AHRI has recently approached the U.S. Department of Energy (DOE) to discuss findings of an AHRI internal review of test results for modulating boilers under its Certification Program for residential boilers. The internal review revealed that current DOE efficiency test procedures may result in inaccurate AFUE measurements for condensing gas boilers that are designed to operate at more than a single input rate, (i.e., two-stage or modulating condensing boilers.
AHRI will take the following steps to address the issue and develop a solution. These include:
• Requiring heat-up and cool-down testing for condensing, modulating equipment for qualification and verification testing, even if the model’s AFUE is not required to perform heat-up and cool-down testing
• Requiring manufacturers of all existing models in this subcategory of boilers listed in the AHRI Directory of Certified Products Performance to do one of the following:
— Drop the rating to 90%;
— Discontinue the model; or
— Provide test results, which include the heat-up and cool-down tests that support a higher rating
AHRI will provide DOE with an AFUE calculation for two-stage and modulating condensing boilers and request and expedited review and adoption. One such alternative calculation is accepted and the manufacturers provide new test data, the ratings for those models with 90% AFUE listings and discontinued models will be restored with revised ratings as appropriate.