return air drop for high efficiency gas furnace
Does it matter what type of return air drop I used when I install a new high energy efficiency gas furnace(95%)? Do I reused my old one installed 18 yrs ago. I plan to get a filter rack. The duct work used was not customized; just used stock duct work. I see that there are return air assembly where the boot is curved and some are slanted. Mine is just "L" shaped. One dealer said it matters and another said it doesn't whether you use curved or slanted, but appears to matter. The one that said it matters said that a curved boot provides less turbulence.
I read on one duct work dealers site the following: "High efficiency right angle filter assemblies allow the installer to offer a 20" X 20" X 5" filter cabinet with a furnace cut out dimension of only 14" X 23". The filter is positioned in a drawer at an angle. Reversing panels allow for left or right handed installation."
So does it matter?
Sizing is more Important
The size is the most important, but dealer that tells about better flow with radius boot or turning vanes is right. Small but their is a difference. They should have enough free area space, either 1 side of furnace or 2 sides or maybe even come through bottom of furnace is the best. Depends on amount of CFMs required.
Do it right the first time.
Slight difference. I've seen return drops with turning vanes so caked up with crap, that all it did was restrict more airflow....just like a blower wheel gets caked when there's no filter.
The key is as long as the duct work is sized right...period.
I installed a whole new system in my house complete with duct work. I put in a variable speed furnace with a 16x25x5 media air cleaner and a straight return drop properly sized...the filter gets equally dirty through out. The only difference is that I keep an eye out on it and change it when it's time.
This furnace may also move more air than old reliable,something to consider.
Would check sizing,if need to change,good time to go with curve and or turning vanes.
Media air cleaner
Thanks for replying. Question: The furnace I'm getting has a variable speed motor(an ECM). The dealer recommended a media air cleaner. Is that a better way to filter than just going with a standard filter rack and standard filter that I replace monthly?
Originally Posted by 2hot2coolme
Last edited by wsimpson; 03-31-2009 at 09:08 PM.
Reason: forgot to include my username
Originally Posted by wsimpson
your variable setup will likely perform its role better and be longer lasting.
How do I know if it's sized right?
One dealer said the return air drop is the correct size and another said it needs to be bigger slightly bigger and that's when the discussion turned to one dealer recommending a curved boot and another saying what you have is fine. So who's right since the dealer who may be selling me on something that won't improve air flow is getting my money.
Originally Posted by 2hot2coolme
If it cost me an extra $ for a new return air assembly, I could spend that on a media air cleaner. Can I calculate the CFMs myself and use that to determine the size duct of the return air drop? Do I include hallways, or just bedrms, bathrms, and living spaces?
Thanks again! WSimpson
No prices in post
Last edited by beenthere; 03-31-2009 at 10:37 PM.
Reason: Removed price
But, most times, the one saying the return drop is fine. Is trying to sell you on price.
Not on quality.