View Single Post
Old 06-29-10, 12:15 PM   #56
AC_Hacker
Supreme EcoRenovator
 
AC_Hacker's Avatar
 
Join Date: Mar 2009
Location: Portland, OR
Posts: 4,004
Thanks: 303
Thanked 723 Times in 534 Posts
Default 8 inch cube

Quote:
Originally Posted by Xringer View Post
Now, I just might wait to see how your DIY OFC (One Foot Cube) works out, before I start hacking my little 8" Cube..
I've been pouring over more literature, looking at cross-flow Heat Recovery Ventilators and their reported efficiencies. Here are some HRV's that use almost identical design concepts and are almost identical in size.


NOTE:
The Panasonic is different because it is a design meant for one modest room, and is designed to fit between ceiling joist spaces. This is of special interest to me because I have limited the amount of my house that I heat and cool.
(info here)
I think the brand-to-brand efficiencies should be cautiously compared because there are so many ways to 'enhance' test results, with the lower numbers shown probably being closer to reality.

But the variations within a brand are probably a reliable indicator. In that light I find it interesting that the lower the CFM, the higher the efficiency.

My house is pretty small to begin with, and I'm not heating/cooling the whole thing, so my heating/cooling bills have been laughably small. But, eco-minded tightwad such as I am, I'm constantly trying to beat it down even smaller.

So most of the HRV's on the chart above are meant to be used with a house of 1600 feet and above (up to 3500 sq ft) , which is how the American market usually lives. But my conditioned space is only about 600 sq ft, so with the exception of the Panasonic, even on the lowest setting, the HRV's are changing out air at twice the optimum rate for my house-space... I wouldn't even be able turn it down... only off.

I looked at the scale drawing of the Panasonic, in particular the core, and did a graphic divide across the length dimension and came up with the size of the core being 5.5 inches square. Pretty darn small. But the efficiency is pretty darn average...

Using the criteria supplied by mrd in a previous post,

Quote:
ASHRAE 62.2 is residential ventilation industry standard, and I believe the latest version stipulates 7.5CFM/occupant + 1CFM/100sqft
My house is small (600 sq ft) and single occupancy, so:

7.5CFM + 6CFM = 13.5CFM = minimum ventilation.

So I'm thinking that the core I am copying is really appropriate for a much bigger house (4x to 10x bigger), but if I am very careful in the selection of my fans and achieve a CFM of 15CFM minimum, my efficiency should be pretty favorable.

So Xringer depending on your conditioned house volume, your little 8 inch cube may not be so little after all...

-AC_Hacker
Attached Images
 

Last edited by AC_Hacker; 06-29-10 at 02:20 PM..
AC_Hacker is offline   Reply With Quote