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RESNET/ACCA Standard 310-2020 “Standard for Grading the Installation of HVAC Systems” 

07-10-2020 09:21 AM

This new ANSI standard sets the technical specifications for the inspection, testing, and labeling of a home’s HVAC system. Development of this standard was the culmination of a partnership between the Residential Energy Services Network (RESNET) and the Air Conditioning Contractors of America (ACCA)

The standard outlines five separate tasks to be performed by a HERS Rater to evaluate and grade aspects of the HVAC system’s installation and performance.  These tasks are non-intrusive or have minimal impact (make a hole for a static pressure probe).  Additionally, each task has an alternate compliance path that allows an independent verification report to provide the necessary information. 

The standard’s five tasks consist of two prerequisite tasks that must be passed before the process can continue, and three functions that contribute to the HERS / ERI score improvement.

  1. Prerequisite: HVAC System Design – Ensure the dwelling’s attributes are correctly modeled, and ensure the dwelling was built per the design. This looks at key contributors to the homes heat loss/gain, and confirms those elements are present as specified.   
  2. Prerequisite: Total Duct Leakage – confirm that the duct system is tight. Leaky ducts could mask problems that exhibit low static pressure and low fan watt draw.  However, the conditioned air could be leaking into unconditioned space where it does not promote comfort.
  3. Task: Airflow – Several different methods can be used to confirm that system airflow is within a tolerance of the design airflow.
  4. Task: Fan Watt / Cfm – This metric is not cited in the ACCA 5 QI Standard at this time; however, this metric reflects the duct system’s efficiency. A fan that uses less energy to move the design airflow is more desirable than a fan that must draw heavily to turn the fan to achieve the same airflow. 
  5. Task: Refrigerant Charge – The Rater takes a series of temperature measurements indoors, outdoors, and at the refrigerant lines. Or proof the weigh-in method was used is also accepted.

The critical question is, what will be the impact of the above standard on the HERS or ERI scores?  The calculations to determine the effect of these measurements are under development by another committee.  This standard focuses on forced-air cooling and heat pump heating; therefore, climates, which are cooling dominant or regions that use heat pumps, will see the potential to lower (improve) their HERS Index / ERI scores. 

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ANSIRESNETACCA_310-2020_v7.1.pdf   1.81MB   1 version
Uploaded - 07-10-2020