Energy Recovery Units and HRV's

[Guest guest]

I'm looking at HRV's and ERV'S and found this, that looks impressive with a

built in hepa filter. However I don't understand how you can pull in 'fresh

air' at the same spot that you exhaust it out. Does anyone have an explanation

for how this works.

If you are exhausting out air right next to where you are pulling fresh air in,

seems you would be pulling the exhausted air back in!

http://www.amazon.com/Broan-GSHH3K-Filtration-Ventilation-Recovery/dp/B00155U4BE\

/ref=pd_sim_sbs_hi_6

[Guest guest]

Barb

The air is exhausted at high velocity in the center of the combined intake/exhaust fitting and the air coming in is brought in from closer to the house, at low velocity; in no-wind conditions, that exhaust flow starts to mix with the outdoor air but that mixing occurs at a fair distance from the house.

In windy conditions where there is a sideways component to the wind past the fitting the exhaust flow is largely swept downwind of the fitting and little, if any, of the exhaust stays around long enough to be drawn in.

Under the unusual circumstances were the wind is directly against the fitting, a poor fitting design will allow some mixing and entrainment of the exhaust into the intake flow. That has been reported but I am unaware of how bad the re-entrainment really is. Normally it would not occur often, unless you aimed the exhaust directly into the normal wind direction.

Even with separate intake and exhaust fittings there are conditions where the exhaust air is partly re-ingested and some degradation of the intake flow is to be expected. Remember, however, that the exhaust air is roughly the same contamination level as what you breathe indoors so we are not talking a big deal here; we do not have tools to do anything perfectly, even when we think that is what we deserve and need.

Jim H. White SSC

Energy Recovery Units and HRV's

I'm looking at HRV's and ERV'S and found this, that looks impressive with a built in hepa filter. However I don't understand how you can pull in 'fresh air' at the same spot that you exhaust it out. Does anyone have an explanation for how this works. If you are exhausting out air right next to where you are pulling fresh air in, seems you would be pulling the exhausted air back in!http://www.amazon.com/Broan-GSHH3K-Filtration-Ventilation-Recovery/dp/B00155U4BE/ref=pd_sim_sbs_hi_6