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Selection & Sizing

The selection and sizing of the heat pump system require two things.

1. The building's heating and cooling loads and the domestic hot water heating requirements must be provided by the heat pump system.
   
2. An estimate must be made of the ground heat exchanger loads given the heat pump operating hours.

The steps to follow are:

1. Calculate the building's heating and cooling design loads using one of many alternative methods including:
   • Hand calculations based on ASHRAE recommendations.
     
   • Air Conditioning Contractors of America Manual J for single family detached homes , or
     
   • Manufacturer or other accepted computer software programs such as those available from Carrier, Right-J, WaterFurnace, and Trane, or from Oklahoma State University for multi-family and commercial applications.
2. Select a properly sized heat pump to serve these loads. This subject is discussed in more detail in the Heating and Cooling Equipment Sizing segment, and in equipment manufacturer's catalogs.
   
3. Select the type of indoor distribution system. An air system is typical for single family residential and some commercial and institutional applications. A water-to-air system is often considered for larger multi-zone commercial and institutional type buildings. In the latter case, the primary heat pump is a water-to-water unit, rather than the water-air type.
   
4. Size the indoor distribution system. There are a number of manuals and some software programs that can assist the distribution system designer.
   
5. Select the proper air supply and return diffusers, registers and grilles.
   
6. Estimate the building's energy requirements given:
   • The heating and cooling loads,
     
   • The type and size of heat pump equipment selected, and
     
   • The thermal characteristics of climate and soil.
7. Estimate the ground heat exchanger loads, considering the annual load and the design month's load.