There are four key criteria for choosing the right unit:
Most manufacturers offer 4 different approximate BTU sizes- 7000, 9000, 12000, 15000. You need to know the BTU rating of the PTAC you are replacing. If you are satisfied with its cooling and heating power, do not change BTU sizes. For more on BTU sizing click here.
Most manufacturers off 2 different Voltages- 230/280V and 265V units. These are linking into receptacles that are 250Vor 277V. You need to know the Voltage rating of the outlet of the PTAC you are replacing.
Almost all ALF properties built since the 1970’s have the same standard size shroud or wall sleeve (42″ wide, 16″ high, and 13 3/4″ deep). If you have this size, you can usually pick from any of today’s modern brands. If not, you will need to install a new wall sleeve and grill.
The more BTU’s, the more heating and cooling power a PTAC unit will have. Here is an APPROXIMATE sizing guide. Factors such as insulation, local climate and local humidity can affect the recommended BTU size for your particular application.
Up to 325sf – 7,000 BTU’s
325sf – 425sf – 9,000 BTU’s
425sf – 600sf – 12,000 BTU’s
600sf – 750sf – 15,000 BTU’s
More than 750sf – Multiple PTAC units needed
If you buy a PTAC unit that is oversized for your rooms, the PTAC will quickly reach the desired temperature but will do less aire filtering of dust particles and less dehumidifying. If you buy a PTAC that is undersized for your rooms, the PTAC will run much more often than necessary.