Friday, September 18, 2015

What Kind of Air Conditioner Should I Install?

What brand should I install?  Should I pay extra for the 20 SEER system?  These are common questions.  They're the questions I asked myself when I was doing my remodel.


There are several premium HVAC brands that make good equipment, and there are several second tier brands that also make good equipment.  The truth is, you're probably not going to go wrong on equipment brand.

The top tier brands mostly control their image by controlling who can install their equipment.  Because they set the bar on the installer, they are able to reduce the number of bad installs of their equipment, which are the most likely cause of poor reliability and failures.  The second tier brands tend to be available to anyone, which means that they tend to be installed by more fly-by-night operators, but the equipment itself isn't really that much different.

Once upon a time, brand probably mattered a lot.  The different manufacturers all had their own technologies that they had developed with regard to compressors and heat exchangers and expansion valves and controls.  Some companies were undoubtedly better than others.  That's just no really the case anymore.  This equipment all largely utilizes components from outside suppliers.  Often these are companies that used to be part of the AC manufacturer before those markets became more competitive, but they were spun off and sold decades ago.  Today you'll find that they're all buying components from a lot of the same people.

I like to tell a story about when I was at Enviro Systems and we were developing the 787 galley chillers with Hamilton Sundstrand.  HS is part of United Technologies, the same company that owns Carrier.  They offered to let us use a Carrier test facility in Syracuse to test a new heat exchanger technology, but first they had to, well, have someone go to the facility and see if everything still worked, because nobody had used it recently.  Carrier no longer really needed to test heat exchangers because they just aren't really in that business anymore.  Heat exchangers come from outside suppliers.  Compressors come from outside suppliers.  None of those suppliers are exclusive to Carrier.

Features and Efficiency

The top brands, at the top end of their product lines, for customers willing to pay for premium products, may sometimes offer technologies that are nice, but the truth is that if you're buying anywhere outside of the very top, good features are available even in the budget brands.

So what features do you want?  You want a 2 stage compressor, a variable speed fan furnace, and a thermostatic expansion valve.  You want these because they provide a big improvement in comfort over more basic single stage systems.

When it comes to efficiency, the Seasonal Energy Efficiency Rating (SEER) generally is referenced.  I will save you a lot of boring discussion and we'll just say it's a pretty decent system, but it's not perfect.

  1. Manufacturers tend to advertise based on the maximum SEER rating they can achieve with a particular compressor/condenser pallet.  Note that they will say something like "up to 18 SEER" in the sales literature.  You may not even actually be able to buy the set of equipment they used to get that 18 SEER test rating. At best your system is likely to be a little less efficient than advertised.
  2. Where you live matters.  "Seasonal" calculations are applied, so SEER is more accurate in some locations than others.

Before 2006, a budget AC system didn't have to be very efficient, and SEER ratings ran in the single digits.  In 2006 a minimum SEER rating of 13 SEER was introduced.  In 2015 the minimum was increased to 14 SEER.

Your 2 stage, variable speed furnace will put you in the "up to" 16-18 SEER range.  Anything above 18 SEER probably is going to come at a premium that you probably can't or won't justify.  Doing the math, an 18 SEER system will notionally use 11.1% less power per year than 16 SEER.  20 SEER will provide a 20% savings over a 16 SEER. 22 SEER would only be 27% more efficient than 16 SEER.

As you can see, the returns start to diminish as you continue to increase the rating, and acquisition costs tend to escalate much more quickly than the savings.  18 SEER is really the sweet spot in the market right now.