Changing Filters: How & Why

Trust This Old House to inform us on how and why you need to change your air conditioner's filters monthly:

Dirty filters kill your AC's efficiency, so install a new one every month during the cooling season for central and window units (or clean them if you've got the washable type). Look for the filter's minimum efficiency reporting value, or MERV, which ranges from 1 to 12 for home AC units; the higher the number, the better filtration it provides (and the more energy needed to pull air through it, so balance air-quality concerns with energy costs).

How Air Conditioners Work

Today, a little educational message about how air conditioners work from How Stuff Works.

The actual process air conditioners use to reduce the ambient air temperature in a room is based on a very simple scientific principle. The rest is achieved with the application of a few clever mechanical techniques. Actually, an air conditioner is very similar to another appliance in your home -- the refrigerator. Air conditioners don't have the exterior housing a refrigerator relies on to insulate its cold box. Instead, the walls in your home keep cold air in and hot air out.

Air conditioners use refrigeration to chill indoor air, taking advantage of a remarkable physical law: When a liquid converts to a gas (in a process called phase conversion), it absorbs heat. Air conditioners exploit this feature of phase conversion by forcing special chemical compounds to evaporate and condense over and over again in a closed system of coils.

The compounds involved are refrigerants that have properties enabling them to change at relatively low temperatures. Air conditioners also contain fans that move warm interior air over these cold, refrigerant-filled coils. In fact, central air conditioners have a whole system of ducts designed to funnel air to and from these serpentine, air-chilling coils.

When hot air flows over the cold, low-pressure evaporator coils, the refrigerant inside absorbs heat as it changes from a liquid to a gaseous state. To keep cooling efficiently, the air conditioner has to convert the refrigerant gas back to a liquid again. To do that, a compressor puts the gas under high pressure, a process that creates unwanted heat. All the extra heat created by compressing the gas is then evacuated to the outdoors with the help of a second set of coils called condenser coils, and a second fan. As the gas cools, it changes back to a liquid, and the process starts all over again. Think of it as an endless, elegant cycle: liquid refrigerant, phase conversion to a gas/ heat absorption, compression and phase transition back to a liquid again.

It's easy to see that there are two distinct things going on in an air conditioner. Refrigerant is chilling the indoor air, and the resulting gas is being continually compressed and cooled for conversion back to a liquid again. On the next page, we'll look at how the different parts of an air conditioner work to make all that possible.

How Many Tons Do I Need?

Whether you want to install a window unit to cool a single room or are putting in a central air conditioning unit to cool the whole house, it is good to remember that bigger is not necessarily better. A unit that is bigger than is required will not only have a higher initial cost, it could cost you more by short cycling. Of course a unit that is too small can quickly run up your energy bill by running constantly in a futile attempt to keep the area comfortable

Manual J
The Air Conditioning Contractors of America is the industry organization responsible for developing a method for calculating residential cooling loads. The result is the Manual J. Professional contractors should use it to determine the proper size of any home air conditioner they plan to install. Manual J takes into account numerous factors including the average geographical temperature, type and amount of insulation, ceiling height, exterior construction materials and square footage.

Homeowner Calculations
Most do-it-yourselfers don't have access to Manual J, nor to the sophisticated tools available to professional installers. Still, armed with a tape measure and hand-held calculator, most people can make a relatively accurate estimate of their cooling needs. The process is simple--measure the length and width of the room to be cooled and multiple the two factors to get the square footage of the room. Repeat the process for each additional room that is to be cooled and add all of the sums together to get the total square footage that requires cooling.

BTU to Ton
A ton of cooling capacity is equivalent to the cooling effect of a ton of ice melting over a 24-hour period. However, most air conditioning units today are measured in British thermal units, so a little conversion math will be required. Twelve thousand BTUs is roughly equivalent to 1 ton of cooling capacity. A well-insulated room with 100 square feet will require a 4,000 to 6,000 (a half ton) BTU air conditioner while a 12,000 BTU (one ton) unit can cool up to 500 square feet. A 2-ton (24,000 BTU) central air conditioning unit can effectively cool a 1500 square-foot residence.

Source: eHow

NATE Certified

Each of our technicians is NATE certified. NATE is North American Technician Excellence, the leading non-profit certification program for technicians in the heating, ventilation, air-conditioning and refrigeration (HVAC/R) industry and the only test supported by the entire industry. NATE aims to help regulate our industry – and make quality the norm, not the exception with their 5-year renewable certification.

Nationwide, there is a shortage of HVAC/R technicians. Worse, there is a more severe shortage of verifiably trained HVAC/R technicians. Having a certified technician is important because:

• A recent American Home Comfort Study reports that 88% of homeowners believe having a certified technician repair or install their home comfort system is important to them.
• Utilities note that poorly installed and badly serviced units waste energy and cause consumer electric bills to soar.
• Half of consumers defer retro-fits or new installations because they don’t know which contractors have competent technicians. In other words, they are living in less than “comfortable” situations because they don’t know which contractors they can trust to do the job properly.
• Manufacturers note that a third of units returned as “defective” are actually “installer error.”

Certification is not just about contractor professionalism; it’s about customer assurance. Contractors whose technicians are NATE-certified can legitimately claim that their technicians have passed a stringent certification test national in scope, ultimately leading to increased customer service and business profitability.

Source: NATEX

Bad News for Old ACs

Older model air conditioning units use R-22 coolant. These units are being phased out in favor of R-410A coolant, which is more environmentally friendly. This means that the old coolant will now cost about triple what it used to, if you can find it at all.

If you have recently replaced your air conditioner, you are in good shape! If not, the cost of buying the old coolant, and difficulty obtaining it over time, are going to add up. Also, forget trying to sell your place with the old unit. The buyers may have you put in a new unit before the sale.

Source: Fox News

EPA Tips

The EPA weighs in on some ways you can incorporate their tips into your air conditioning for the good of your home, your wallet, and the planet.
1. Look for ENERGY STAR qualified products
   When buying new products, such as appliances for your home, get the features and performance you want AND help reduce greenhouse gas emissions and air pollution. Look for ENERGY STAR qualified products in more than 50 product categories, including lighting, home electronics,heating and cooling equipment and appliances.


2. Heat and cool smartly
   Simple steps like cleaning air filters regularly and having your heating and cooling equipment tuned annually by a licensed contractor can save energy and increase comfort at home, and at the same time reduce greenhouse gas emissions. When it's time to replace your old equipment, choose a high efficiency model, and make sure it is properly sized and installed.


3. Seal and insulate your home
   Sealing air leaks and adding more insulation to your home is a great do-it-yourself project. The biggest leaks are usually found in the attic and basement. If you are planning to replace windows, choose ENERGY STAR qualified windows for better performance. Forced air ducts that run through unconditioned spaces are often big energy wasters. Seal and insulate any ducts in attics and crawlspaces to improve the efficiency of your home. Not sure where to begin? A home energy auditor can also help you find air leaks, areas with poor insulation, and evaluate the over-all energy efficiency of your home. By taking these steps, you can eliminate drafts, keep your home more comfortable year round, save energy that would otherwise be wasted, and reduce greenhouse gas emissions.

Ethical Repair Work

Using an ethical contractor like GMC protects you from unnecessary repairs. If you do have to call for service, some unethical businesses will charge you for items not needed, as in this investigation:

CBS Atlanta Investigates contacted four companies for a general check-up on a heater that worked perfectly. One company did great, but the others recommended repairs ranging from a few hundred dollars to over a thousand dollars for what our experts said were completely unnecessary repairs.

CBS Atlanta News installed hidden cameras in a home where the heater was located to document each sales pitch. Then we had our heater inspected by an expert, Staton Conditioned Air, who has a complaint-free history with the Better Business Bureau.

"Nothing obvious needs to be replaced," said the expert from Staton Conditioned Air, giving the heater a clean bill of health.

"The power will come to it, to come on, it will not come on, but the gas will still seep out," a Bardi technician told Saltzman during the hidden camera investigation...Whenever it gets like that, the gas will keep coming. And if the gas builds up, you know what's going to happen. So we don't want that," the Bardi technician said. Bardi Heating and Air upsold the heater repair costs by $264 for a hot surface igniter, which experts from Staton Conditioned Air said weren't needed.
The next call was to Chuck Maddox at Maddox Comfort Systems. Maddox misdiagnosed the dual-fuel heater and said it wasn't working properly. He recommended replacing the control board and a new thermostat. "I'm gonna say $300 for the thermostat," Maddox said. The control board cost an additional $350.
The most expensive upsell was made by Mechanics Heating and Air Conditioning in Marietta..."When these start to go bad they just explode and stop working," the Mechanics technician said about the heater's air conditioner capacitor. "I recommend the booster, it is extra protection," he said. The technician also suggested a refrigerant top-off, to fix what he claimed was a leak.Mechanics also recommended cleaning the heater's air conditioning coils and cleaning the flame sensor. The flame sensor cleaning is a service that takes about two minutes, which another company did for free, but Mechanics charged $79 for it. Mechanics' biggest sales pitch was a duct cleaning for $875, padding the bill for more than $1,400.

Source: CBS