Sometimes our cars, appliances, and even air conditioners make the strangest noises, but how do you know if they’re normal or if something might be wrong? It’s not always as easy as hitting the ‘restart’ button on your computer, so it’s important to know when you should call a professional or contractor to check it out. The following are some tips about what sounds are normal and what indicates professional problem when it comes to your air conditioning unit. Outdoor unit noise is normal upon start-up and shut down.  The outdoor unit is where most of the mechanical operations in your system take place and depending on the type of equipment, it can be noisy and somewhat varied when it starts up and/or shuts down.  Typically, most air conditioners make noise when they first cycle on, which can be caused by the buildup of pressure in the refrigerant lines or from bearings, fans or other moving pieces starting up.  The same is true when the unit cycles off, or comes to a stop, as the pressures need to equalize.   

Sometimes this causes a unique noise that sounds like air escaping, a click or rattle. : If the start-up and shut down sounds are the same from cycle to cycle and not too loud, it’s probably normal and not worth calling a contractor. Outdoor unit running noise after start-up can also vary among different types of equipment.  Once the outdoor unit starts up, it should reach a consistent sound where you hear the fan blowing and the other mechanical parts humming along.  Sometimes you might hear a cycling sound over the period of a few seconds where the unit changes the pitch of its normal running sound and might get louder or quieter in “waves.”  If it gets increasingly louder as the system is running, then it might require a contractor to see whether it is out of balance or requires further inspection.  If you hear a loud, intermittent mechanical “scraping” or “banging” noise, this is not normal and you should shut your system down and call a contractor to inspect it as soon as possible.

: Significant changes in pitch or ‘banging’ noises indicate you should call a contractor. Indoor unit sound is usually the sound of the fan moving air through your system.  It is most noticeable when the system turns on and off. cost of installing a new ac unitIf you have a high efficiency system (16 SEER and over) you could hear two distinct sounds as your system moves from high to low cooling speed.  cover for ac wall unitThe high speed sound can be noticeable, but the low might be so quiet you can barely hear it.ac window unit 14 inches wide : Air moving through your system should sound smooth and consistent once it is running. In general, sound is a subjective attribute and the above descriptions are provided as a guideline for noises that could potentially signal a costly problem. 

In addition, we have recorded some typical compressor sounds you might hear during a normal start up, run and shut down cycle as examples. Sounds like the ones you will hear in this audio file are typical examples of what you might hear during normal operation in a healthy system. HVAC Glossary of TermsAir Conditioner Controllers have evolved to become more advance in tandem with the advancement made in the field of microcomputer. These days, most window air conditioner and room air conditioner in your homes or offices have electronic controllers in them that make the units more user friendly, intelligent and feature-rich. See some of the typical air conditioner controllers functions or some slight variation depending on the manufacturers of your unit. The compressor is the most important component of a vapor compression refrigeration system. The ON/OFF type of compressor used to be popular in the past but DC Inverter type of compressor is the latest technology in the market though more costly.

The ON/OFF compressor will totally ON or totally OFF depending on the set temperature and the ambient temperature. Usually there is a dead band of about 1.5 °C to 2.0 °C to prevent ON-OFF cycling of compressor that will reduce its lifespan. In cooling mode, the compressor will turn ON when the ambient temperature of the room is higher than the set temperature by 0.75°C (different manufacturer will have different value). It will only go off when the room temperature drops below 1.25 °C (different manufacturer will have different value). An example of the operation of a compressor in cooling mode. The disadvantage of this type of compressor is that the temperature range of the space being cooled is too big causing discomfort to the occupants during the time the compressor is either ON or OFF. The other disadvantage is the starting current of easily few times of the steady state current every time the compressor starts.Control Of AC/DC Inverter CompressorThe DC Inverter or AC Inverter type of control (obviously the compressor will also be of DC or AC Inverter type) has better control in that it does not have to turn off totally.

The frequency of the rotation of the compressor can vary depending on the load required. Hence the room temperature of the space being cooled can be very close to the set temperature most of the time with some slight variation.This type of air conditioner controllers provides a more comfortable cooling to the occupants as the temperature is constant most of the time. It is also more energy efficient and environmental friendly as most of the refrigerant used is ozone-friendly. The disadvantage is this type of unit is higher cost compared to the ON/OFF type. The mode setting button at the remote control usually enables you to set the mode of operation. It  can be set to COOL mode, HEAT mode (if your unit is a heat pump unit), DRY mode, AUTO mode or FAN mode. Look at the manual provided to see the symbols of each mode.COOL mode is the default setting that you will use if you want to cool the room upon entering it. The air conditioner will regulate the temperature to achieve the setting temperature of your remote control.

A temperature setting of 24 C° is a good setting to save energy. HEAT mode is the mode that you will use when you need to heat up the room during winter. In this mode, the evaporator effectively becomes a condenser and vice versa by using a reversing valve to reverse the flow of the refrigerant. A temperature setting of 28 C° is a good setting to save energy.In heat pump model, AUTO mode is a mode that will automatically change the mode between COOL and HEAT by sensing the temperature in the room. If the room temperature is low, HEAT mode will operate and if it goes up to a certain temperature, it will switch to COOL mode.In air conditioning model and depending on the manufacturer, the AUTO mode is actually operating in COOL mode but with a lower set temperature to cool down the room quickly before reverting to the set temperature of the user.DRY mode is a variation of COOL mode where the compressor will cycle on and off (or low speed if inverter model) for a few minutes each depending on the temperature of the room.

By this cycling, the moisture will be removed from the room hence the humidity of the room will drop. This is basically a dehumidifying function.FAN mode exists in some model. This mode is hardly used as there is no cooling effect to the room. Only the indoor fan is on. Most air conditioner controllers have the built-in economy or sleep mode function. This function is used when one is going to sleep. When activated using the remote control, the air conditioner unit will raise the set temperature in steps after a period of time. This is because the required cooling will reduce when one sleeps.Depending on manufacturer, the set temperature could increase by 1 °C after 1 hour of operation, 1.5 °C after 1.5 hours of operation and 2.0 °C after 2 hours of operation. Use this mode to save energy.Usually the fan speed can be change to Low, Medium, High or Auto. The Auto mode has a built-in intelligent that determine the speed of the fan depending on the room temperature and set temperature.

Higher speed is used if the difference between these two temperature is high and lower if low.Most unit will also have timers that you can use to ON or OFF the unit based on the clock of the remote control. Some simpler unit does not have clock but has delay timers that allow you to set the number of hours elapsed before the unit is turn ON or OFF.The auto random restart is a feature that will retain the settings of the controls in the event of a power failure. Once power is restored, the air conditioner will restart to its last settings with the compressor being powered up randomly. This is a good feature to look out for before you purchase the unit.Ionizer is now a basic feature in most room air conditioner unit. It is located at the indoor unit and has a high voltage electronic module that ionized the surrounding air with negative ions. These ions will attract dust and other contaminants from the return air to ensure that only fresh and clean air is discharged from the fan coil unit.

Take note that the module will have to be changed after a certain hours of operation to ensure its continuous efficiency.Air louver function helps to direct the air flow in the direction of your choice. Most controls have a least up and down control of the air. Some units may have left and right louver control as well.See the troubleshooting guide of the printed circuit board of a split unit.Learn how this thermostat can be used to discharge hot air during winter and cool air during summer.See the wiring color code of a typical thermostat.See the electronic symbols that represent the various components that are used to control the air conditioning systems.Use the 7 Day Programmable Thermostat to schedule your air conditioner and save energy at the same time. Types of HVAC ThermostatBasic descriptions on the types of thermostat that are usually used in HVAC. See the simplified block diagram of the split air conditioner using the latest DC inverter technology.This is another networking technology that you can use to link up all your equipment.