The New England Geothermal Professional Association's professional members are focused on providing efficient and reliable geothermal heat pump systems throughout New England. Only when we work to identify and educate the end user on critical design and application processes can we protect best outcomes, and in turn, the continued growth of our industry here in the northeast. Application results can vary dramatically based on accurate calculation of building load, earth-coupling capacity, heat pump capacity /rated efficiency and understanding of critical pressure and temperature consideration throughout the design.
For this reason NEGPA has developed some important "touchpoints" we hope will inform residential and commercial building owners toward attaining best outcomes.
All reputable geothermal heat pump systems sold in the U.S.A. are rated using common, optimized testing parameters by AHRI (American Heating/Refrigeration Institute - www.ahridirectory.org ). These ratings are listed showing both open well and closed loop geo system performance ratings that were achieved and confirmed in the AHRI lab.
Examples of AHRI rating sheets:
In order to attain these performance metrics in your application, you must be sure to respect and maintain the same design and operation parameters specified and employed by AHRI in the lab.
That said there are several elements to consider in design.
- What is the actual heat loss of the building? Is that calculation based on the AVERAGE temperature in your town or the “mean extreme”? Was that calculation accurate? Was the data provided to do the heat loss calculation accurate?
- Do you intend to build/install a 100% solution or cover a fraction of the buildings heating/cooling requirements?
- Will you be maintaining set points used by AHRI when they rated the units?
It is not necessarily wrong to consider partial systems, or systems that do not ALWAYS operate at or above AHRI published efficiency, but it is certain that departing from those ideal test parameters AHRI used in identifying system performance will directly affect seasonal performance realized.
Following are a few of the primary design elements presented in relatively simple terms that we hope you will find helpful as you and your chosen application partners work from design to application of a winning geothermal investment.