should only last a few seconds before quieting down.
Refrigerant Flow Noise
Another common cause of loud startup noise is refrigerant's sudden movement and flow through the AC system's pipes and components. When the compressor first engages, it has to work to get refrigerant moving through the evaporator coil, condenser coil, expansion valve and other parts of the refrigeration loop.
As the refrigerant changes state from liquid to gas and back again, you'll often hear it rushing and swooshing through the pipes, especially at the outdoor condenser unit. This refrigerant flow noise is also temporary and should dissipate within 30 seconds to a minute after startup.
Fan Motor Noise
The indoor blower fan and outdoor condenser fan motors must also start moving air when the AC is powered on. Like the compressor motor, the initial fan motor startup requires more electrical current and causes mechanical stresses.
You may hear the fan motor winding up with a whirring or grinding sound until it reaches full speed. Fan motor bearings that are getting old or worn can exacerbate this loud startup noise problem. The noise should fade out within a minute once steady-state operation is achieved.
Other Potential Causes of Loud AC Startup Noise
While the compressor, refrigerant flow and fan motors account for the vast majority of loud startup noise cases, there are a few other less common issues that could be the culprit:
Loose or Vibrating Components: Loose fan blades, fan guards or panels vibrating against the unit housing can sometimes cause rattling noises on startup.
Refrigerant Low or Dirty Coils: Low refrigerant charge or dirty/clogged evaporator and condenser coils increase system resistance and workload, leading to louder operation.
Worn Compressor Bearings: Older compressors with worn bearings may grind or squeal louder during initial engagement.
Improper Installation: Issues like improper refrigerant line sizing, incorrect air flow or ductwork connections can overload the system at startup.
When Loud Noise Persists After Startup
In most cases, loud AC startup noise is completely normal and only lasts a few seconds as the system reaches steady operating speed and pressure. However, if the noise persists for more than a minute after turning it on, it's a sign that further troubleshooting may be needed.
Some potential issues to investigate if loud noise carries on include:
Low Refrigerant: A low refrigerant charge can cause the compressor to labour excessively on startup. Check system pressures.
Worn Compressor: An older compressor may be nearing the end of its lifespan if grinding/squealing persists after warmup.
Loose Components: Check for any loose, vibrating or rubbing parts that could be rattling continuously.
Dirty Coils: Excessively dirty evaporator and condenser coils increase airflow resistance across the whole system.
Fan/Blower Issues: Issues like a seized or unbalanced fan motor/blade could cause prolonged high noise.
When to Call an HVAC Pro
For the occasional loud startup that only lasts a few seconds, no action may be needed since it's considered normal operation. However, if noise issues persist beyond a minute or two of running, it's best to contact an HVAC technician for an inspection and diagnosis.
A pro can check refrigerant levels, examine components for wear/damage, clean coils if needed, and diagnose more serious mechanical or installation issues. They have the training and equipment to properly service air conditioners and resolve noise problems before more expensive repairs are required down the road.
Reducing Loud Startup Noise
While brief loud startup noise may not be avoidable with most AC units, here are some tips that may help reduce the intensity:
Ensure Proper Airflow/Ductwork: Correct sizing and installation improve system efficiency at startup.
Clean Outdoor Coil Regularly: Dirty coils increase backpressure and compressor workload on startup.
Lubricate Moving Parts Annually: Keeping fan motors, bearings and linkages lubricated smooths operation.
Upgrade to Variable Speed Components: Newer variable speed compressors and ECM motors start and run more quietly.
Install Sound Insulation: Adding acoustic insulation to the outdoor unit can help muffle startup noise transmission.
With proper maintenance and addressing any issues causing prolonged noise, homeowners can keep their AC operating as quietly as possible, even during initial startup when some noise is unavoidable. Let me know if you have any other air conditioner questions!