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Old 06-19-10, 10:14 AM   #11
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Default We may have reached 'lift-off'...

Regarding whether to use HRV (sensible heat recovery only) or ERV (sensible + latent heat recovery) I came across the above graphic that spells it out...

Originally Posted by Xringer View Post
I saw some HRV units on Ebay in the $450 range. Looked up the maker and found this HRV Airiva Heat Recovery Ventilator.
Interesting that it uses a Polypropylene core...

They show the core in the video, it looks to be the same kind of material that political yard signs are made of, cut into 10 to 12 inch squares, and glued together with the air channels in an 'alternating' orientation.

Since building the core seems to be the biggest snag in making a DIY HRV, we may have reached 'lift-off'.

A 90% or greater HRV is very difficult to achieve, the only one I have seen is an 'enthalpy wheel' design.

This ERV?s For You - Feature Articles - Extra Edition - Air Conditioning, Heating & Refrigeration NEWS

Enthalpy wheels and permeable (or enthalpic) plates recover temperature and humidity. Enthalpy wheels are the most popular and effective technology for commercial applications, particularly where outdoor air is a source of humidity and indoor humidity must be controlled.

In an enthalpy wheel, as the heat exchanger rotates from one airstream to the other, it transfers water molecules from the wetter to the drier side. In summer, the cool, dry surfaces of the heat exchanger strip heat and moisture from the entering outside air. In winter, those same, now relatively warm and moist surfaces heat and humidify the ventilation air.

In an enthalpic plate, water molecules are allowed to move through a membrane to transfer to the opposing airstream. Sharing some of the characteristics of enthalpy wheels, they generally are less efficient at transferring humidity and are more widely used in residential applications where outside air is a smaller percentage of the load.
Also, I came across a Ventilating Industry Test Proceedure used for certifying ERVs. May supply some interesting ideas for makers:

...and here's a Certified Product Directory, with efficiency ratings of various tested HRVs:


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Last edited by AC_Hacker; 06-19-10 at 11:43 AM.. Reason: Clarifying PIX...
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