Inevitably, air conditioners seem to fail at the most inconvenient times: when it’s hot and you have to wait for the repairmen. While professional repair is usually necessary and recommended to ensure that your air conditioning unit works efficiently and effectively over the long run, there are some issues that can be quickly and easily fixed, enabling you to bypass the long, hot wait. Here are some of the most common AC problems people experience and some tips for air conditioning troubleshooting. The air conditioner isn’t cooling: If the unit is running but your home isn’t cooling as it normally does, the first thing to do is to lower the thermostat five degrees and give it some time to see if this fixes the problem. Keep in mind that if the temperature outside is particularly high, your air conditioner may not be able to achieve your desired internal temperature regardless, particularly if you have a lot of windows bringing in heat. Inadequate air cooling may also be due to a dirty evaporator or dirty or blocked condenser, which unless you know what you are doing should probably be looked at by a certified technician.

A faulty compressor may also be the cause, which will definitely require professional repair. The AC unit is blowing warm air: The most common reason that an air conditioning system blows warm air is due to dirty filters. Essentially, in this case the system is producing cold air but that air is not able to flow through the ductwork. how long should an ac unit lastSo if this issue occurs, the first thing you should do is check the filters. ac unit in a carOther easy things to check is whether leaves and other debris are not obstructing the airflow. how much power does a ac unit useIf everything looks clear, then you will need to wait for a repairperson, as the problem is most likely due to insufficient refrigerant, which only licensed repair technicians are able to replace.

The unit shuts on and off repeatedly: In most cases, this problem is caused by a dirty or blocked condenser unit, or a dirty evaporator. Most of the time, having the unit thoroughly cleaned, with all obstructions removed, with solve the problem. The air conditioning unit is making strange noises: While some noise coming from the unit while it is running is normal, if you are hearing strong vibration or loud rattling noises then something may be wrong and a professional should probably look at the unit. If you hear a squealing noise, then the unit should be shut off and a professional called at once, as it could be that the belt connecting the blower to the motor has slipped, and you don’t want to end up damaging the motor. Keep in mind that cleaning your air condition, while doable, should only be performed if you have a basic understanding of the parts of the unit. Also, any time the coolant is involved, you will definitely need the help of a professional HVAC contractor.

Regular professional maintenance of the unit will also help prevent issues like the above from occurring to begin with.Written Written Written Why do we need cooling?The body core temperature is around 37°C and that of skin is 33.7°C but the body constantly converts chemical energy to heat. Hence to maintain this temperature we need to dump that heat in surrounding environment. Mechanism of heat rejection :Radiation : Q = constant * {(body temp in K)^4 - (surrounding temp in K)^4}Convection Q = h * Area of body *{(body temp) - (surrounding temp)}Evaporation Q = he * Area of body *{(body vapour pressure) - (surrounding vapour pressure)}   Out of which convection and evaporation play major role as temperature difference between the body and the surrounding is very small to carry out significant radiative heat transfer.  Convective heat transfer on the other hand plays important role. It actually moves heated air from your skin and replaces it with cool surrounding air. In natural convection this happens due to density difference between hot air and cold air.   

Evaporative heat transfer takes place as water from the body evaporates through pores in skin and takes away the heat of evaporation. The driving force for this mechanism is vapour pressure of water in surrounding air. Why air circulation is important?Convective heat transfer coefficient "h" in the equation depends on the velocity of air. Roughly it is related to velocity V as h=8*V^0.6. Evaporative mass transfer coefficient also varies roughly the same. Hence by increasing velocity of air around the body, we can dump more heat. This reduces the temperature difference required for heat transfer. Logically one can increase the set point of AC to higher temperature (27-28°C instead of 24-25°C) and still have same level of comfort. This will help AC to run the compressor for less amount of time.About the heat rejection from fan Fan motors are much more efficient compared to compressor. Efficiency of a typical 50 W fan motor is around 80-85% hence the heat loss is hardly 10 W, which is very small.

(Human body dissipates 50 to 80 W even while sleeping)So practically there will not be load addition due the fan heat loss. But turning on fan will only work on living things only as it does not actually reduce the temperature. So turn it off while leaving that room. To conclude always use fan with AC as long as the room is occupied.Fan motors are the unsung “heart” of HVAC equipment. They work unobtrusively and quietly for years, often under tough conditions. They don’t need a lot of love, but they do need periodic attention and it’s up to you to provide it. The cost of overlooking regular testing and maintenance of motors can be an HVAC system that grinds to a halt, so be sure to check the motor on every maintenance and service call. When you arrive on a jobsite in which a unit’s fan motor is not working or the high-limit switch has tripped, the first thing to check is power to the motor and/or unit. If there is proper voltage, check the low-voltage control circuit. Check for proper voltage at the transformer and check for a fuse in the low-voltage circuit.

Make sure the circuit breaker is not tripped (or the fuse is not blown). If the circuit breaker is tripped (or fuse is blown) or if the transformer is bad, it could indicate a short in the motor. In that case, check the windings in the motor before turning the power back on. To check the windings of a motor for an open or a short, you’ll need to measure the ohms. If the unit has a 120V motor, it will most likely have three or four colored wires (black, red, yellow, and blue are common), a white wire, and two brown wires. Do a resistance check between the white wire and each of the colored wires. The higher the resistance, the lower the speed, with each color representing a different speed: i.e., four colored wires, 4-speed; three colored wires, 3-speed. You want to see a resistance reading. If you get a zero reading that means the motor winding is shorted and may be the cause of the tripped breaker/blown fuse. If you get an infinite reading (overlimit or OL on most digital meters), that indicates an open motor winding.

If either of these conditions exist you will have to replace the motor. When checking the ohms on motor windings, many technicians have difficulty determining an open winding vs. a shorted winding. But it’s really not hard to tell the difference between the two. It should show a resistance. If it shows a zero reading it probably means the windings are shorted out. If it shows an infinite reading, that means the windings are likely broken or open. A good trick to remember this is that an infinite reading means the greatest resistance in the world. It’s like an open door leading to infinity — in other words, an open winding. Meanwhile, a zero reading means the load is taking a short cut around it — in other words, a short. That’s just a simple trick to help you remember that a zero reading means a short, and an infinite reading means an open or broken winding. Just because a motor is not running doesn’t mean the motor is bad. If the power is correct and the motor is neither shorted nor open, check the capacitor (that’s where the two brown wires go).

A capacitor helps the motor run and gives it more torque. If a motor doesn’t have the torque to turn the blower wheel or the fan belt, it won’t start. So the capacitor plays a big role. The capacitors on most of residential blower motors are very small, so technicians tend to overlook them. You should discharge the capacitor before handling it. Using a capacitor tester, make sure the microfarad reading is within 10% of the rated capacitance on the capacitor. It will be a number listed in uF or mfd, depending on the manufacturer. If the reading does not match the rating, replace the capacitor. Checking 240V motors is slightly different because you will have two hot wires and most will be only single-speed. But you still ohm-out the windings to check for open and shorted windings and check the capacitor the same way. Finally, when doing a routine maintenance call on a unit, always check and clean the motor. One of the biggest problems with motor burnouts is dirt. The main thing to tell homeowners is to keep everything clean.