Are You Getting What You Paid For?
When you shop for a furnace or air conditioning unit, there’s a real good chance you’ll get confused. You’ll hear different names, numbers, abbreviations and acronyms used to describe the capacity and efficiency of the equipment. The Federal Energy Standards Act was enacted to help clear up some of this confusion and to give a home-owner some basis of comparison between different heating and cooling units. Two terms you will hear quite a lot if you do much shopping are the SEER and AFUE rating. The SEER (Seasonal Energy Efficiency Ratio) describes how much heat in BTU’s (British Thermal Units) a particular unit will remove for each watt of electricity it consumes. Since you pay for your power bill on the watts you use, the higher the SEER, the less your electric bill is supposed to be.
Sealed Ducts Mean Lower Utility Bills
An AFUE (Annual Fuel Utilization Efficiency) is an average of how much heat a furnace delivers for each $1.00 you pay for fuel. So, again, the higher the AFUE, the lower the heating bill is supposed to be. But, does it really happen that way? Yes and no. There is a lot more to an efficient heating and cooling system than ratings. Equipment ratings are calculated in a laboratory setting. It includes no duct work, no consideration for installation, and no house. Obviously, this is not the real world. In reality, your chances of buying a 11 SEER unit and getting 11 SEER in your home may be less than 2 in 10. The biggest factor that will determine how close to the ratings the unit will perform is the design and installation. Some of the variables are; oversizing, poor duct design, improper refrigerant charge and improper control wiring.
What are the chances of a homeowner getting a system installed correctly? In 1990, a comprehensive field study was conducted to see how many systems had these problems. A large number of homes were selected and each location was visited by a team of specialists. After field investigation, it was found that every home in the study had major problems with the equipment, ducts system, or in the building shell itself. Two thirds of the homes had been serviced in the previous two years and the heating contractor did not identify any problems. Of the homes studied, 56% had improper refrigerant charge. Over 66% of the units had insufficient airflow inside the home. Improper refrigerant charge was estimated to waste about 12% in energy and compromise the equipment life. A deficiency of only 20% in indoor air flow on a heat pump or air conditioner degrades the SEER rating by 17%. This means a 10 SEER unit will operate as an 8.3 SEER unit. Duct leakage greater than 150 cubic feet per minute was found in 93% of the homes tested. Control problems were found in 63% of heat systems. House shell problems occurred in every home studied.
An average of 24% energy savings was accomplished by a program that diagnosed and repaired these problems. This study demonstrated that most heating and air conditioning contractors are not able to identify and solve the problems that lead to high energy bills and discomfort. This may be attributed to a business environment that concentrates on low first cost and lowest bid with no regard for future operating cost.
“The contractor business is built on a low bid, least cost system that precludes you from spending the time to find out what’s really wrong with a unit. It’s economically impossible to do the job right. The field technicians may have been trained to do the job properly in a good school, but the workplace pressure is to do it fast and dirty. It’s a major economic mistake for a customer to make the hiring decision based on cost instead of quality. But, of course, everyone does just that all the time, and you see bad work.”
John Proctor, PE
Proctor Engineering Group