Hello.
There is a BIG myth in the air conditioning world that the air sales people don’t really care if you understand. In fact, it seems that they would probably prefer you didn’t. And it’s costing consumers more than just a bundle of money up front.
Too SEER or not too SEER – That is the question
Air conditioning systems for homes work on the principle of compression and decompression of gas. The gas is run thru a compressor outside the house because this step creates heat. It is then channels inside to the air conditioning unit where it is decompressed (cooling) in copper coils and air is drawn across them to cool the air. I’m trying to keep this as simple as possible. Moisture is accumulated on the coils in the process, drips into a pan and is run outside the house.
The more copper coils, the cooler the conditioner can make the air and, the more expensive the unit costs. But, more copper doesn’t equate to more moisture being drawn out of the air and I’ll explain in a second. The ideal configuration is to have the unit matched well with the space being cool. Not too many copper coils and not too few.
The trick, particularly in a humid climate, is to have the unit running a sufficient amount of time to draw air across the coils and pull moisture out. Thus cooling and dehumidifying the air.
Enter the SEER number or Seasonal Energy Efficiency Rating. The higher the SEER, the faster the unit cools. And you hear numbers like 14 SEER, 16 SEER, 18 SEER and so on. So, the higher the SEER you can afford the better and cheeper your home will be cooled, right? No. Not at all.
Because, if the unit has too hight a SEER rating for a house, it will cool it off too fast and not take enough moisture out of the air to make the house comfortable. Since the process is a dehumidifying process, moisture is removed from the house as the unit runs. If it cools too fast and shuts off quickly, much less humidity is removed than is desirable.
The idea combination is to have the unit with a SEER rating that matches the needs of the house (square footage) and duct work that distributes the air. The unit should run just long enough to pull a sufficient amount of humidity out of the air making the perfect mixture of coolness and moisture.
The misunderstanding comes when the home owners hear that a higher SEER rating cools the house more efficiently and are not informed that this could cause a lack of sufficient dehumidifying to make the house comfortable. The higher the SEER rating may make the house more energy efficient but less comfortable.
The bottom line is, if the original unit was well matched for the house and creating a comfortable living space when it was working properly, then stay with that SEER rating. Or have the whole system, including the duct work, evaluated to determine the best unit and proper SEER rating for the house.