Comparing HVI and AHRI test results for ERVs
Jennifer_Martin
| Posted in Energy Efficiency and Durability on
Our project is trying to determine which ERV units will be most efficient for our application, and we’re looking at a variety of ERV products. Some are tested by HVI while others are certified by AHRI. We are struggling to accurately compare the difference between testing results offered by HVI and AHRI. There seems to be very little ability to cross-reference test results, making a comparison all but impossible. What techniques or systems have you found for comparing these two testing standards?
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Replies
Jennifer,
I look forward to reading the comments from GBA readers who are more familiar with protocols for testing residential ERVs than I am.
Most builders or architects who are interested in comparing ERV performance specs consult the ratings posted by the Home Ventilating Institute (HVI).
AHRI is a trade association representing manufacturers of heating, cooling, and commercial refrigeration equipment. I am not familiar with their ERV testing programs.
In general, HVI ratings apply to "residential" HRV/ERVs (typicaly under about 300cfm maximum airflow) and AHRI ratings apply to "commercial" units (typically 400cfm and over), though there is a bit of overlap for products in the 350-450cfm range. As far as I know, the laboratory testing used for HVI and AHRI ratings is very similar, however, how those testing results get reported in the respective rating databases is not.
Within the HVI ratings, the best way to compare product performance at the moment is to find the units that can meet your airflow requirements, then compare them by their SRE (sensible recovery efficiency) at (important!) the desired airflow. SRE is a combined efficiency rating that factors in heat transfer efficiency as well as fan motor efficiency. The best units have excellent heat transfer as well as very low power input. Do not be fooled by the ASE (apparent sensible effectiveness) ratings. The ASE is not a good measure of comparative product performance. Some systems have higher levels of exhaust air transfer ("cross leakage") and/or low efficiency fan motors, both of which lead to higher ASE numbers, but worse overall efficiency (SRE).
Unfortunately, the AHRI ratings are NOT as detailed as HVI. Specifically, the ratings do NOT include fan motor energy...I suspect this is due to the fact that these units are often customized for a particular application...a given HRV/ERV "core" and exterior case could be combined with a number of different fan options, depending on the airflow requirements. The best you can do at first is to compare products that meet your airflow requirements by looking at AHRI's "Net Effectiveness" ratings (sensible and latent, heating and cooling). See attached example. The "Net" ratings DO account for exhaust air transfer, however, they could potentially be "inflated" by low efficiency fan motors. Once you've narrowed it down a bit, you can start going to the manufacturers to try to track down what the fan motor efficiency would be for your particular application.
Thanks, John, for your helpful comments.