Are there dampers near the supply plenum on the duct runs to balance airflow to the rooms? From what source are the 3 diffusers fed; from one duct run or more? The 3 diffusers maybe sized correctly when all three are used, otherwise the static drop may be too high. We would only be guessing from here. - udarrell Here is a link that might be useful: Air Side of Air Conditioning

They're selling snake oil. There are so manys thing wrong with this proposal. First off, why do you feel you're not getting enough airflow? Is the room they used for their demo hard to heat or cool? If the existing 370 cfm is enough to keep that room comfortable, then there is no reason to pay money to increase the airflow. "More" is not always better. Your air handling system was designed to move air as an enclosed system. OF COURSE it's gonna move more air if you rig it to operate with the fan cover door opened. But again, more is not always better. I'll bet you could stand in that back room and *hear* the air rushing and whistling out of that vent after they took the blower door off. Your system should be set up to move the required amount of air as quietly as possible. You're also risking damage to the blower by making such a drastic change to the static pressure. The fan is designed to work against some amount of resistance. Lessen or remove that resistance and you could burn your fan motor out. A return in the basement is going to bring extra humidty and musty odors into your home. The air conditioning unit would have to work harder to remove the extra humidity. It could actually cost *more* money to operate. And if the unit was not capable of removing the extra humidity, you end up with damp air in your living quarters. This results in a cold, clammy feel that makes you feel uncomfortable. If you have some rooms that are hard to heat or cool, have a reputable HVAC company *calculate* how much air needs to go to each room. It's not a guessing game, and more is not always better. I noticed that you called the original installers and they blew you off. Forget them, they don't sound very professional. Try asking some of your neighbors for referrals, or check something like "craig's list". There has to be a reputable company in your area.

I eventually had my HVAC guy come out and asked him. He said it was okay to partially block the heat vent, but if it had been the cold air return it would NOT have been okay. So I happily moved the frig to it's best place and moved the frig right up against it. So the heat vent is about halfway blocked and I just put one of those magnetic vent covers over the half behind the frig. I'm not an expert, but I think it helps to force more air out of the half that's not blocked. So, unlike most kitchen renovations, this cost me nothing. Yay!

Yes this house is pretty strange. Its an old farmhouse and when they put in the oil furnace (which we don't use) they just sort of slapped the registers here and there. We basically just stopped the cold air with batting and sealed it up with duck tape (neon pink). its already made quite a difference.