I have not done any maintenance on my central air conditioning system since I bought my house five years ago. Everything seems to be running fine but is there some sort of maintenance I should be doing regularly?
Every year or two I call out a professional company to check the coolant levels and check for any mechanical defects since I don't have all the gear to do it myself.
Aside from that I just try and keep the area free of debris and anything that could damage the unit. In my case I have a tree off to the side and several branches hang over the unit which I trim back, don't want a branch falling off and spearing through the unit.
Most local HVAC service companies offer an annual service plan where they come out once a year (twice a year for a heat pump), check over everything in the system (indoor and outdoor), clean off the coils, replace the air filters, etc. They will measure the voltage and resistance of various electrical components in the system, as well as measure the temperature of the coils to see if anything is out of whack.
If you have a service contract, there really isn't anything else you need to do for maintenance except make sure the outdoor unit isn't overgrown with grass/leaves/whatever.
Around here, a service contract for a heat pump (2 visits per year) runs $150-$200 per year. I think it's in the sub-$100 range for just an A/C unit, since they don't have to care about both heating and cooling.
I also have a humidifier plumbed into the HVAC system with a moisture pad that has to be replaced annually. Replacing the moisture pad is covered as part of the my service contract (as well as the air filter).
Most of the HVAC companies around here will also give you a small discount on repairs if you have a contract with them (call you a "Preferred Customer").
Check/Clean/ Change filters or Electronic air cleaner, inspect blower motor wheel for cleanliness and alignment, check capacitors capacitance, check evap coil cleanliness and ability to transfer heat(delta tees), check filter driers inlet outlet temps, anything above 3 degrees is a restriction/moisture, condenser coil cleanliness and ability to transfer heat. 10 degree delta tees are acceptable. Inspect dual capacitor and contactor voltage drop across contacts. Voltages exceeding 1 volt mean the contactor should be replaced(according to mfgs recommendations). Generally not performing annual maintenance will also void manufacturers warranties or labor warranties. Two schools of thought on checking refrigerant levels are it should be checked annually to see if there is a leak that's formed or you shouldn't because every time you gauge up you're removing charge from system. With new low loss hoses and ball valve hoses refrigerant loss is kept to a minimum so it's less of a concern. Then again if you just put a system in a year ago and you're just doing basic check-up, getting involved isn't necessary. A good tech will be able to know when he/she should be gauging up based on the temperature readings they get while checking the indoor unit, after letting the system run for 15 min, which is usually done while performing the AHU maintenance.
As far as I know coolant levels are checked if you have a great deterioration in performance.
The manual that your device has gives you details on what you should clean each year.
My split type A/C have LEDs that inform you as well, when regular maintenance should be contacted ( which is described in the manual).
Yes, you should be doing maintenance on your AC unit, but not just once-a-year maintenance.
Keep the air filters clean, and if you have been lax in keeping the air filters clean, considering opening the upper air handling unit and cleaning the inside coils. There are spray on solvents that will break up the gummed up dust and dirt. Use common sense, turn off the outside circuit breaker first. Also turn off the circuit breaker on the inside air handling unit.
While you are up there, take up a bucket of water. Make sure that your pan doesn't leak or drip by carefully pouring the water into it. There is an internal pan, so the external pan is not tested very often; however, there are many cases where the external pan has failed in some manner, which you only discover after the internal pan's drain line gets clogged.
For the outside unit, you will want to occasionally clean the coils. Find the disconnect and pull it. It will keep the outside unit from turning on while working on it. It is a secondary safety measure as you've already turned off your house's AC circuit breaker. Then you can use a garden hose to spray water through the fins from the inside out. If you cannot manage to get a clear stream of water, you might have to also remove the fan / wire mesh shield.
I typically don't bother having my coolant checked. It doesn't disappear or wear out, it leaks. If it is leaking, you will know soon enough by the inside coil freezing up. There are other reasons the inside coil can freeze up, but if you have sufficient air flow (open vents and unclogged filters) and verify that there's not an electrical problem causing your compressor to turn on without turning on the internal fan, then you can deduce you have a low coolant problem. In that case, you need to get a proper repairman and not let him top off the coolant until he locates the leak and fixes it. It's tempting to let him do otherwise, but you'll just be paying for it again, sooner than you think.
The most important thing is air flow, both indoors and outdoors. The air filter needs to be clean and not too high of an efficiency in the AC mode as the high efficiency filters reduce air flow by about 1 ton of refrigeration I have learned by using Honeywell's Enalysis system on hundreds of homes. Heat season is better able to endure a high efficiency air filter. Keep debris off and away from the ac unit, chemically clean with coil cleaner available at HVAC parts houses and appliance parts stores, it will strip the coils and re new performance. refrigerant theoretically should never need to be added , if so you have a leak. replace time delay fuses inside the electric disconnect at the unit every 2 yrs.