Airflow / cold air return

[robroy]

I have a new home with a Carrier Infinity 96 gas furnace and I'm concerned about improper airflow. For the supply, people tell me that on HIGH, it should be enough to really blow your hair noticeably -- mine doesn't out of any register. For the return, I did the "paper test" by placing a piece of paper over the return register - some have some suction but not enough to hold the paper fixed, some have NO suction whatsoever !! Are these tests enough to go back to my contractor with? What "rule of thumb" tests can I use to determine if I have adequate airflow in/out of my supply/return registers ?? ...something I can take to my HVAC contractor! Thanks!

[coco]

hope u have clean filters, start by reaching hand in register to see if a damper is closed inside the run. returns wont be dampered. probly just a bad run, not smooth, sharp bends etc. if u have access to duct make sure those returns didnt become disconnected. possible inside a/c coil packed w dirt?

[robroy]

Yes, I've covered off all the obvious stuff. Actually, I've tried to tune the ducts/airflow through the use of dampers, without much noticeable success in airflow / home comfort levels.

[docholiday]

As for the system, it cares only about what airflow is going through the unit. A properly designed duct system is another thing. You may simply have oversized ducts. I have never heard of a system that is supposed to blow your hair in a home. Where I come from that would be a problem. Did a contractor tell you this?

My first question would be is the home comfortable and then is the home evenly cooled and heated. If so, then I wouldnt mess with the system. If it isnt, then maybe it should be examined.

[bryancorfu]

I read in a text book from school, that if sytem is installed correctly you shouldn't know its running. The theory is that you wont haer or feel air movement when sytem is on. It will bring house to temp. without you knowing its even on. If your house is staying at your desired temp, then I wouldnt be concerned about how much air is coming out of registers. If its not coming down to temp. then theres a problem.

[bryancorfu]

You would also know if airflow is noy enough, if your evaperator starts to freeze up. After system is running for a while, check large line with insulation on it, and see if it has a coat of frost on it where it enters your evaperator.

[Irishmist]

This is exactly why you don't see any bald techs. The h"air"flow technique for determining proper air distribution is a tried and true method. This is why your very best service techs have a full flowing mane of hair. NOT.

[davidr]

Originally posted by bryancorfu
You would also know if airflow is noy enough, if your evaperator starts to freeze up. After system is running for a while, check large line with insulation on it, and see if it has a coat of frost on it where it enters your evaperator.

I would not depend on this as a test to determine if airflow was low.

[bryancorfu]

Thenks for that link, davidr. I just started in this field and am going by what Ive learned s far. Any info or new reading material is appreciated.

[robroy]

Sure, the system adjusts to set the temperature according to the location where the thermostat is, but this hardly is satisfactory if there are large gradients throughout the home. THIS, HOWEVER, IS NOT REALLY ABOUT TEMPERATURE, but rather achieving the recommended # of air exchanges throughout each room of the house (perhaps I should have posted this to Indoor Air Quality forum ..Ooops!). Thanks!

[davidr]

bryan,NCI has some great downloads on how to measure & interpret static pressure readings.
This is the best way to determine a fans airflow.

[robroy]

One thing I do notice is that the original installer definitely uses a lot of the joist work to channel the return air flow -- I thought this was not allowed i.e. building code does not allow use of building structure (???) since it is not intended to provide a proper air seal.

[robroy]

Originally posted by bryancorfu
I read in a text book from school, that if sytem is installed correctly you shouldn't know its running. The theory is that you wont haer or feel air movement when sytem is on.

Who wrote this textbook? Come on ... with my fan on at any speed, I certainly expect to be able to feel airflow coming from the registers. But I agree about the hearing part ... the Infinity 96 is quiet for the most part -- better be since it's supposed to be the quietest furnace on the planet!