Originally Posted by
Shophound
Addressing your point above in bold, you're on the right track. If your existing return air inlet is undersized for your unit, increasing the inlet size will reduce the velocity of the air entering the unit. Will it increase the volume of air entering the unit (which is what you're really after, since effective dehumidification and cooling of a building depends on sufficient turnover of the volume of air contained in the building)? That depends. If your supply ducts are restrictive and poorly installed, any increase in return air size, while netting perhaps a decrease in velocity, may not yet yield sufficient volume.
Why? Imagine this. You have a section of garden hose about four feet long. You stick your mouth over one end and blow air through the hose. You feel air exit the opposite side. You then think "I wonder if I can get more air through the hose if I make the end I'm blowing air into larger?". So you do it. You make a funnel that you can still fit your mouth around, stick it into one end of the hose (without actually reducing the area of that end's opening), and blow into it. You then find it's just as hard to blow into the hose as before, and you don't get any more air out of it than before. You may feel like less air is rushing out of your mouth and into the hose, but all you have done is reduced the speed of the air exiting your lungs and entering the hose, not the volume. The resistance the four feet of hose is still the same. Decrease the resistance by making the hose larger in diameter, and it suddenly becomes easier to move air through it. And you can ditch the funnel.
All that said, if your supply ducts are sized properly (iffy), then increasing the return size by itself may bring you some relief. However, if your system is oversized for the heat load of your house, you will still not be happy with your comfort, I believe.
Sorry, I must dissagree with you on your air velocity story. Restricting the air return slows the air flow through the air handler and through the cooling coil. He is not changing the demonsion of the coil or the supply duct around it. If the coil was in the return opening, there could be something to the velocity thing. The amount of moisture removed by a given coil with a specific cooling capacity is dependent on the amount of air flowing through the coil. Any enlargement in the ducts, return or supply will increase the air flow. An increase in air flow will raise the coiling coil temperature. Raised coil temps remove more sensible heat and less latent heat. Make sense??
Regards TB
Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
Use +Merv 10 air filter. -Don't forget the "Golden Rule"