Advances in Technology
So much has changed in the world of air conditioning in recent years that if your system has almost any significant breakdown (or if it’s just not keeping you as cool as it used to) it may be worth replacing it instead of repairing it. A lot of people might be asking "Can a dirty air filter cause the air conditioner not to cool?" A dirty air filter restricts the flow of cold air, causing it to build up inside the air conditioner and lower the internal temperature
As of 2010, for example, manufacturers must use a new kind of refrigerant that’s not an ozone-depleting chlorofluorocarbon. And a new system can use less than half the electricity of your old one while doing a far better job of keeping you cool and comfortable. Chances are that if you are using R-22 in your HVAC unit that you must replace your unit within the next two years.
If your air conditioner is more than eight years old, repair is probably not worth the expense, unless it’s a simple problem like debris clogging the condenser unit or a worn fan belt. Still, to best weigh your repair-or-replace decision, ask your contractor to assess not just the condition of your existing equipment, but also the ducts that deliver the cool air and the overall quality of the insulation in your house. Improving those elements might increase the effectiveness of the system as much or more than installing new machinery.
Inspect the Condition of the Ductwork
You could upgrade to the highest efficiency gear available and still not feel comfortably cool on hot days. That’s because the mechanicals are only part of the central air system. The average house’s ductwork leaks 10% to 30% of its air before it can reach your living space, according to Pacific Gas & Electric. Before deciding whether to repair or replace your condenser and blower units, your technician should run a duct-leakage test, by sealing the vents and measuring how much air escapes the system.
If the ducts are inefficient, he can locate and seal the gaps, typically for $25 to $35 per vent (per “run” in industry jargon), or replace the ductwork entirely with new, insulated pipe for around $100 per run, according to Guiles. Your technician may recommend doing the duct improvements in conjunction with replacement of the mechanicals or may recommend only one or the other job.
Consider the Building Envelope Itself
If your house is poorly insulated, it’s putting a strain on your aging air conditioner. Resolving the house’s flaws may mean that your old system will have enough cooling power to continue to do the job for a few more years. Or it may enable you to buy a smaller replacement system, lowering your upfront and ongoing energy costs significantly.
Your heating and cooling contractor should assess and, if necessary, upgrade the building envelope. For example, he might seal gaps and cracks in the outer walls and attic floor, or he might blow insulation into the walls, either of which could knock as much as 30% off your heating and cooling costs. Insulation also may get you a $500 federal tax credit, and in some cases, it may be a more effective solution to your cooling problems than replacing your equipment.
Make Sure a New System Is Sized Right
If you decide to replace, make sure the contractor’s bid includes a load calculation, which is a computer printout showing how big a system you need and why. Air conditioning is measured by the ton, which is the cooling power of a one-ton block of ice melting in 24 hours. Some old-school installers use a ballpark estimate for sizing equipment—say, one ton for every 400 or 600 square feet of living space. But that typically leads to systems that are too big, according to Greg Gill of Action Air Conditioning and Heating in San Marcos, Calif. Not only do over-sized systems cost more, but they also do their cooling work too quickly, which means more frequent on/off cycles, wearing out components and gobbling electricity. Plus, they don’t have a chance to effectively dehumidify the air.