Once you’ve chosen a geothermal heat pump (GHP) as your home’s heating and cooling system, sizing it properly is the first step in the geothermal installation. Little about the process is do-it-yourself, and it’s critical you work closely with a trusted HVAC contractor to find the right size for the GHP and the underground loop field.
The contractor needs to perform a load calculation for your home. The industry tool to determine the load is called Manual J and it takes into account the many factors that contribute to its energy efficiency. In addition to the size of your home, these include:
- Insulation levels in the attic and walls;
- Number of windows, their efficiency and placement;
- Air infiltration levels;
- Number of heat-producing appliances under roof;
- Preferred indoor temperatures;
- Number of occupants and their ages;
- Cubic footage you need to condition; and
- Landscaping factors.
Once the contractor knows the system size, he or she can move to the second step of the geothermal installation. This involves the layout and volume of the ductwork using another tool called Manual D.
Because a GHP uses heat underground (via a loop field) instead of the air as the energy source, the contractor has to determine how big the loop field needs to be. This exercise also looks at the size of the GHP you need, along with the geology of your yard. Soil types and rocks make a difference in the ability of the loop field to collect or harvest heat.
Clay soils and rocks store more thermal energy, which means that your loop field can be smaller. Sandy soils, on the other hand, are less able to hold heat, requiring a larger loop field.
Careful sizing for the GHP, the ductwork and the loop field assures your satisfaction and indoor comfort with the system. Over-estimating the size results in short cycling, which increases energy bills and wear on the GHP. A system that’s too small won’t meet the conditioning load of your home, leaving you uncomfortable.
If you would like to learn more about a geothermal installation, please contact us at Bill Joplin’s Air Conditioning & Heating. We’ve provided HVAC services for McKinney, Frisco and Allen since 1978.
