How your air conditioning unit works:Your air conditioner is designed to automatically remove unwanted heat from your home. Understanding and caring for your unit ensures a longer life, maximum efficiency and saves repair or replacement costs.
Basic split system units are comprised of an evaporator coil, a condensing unit, and refrigerant lines. These parts work with the fan and control system in the air handler to cool your home.
The cooling cycle starts when the thermostat senses that the home’s air temperature is above the thermostat set point. Contacts in the thermostat are closed and control voltage (24 vac) is supplied to the air handler control board. This causes the blower on the air handler to start.
The air handler control board then supplies control voltage to the outdoor part of the system, called the condensing unit. This control voltage causes a device called a contactor to close its contacts. This supplies power to a fan and to a pump that is referred to as a compressor.
This pump raises the pressure and temperature of the refrigerant gas in the system. This high temperature and high pressure refrigerant passes through the outdoor coil. This coil (called the condenser coil) works the same way as the radiator on a car but it uses refrigerant instead of water. In the condenser, this high pressure refrigerant is cooled and condenses from a gas to a liquid. It is usually cooled to a temperature about 20 degrees below the saturation temperature and is called sub cooling.
This high pressure/low temperature liquid refrigerant is pumped to the indoor section of the system. Then the refrigerant passes through a metering device which regulates the flow to the evaporator coil. In smaller and older systems this device consisted of small copper tubes called capillary tubes which lowered the flow and pressure. Others use specialised flow restrictor devices. Modern high efficiency systems use a device called a thermostatic expansion valve. This device senses the refrigerant temperature at the outlet of the evaporator and automatically adjusts a valve to regulate refrigerant flow.
These devices cause the refrigerant pressure to go down. Air is circulated over and through the evaporator coil by the fan on the furnace/air handler. Heat from the home’s air is transferred to the refrigerant. This heat raises the temperature of the refrigerant above the saturation point and it changes back into a gas. The flow of refrigerant is regulated so that extra heat is added above the saturation temperature. This is called superheat and is added to ensure that the refrigerant stays in the form of a gas as it goes through the compressor. This refrigerant gas is then pumped back to the condenser where the process repeats itself over and over.
When the thermostat senses that the home’s temperature is below the set point, the contacts are opened and control voltage is no longer supplied to the furnace or the air conditioner.
The size of an air conditioner is expressed as tons of cooling capacity. A ton is equal to the ability of the system to remove 12000 btu of heat per hour. Btu stands for British Thermal Unit and is a standard measure of heat.
The relative measurement of a unit’s energy use to perform this cooling is its SEER rating. SEER stands for Seasonal Energy Efficiency Ratio and is a ratio of the cooling output divided by the power input. In general terms, the higher a unit’s SEER number, the less electricity it requires to produce the rated amount of cooling.
Higher efficiency air conditioning units:Higher efficiency units typically have some special features. They usually have two stages (speeds) of operation. In some cases this is accomplished by having two compressors in the unit. One is run on low speed and both are energised for high speed. In other cases, this is achieved by having one compressor with two motors inside. One motor is energised for low speed and the other is energised for high speed operation. On some high efficiency units the condenser fan motor can operate in low or high speed too.
The highest efficiency air conditioner uses an advanced compressor called an inverter drive. This compressor has a motor that runs on direct current (DC) instead of the normal alternating current (AC). This DC power can be easily varied to provide almost an endless number of speeds. This allows the unit to precisely match the cooling requirements of the home and can save a lot of energy.
Air conditioning troubleshootingIf your air conditioning problem is that the unit is not working at all:
If the problem isn't the thermostat or remote, check the breaker.
The possible problems include:
If your breaker trips instantly as soon as you try to turn it on, stop and have a professional technician check your unit. Possible causes of this issue are direct short or ground in the wiring, compressor windings or fan windings, or a direct short or ground in relay, contactor, or transformer windings.
One reason not to keep resetting a breaker that trips instantly is that the shorted or grounded wiring could be sparking when you reset the breaker, and it could be a fire hazard.
Here are some examples of additional air conditioning problems that could be caused by repeated
The problem may be that your air conditioning unit just doesn't seem to be cooling as well as it should.
If the problem persists, see a professional technician.
If your air conditioning problem is a water leak:
If your air conditioning unit is making a strange noise:
Charging refrigerant in winterUsing your air conditioning charging station in the winter months can present its own problems. The refrigeration gas (R134a) does not flow too well if the external temperature drops. Some machines have their own on-board heaters but others rely on recovering some refrigerant from the vehicle or from a supply cylinder. One of the benefits of recovering and recycling refrigerant is the heat generated through the compressor. The charging station works exactly the same way as a vehicle: if you draw gas from a low pressure area and compress it, the low pressure side gets cold and the high pressure side gets hot. This hot high pressure liquid that comes from the recovery side gives us a benefit when charging into the car as the liquid races into the system quicker.
One of the drawbacks with charging liquid refrigerant into an evacuated system is that as soon as the liquid is released it wants to expand into a gas and equalise the pressure between the car and the charging station. If this takes place before the full charge has been delivered then the station effectively undercharges the car and the charge is not complete. A simple trick to rectify this is to close the red HP valve on the station or the HP coupler and start the car. The compressor on the vehicle will then pull the rest of the refrigerant into the vehicle and finish the charge. The gas charge is usually weighed in from a scale platform on a modern machine and the scale doesn't care how the refrigerant is decanted.
The Moisture InsideIf you find that there is a regular problem with charging, check that the vacuum pump is in good condition. The oil level and oil condition is critical. The vacuum pump oil lubricates the pump and provides the seal for the pump blades. If the oil level is too low, the seal breaks down and the high vacuum required cannot be reached. The quality of the oil is also important.
A poor vacuum can cause many problems because it does not dehydrate the system properly. Any moisture in the car’s system can be devastating, as the combination of R134a and moisture creates hydrochloric acid. This quickly saturates the filter dryer making it useless and then starts to destroy the whole system from the inside out.
With the winter months being cold and damp, moisture is very difficult to keep out of an open system, especially if the vehicle has been damaged and stored for a while. Because the system is effectively charged with refrigerant (R134a), as soon as it escapes and evaporates it leaves the inside of the system very dry. Moisture is automatically attracted to the dry areas and considerable amounts of water can form inside the pipes and condenser. This is unavoidable and only an extensive evacuation can rectify it. In this case a new filter dryer must be fitted and the system evacuated immediately. If we break into the system and have to leave it for any length of time then taping the open hose ends up with tape can be a great help. This obviously stops moisture and dust from entering the system and causing unnecessary contamination. A good vacuum gauge can be critical in determining when sufficient vacuum has been achieved to sublimate (remove) moisture.
A very cold car can be difficult to recover the gas from. This can be due to the pressure being very low in the system and warming the car up is a great help. Also, if the recovery cylinder has picked up air (remember air cannot be condensed) the pressure increases and the compressor will struggle. As a tip, it is always worth keeping the new supply cylinder near the station so that they are at the same temperature.
Decrease Your Refrigeration Recovery TimesIn most recovery applications we are all in a hurry to recover the most amount of refrigerant in the quickest time available. This can be made easier by using the ‘Push-Pull’ method. Otherwise you must ensure that your recovery unit does have the refrigerant throttle to it via the manifold to prevent liquid slugging, which will cause damage to the compressor.
In all applications you should wherever possible have your cylinder under vacuum and as cool as possible. This will also help speed up the recovery process.
What is the Push-Pull method?
In simple terms, you draw vapour off the top of your recovery cylinder, run it through your recovery unit and then back into the system you are recovering from. Next, run a hose from the liquid dipper tube on your receiver to the liquid in your bottle.
This method is only useful when more than 7kg of liquid is known to be in the system and it can be easily isolated.
General maintenance for Recovery Machines:The actual requirements on Recovery Machines are minimal but important!