Heat pump capacities

The Air Conditioning and Refrigeration Instititute-certified cooling capacity of heat pumps for ground source closed-loop use are published by the manufacturer in their catalogs. ARI ratings cover units rated below 135,000 BTUH at ARI standard cooling rating conditions. Units above 135,000 BTUH may be rated but these ratings are not certified.

The ARI Standard 325 certified cooling capacity of heat pumps for ground water-source use are published by the manufacturer in their catalogs. ARI ratings cover units rated below 135,000 BTUH at ARI standard cooling rating conditions. Units above 135,000 BTUH may be rated but these ratings are not certified.

These standards allow reasonable comparisons between manufacturer's models. They can be used as a basis for estimating energy use and annual cost to help the consumer make a "better value" decision.

Water-to-air heat pumps

Units are available in a number of configurations. Airflow is usually in the 400 cfm per ton range.

Because winter ground loop temperatures can drop below freezing, closed loop systems require extended rating designs.

• Configurations and nominal cooling ranges include:

• Vertical upflow air discharge from ¾ to 10 tons

• Vertical counterflow air discharge from one to six tons

• Horizontal ceiling mounted from ½ to 10 tons

• Duel compressor units in the above three categories

• Split systems (compressor/water heater exchangers and air handling sections) from 1-1/4 to five tons

• Large commercial vertical upflow air discharge from 10 to 30 tons

Other specialty extended rating designs available include:

• Two-speed units, horizontal and vertical from 2-1/2 to six tons

• Floor-mounted console units from ½ to 1-1/2 tons

• High-rise vertical units, pre-piped and wired, built-in or flush-mounted from ½ to three tons

• Large commercial vertical variable air volume units, rooftop packages from five to 25 tons

• Schoolroom unit ventilator units from two to four tons

Manufacturers offer a wide range of optional accessory items, including hot water generators, system controls, supplemental electric heat packages, dehumidification options, cupro-nickel water-to-refrigerant heat exchangers, hose kits, cabinet paint finishes, improved filters, sound attenuation packages and flow centers (loop pump modules).

Water-to-water heat pumps

These are typically single packages for indoor installation, usually floor or slab mounted, and are made in sizes from one to two nominal cooling tons and larger.

There is no practical upper limit and very large sizes use centrifugal compressors. Typically, these units can produce up to 130 degrees hot water.

Units in sizes over 10 tons and for over 130 degrees hot water are considered industrial heat pumps and are not covered.