A 3-ton air conditioner removes about 36,000 Btu per hour at rating conditions. Airflow rules key off it: nominal 400 cfm per ton for standard comfort cooling, lower in humid climates for better dehumidification and higher in dry ones. Chillers are rated in tons too, with efficiency in kilowatts per ton.
Ton and a half for the bonus room is plenty, that's 18,000 Btu, and set the blower around 525 cfm.
Nameplate model numbers usually hide the size: a 36 in the model number means 36,000 Btu, or 3 tons.
Also heard as
- TR
- RT
- ton of refrigeration
Related terms
CFM
Cubic feet per minute: the standard unit of airflow through equipment, ducts and outlets.
Cooling load
How much heat and moisture a cooling system has to pull out of a space each hour to keep it at design conditions.
Chiller
A refrigeration machine that cools water or glycol, which is then pumped to coils to cool a building or process.
EER
Energy efficiency ratio: cooling output in Btu per hour divided by watts of input at one hot, full-load test point.