DIY ventilation heat exchanger

[Daox]

Any updates?

[AC_Hacker]

Originally Posted by Daox

Any updates?

Yes, I'm about 1.5 weeks away from having my bathroom remodel done, and sanitation functionality restored.

-AC_Hacker

[Daox]

woohoo

[Drake]

Don't know if anyones coroplast stacking is yet completed but might not cutting some 1" wide spacers to be used to separate cross layer giving you just one layer of separation over most of the area. Strips could be stapled(construction hand staple gun) in place until "core" can be placed in a custom mechanical compression form(from your pics of cross flow box line up corners with air flow dividers and and have "bottom" and "top" of box "press" core together when assembled. As not sure how well or how long(possible rusting) staples would last.

Always been interested in the theory HRV/ERV but living in a climate with several months of sub zero heating days effectively resolving "frost up" still isn't evident to me.
Heat pump xfer seems intriguing but won't it need a fairly large amount of in/out going air? I am exploring maitaining indoor air quality in my SI passive addition by minimizing VOC's, lifestyle, low temp solar fresh air preheaters(daytime) and still researching where I might recover some heat at night or just use small amount of direct ventln. Of coarse greatly reduced cost of DIY HRV system would make it more advantageous.

[Piwoslaw]

Here is a picture of the DIY countercurrent HX (see post #3) in place:

On the right is the bypass, even more to the right is the box that houses filters and fans.

[AC_Hacker]

Originally Posted by Piwoslaw

Here is a picture of the DIY countercurrent HX

Piwoslaw,

Is this a unit you built?

Please share more details.

-AC_Hacker

[Piwoslaw]

Originally Posted by AC_Hacker

Piwoslaw,

Is this a unit you built?

Please share more details.

No, unfortunately This is from a thread on a Polish builders' forum. You can try to decipher its Google translation. The thread is VERY informative, but there is also a lot of it, most of it noise. I sifted through it and posted most of the good stuff earlier in this thread.

[Ko_deZ]

Just poking my head in here too. This cross heat recovery unit has a major drawback. It sends moist air out, and dry air in. With a rotating wheel you will condense the moisture from the outgoing air, and evaporate it to the ingoing air, so you keep a decent humidity level indoors. Also, this helps against the unit freezing up. If only the outgoing air is dehumidified, there will be a build up of water, which might freeze if the outdoor temperature is cold enough. We regularly have -20 here, so even the wheel based models have some issues. My unit is made by ener(.no), and they have two large aluminium fins and a 3 way air walve that directs incoming and outgoing air back and forth between them. To my mind this should work better when it is really cold, as the hot and cold side will alternate. Also, the unit should be somthing like 93% efficient when running in low mode.

-Ko_deZ-

[Drake]

I have only found large commercial "wheel" ERV's in the US. Anyone know of a "residential" sizes one? Ko deZ what is the brand name? 93% of what? How can two passing air flows do more than reach equilibrium? The same with relative humidity of the air flows. Without a HP extracting it.

[Piwoslaw]

Originally Posted by Drake

How can two passing air flows do more than reach equilibrium? The same with relative humidity of the air flows. Without a HP extracting it.

If the angle between the two airflows is perpendicular or less (ie they are going in the same direction) then you are correct. But in a countercurrent HX it is possible extract much more heat: Imagine air (or any other gas or liquid) in the cold intake - when it enters the HX it starts to collect heat from the 'hot' side (which at this point is barely 'warm', since it is already leaving the HX having given up most of its heat). As the 'cold' air makes its way through the HX the 'hot' side is getting warmer, so it still has heat to give up. The 'cold' air exits the HX where the 'hot' air enters, ie where the 'hot' side's temperature is highest.