Economizers = Free Cooling
It’s no secret that running air conditioning equipment costs money. In fact, if you operate a typical commercial office building in Southern California, air conditioning comprises 30-40% of your monthly energy bill. The primary energy users in packaged air conditioning equipment are the compressor(s) and supply fan(s). The good news is that about 35% of the year, your building can be cooled without turning the compressor on (or without running all of the compressors). On a smaller rooftop packaged unit, that equates to about 60% less operating energy cost because the compressor isn’t running.
How is this accomplished? The answer is, with an Economizer. An Economizer is comprised of a motorized damper, a few sensors, and a controller. It works by measuring outside air temperature and deciding when it is economical to circulate 100% outside air to satisfy the space cooling set point rather than run the compressor. When there is a call for cooling and it makes sense to use outside air, the economizer controller will command the damper to open to let in outside air. This is a crude explanation of the sequence of operation, but the idea is that they are simple in both construction and operation. In spite of this fact, the overwhelming majority of existing economizers are in disrepair or are disconnected, and in most cases the building owner/operator is not aware of this. If you have an economizer installed, then test it to make sure it works and if it doesn’t then FIX IT. There are off-the-shelf economizer kits available for most makes and sizes of small packaged AC equipment. You’ll find that the energy savings will pay for a new installation in 2-3 years. If a repair is all that is required, the simple payback will be much less. Economizer products that have recently become available are more intelligent and intricate than past controls which means they can capitalize on even more available “free cooling” throughout the year (They also are designed to meet the new Title 24 code for package AC equipment).
There are some strategies that must be decided on for new economizer installations, but the important message is: You are losing money if you aren’t investing in a new economizer or repairing your existing one. Also so you are aware, current California Title 24 energy code requires economizers on new or replacement packaged equipment with 6 tons of cooling capacity or greater.