| Darrell: Here is Bob Brown's post on SEER from last year" SEER ratings
posted by: bob_brown on 07.01.2006 at 01:53 pm in Heating & Air Conditioning Forum What is SEER, and what does it mean to the homeowner?
SEER is a rating that can be mathematically adjusted to fit a manufacturers design. The conditions that are used are an impossible to achieve criteria. It uses some conditions from a hot climate but generally ignores the difference in temperature from 82F degrees and above. The majority of manufacturers use a formula that uses the best of all conditions to obtain a skewed SEER. This is a variable speed motor fixed to operate in the slowest setting, with a temperature setting at a minimum of 80 F degrees. The humidity is dry or nonexistent. Under these conditions the rating is made. For a hot climate, the SEER is imaginary at best from most manufacturers. The estimated savings does not exist in many designs, because of the artificial test requirements. When coupled with architectural designs that has poor airflow design, and poor designed duct systems, the SEER does not play a significant part in the attempt to save energy. A lesser SEER with proper duct design and without excessive static pressure can perform at 2-3 times the savings, of a higher SEER in a high static design duct. This does not mean rigid duct against flex duct, but in the design of the duct. I believe the usage of oversized filter systems erase any savings derived from a properly designed duct system. If the filter increases the static pressure, the SEER is reduced. One issue that is ignored by most manufacturers, is the ambient temperature and the role it plays in SEER. In a hot climate, a typical high SEER system is degraded to a very low actual SEER, when the temperature is in the mid to high 90’s. In practice, it is my opinion that the SEER drops from 14 to about 1-2 in hot climates I have an ongoing experiment for 10+ years, which reduces energy requirements in a 3-ton residential condenser. The original rating was 9.2 SEER. The unit has maintained an amp draw of 11-12 amps during hot conditions for the last 10 years. The unit was installed as a mixed system 1984. The evaporator coil is about 6000 Btu bigger than the condenser coil. This was the recommendation at the time. Nameplate is 17 amps. I added a waterspray that misted the coil continuously during the summer months. The ambient summer temp is over 90 degrees for the majority of the summer. At 10:00 am the temp is over 90, by 4pm the temp is maximum and usually around 98+ degrees. At 10:00 p.m. the temp is still over 90 degrees. Many nights the temp does not drop below 90 degrees until 3-4:00 a.m.. A 14 SEER nameplate is about 15.5 amps. This is rated at an 82 degree ambient. At 98 degree ambient, the amps are 2-5 amps higher than nameplate when the system is attempting to cool the house. This increase of amps strains the condenser, and shortens its life. The SEER drops to less than half of the rating in the 98-degree weather. I estimate the SEER on many units is probably about 1-2, after the system is beat all month in extreme conditions. When the unit runs continuously, this is not the intentions of ASHREE design recommendations. In fact, they suggest the proper design only run continuously 20% of the time. This is not what current design is today in Texas. In order to satisfy the design requirement of 750 sqft per ton, the system will operate 24 hours a day, 7 days a week, for 3-4 months, then run about 75% of the time for 4 months, and finally it will operate 30% of the time during the remaining warm months of the year. Using current standards of design, the electric usage is triple what it should be. While a lot of claims of designers to control humidity are heard, the price to eliminate 40% humidity is cost prohibitive in N. Texas. Usage of modulating speed motors, increase the SEER rating, but the heat load requirements require full speed with the motors in N. Texas. When the motor speed is at the highest speed, the energy usage is more than a fixed speed motor. The only time the speed can be reduced is when the system cycles. If the system is operating 24-7, then the variable speed is useless, and cost more to operate. Proper design of a system is needed to achieve a higher SEER rating. Improper design affects a higher SEER quicker than a moderate SEER. When a consumer adds an overly thick filter, the airflow is slower, and the SEER drops. When a filter is dirty, the SEER drops. In short, anything that opposes airflow thru the evap coil affects SEER. A hot UV lamp affects SEER. A slower speed blower affects SEER on a hot day. If a system has a TXV valve, the system compensates for the under or over charge condition. On a hot day, the system is always undercharged. This can be explained by the system running continuously to provide enough liquid to fill the evaporator coil. Most college graduates have heard of the ideal gas law pv=nrt. This law is a basic natural law that works. I made average grades in basic chemistry 101, and physics 101. I remember this law 30 years later. I understood it in math problems, but never really understood what it meant until I had evaluated my 10-year experiment, half way thru the experiment. When the pressure goes up, the temperature goes up. When the temperature goes up the pressure goes up. If a motor draws 15 amps when it is cool, and it draws 17 amps when it is hot, the amps are also higher with heat. Reduce the temperature and the amps drop. I repeat, reduce the pressure, temperature and the amps also reduce. Another side effect is when the pressure and temperature drops, the system does more cooling. Yes the cooling increases, so the system does not run as long when the temperature remains high. This is a simple concept, but few owners understand it. Few HVAC technicians understand it. The DOE does not seem to understand it with the SEER ratings. I worried that I was stupid, and could not believe that I was the only one that understood this law. When I discussed my findings with a major manufacturing R&D supervisor, he said Industry doesn’t do it, so we don’t do it. He had a Ph.D., and did not understand the law. For a long time, I thought I was missing something. I was not interpreting the data properly. I was dumb. I finally figured out that I was not dumb. Reduce the temperature and the system works as expected. Reduce the head pressure, and the system works as expected. When the system works properly, the system is not strained, and does not fail as often. The system lasts longer. It costs less to operate. I learned something else, Geothermal works kinda in my area N. Texas, but works better in Oklahoma, and even better in Wyoming. Geothermal is very expensive. Geothermal still uses Freon and compressors. My water spray works almost as good as geothermal. My water spray paid for itself in the first summer of usage, by reduced energy costs. It saved even more money in fewer repairs. The system was never stressed, so it lasted much longer than expected. My system works more efficient than a 20 SEER system. Most systems are only 10 SEER. The new requirement is 13 SEER. My system has worked properly for 10+ years at a very high efficiency. Golly Gee Willikers. | 
