HRV SRE and Efficacy ratings
I was about to purchase a LifeBreath HRV when I found the articles “Six Steps to Success with Heat Recovery Ventilation” and “Proper Integration of HRV into Air Handler Systems” (great articles), after reading the articles I am confused.
The articles state that the HRV’s SRE should be => than 80% and the System Efficacy (NET CFM /wats) should be => than 1.25, and that the HVI Institute publishes a spreadsheet that can be used to evaluate the available HRV’s. I downloaded the spreadsheet and began sorting and filtering the data and in the end there are only 6 out of 272 HRV’s that meet the above requirements, unfortunately in my area (NW PA) none of the 6 are available.
So my questions are:
– In the overall selection process what is more important SRE or Efficacy ?
– A lot of the major HRV’s listed have an SRE of 75%, is75% a published goal for HVI and Energy Star certifications and that is what most manufactures shoot for or is some other reason only 6 units make the cut?
– Some of the units offer ECM motors but the PSC versions of the same unit have better SRE and Efficacy ratings, I thought ECM motors were supposed to offer significant energy savings?
Thanks for any insight.
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SRE is what matters. CFM/watt (maybe system efficacy is a real term, but I've never heard it before) is nearly pointless, unless you plan to use the HRV as a circulation fan. The power the fan uses is accounted for in the SRE. 80% is a pretty high bar, and as such it's probably not realistic to use as a minimum cutoff.
From what I've read, the benefit of ECM motors is their ability to operate at different speeds without losing efficiency. Quite often, HRV / ERV specs are reported at a single setting (the one at which it shows the best number). That might be part of the explanation, but I'm just guessing. Maybe a good question to ask Lifebreath.
Since the fan uses electricity and the HRV recovers heat from who knows what source, you can't do an accurate cost analysis with them lumped together (other than resistance heat).
That's a good point I hadn't taken into consideration. Comparing becomes pretty complicated with that in mind. I would think that as long as the cfm / watts are similar, the SRE would be the more important spec. The cfm / watt is also affected by more external factors such as filter rating, developed duct length, etc.
I agree, the fan use should be a relatively small energy issue.
Thank You for the replies. As noted in my OP, researching just about everything related to ventilation/energy efficiency seems almost futile, there doesn't seem to be any standard reporting criteria or consensus on testing standards. Thankfully there are forums like this that can shed some light on real life expectations.