The right size for an air conditioner is the size that will cool your home on a hot summer afternoon with only about 10 to 15% Btu/hr to spare. When we install more air conditioning Btu/hr than this, it will, especially under part-load conditions, do what we call "short cycling."
Originally posted by jcswaim
How can you tell or test a system to see if it short cycles?
It only runs for a few minutes--maybe five or ten at a time--and then shuts down for a few minutes, before starting up again. In these short cycles it cools the house, but it does a very poor job of removing humidity. it also takes around five minutes on each start-up to get to full capacity cooling! This will greatly lower the operating SEER rating of your equipment, therefore the recommendation of the wide temp differential room TH.
Most room TH's used to have a cooling anticipator that actually caused the unit to keep the room temperature within a very tight differential, --leading to a worst possible short-cycle scenario!
Therefore, decide what you want, a close temp differential or a wider differential with a longer run-time and less on/off cycling for more efficient operating performance! Darrell