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peso 05-28-2008 04:45 PM

replacing rectangular duct with 6" pipes
I currently have an "extended plenum system" with one large rectangular duct (24"x6", 25' long) and 4 6" pipes branching off. I want to replace the rectangular duct and just go with flexible 6" pipes the whole way because the rectangular duct is large and taking up valuable headroom whereas it will be possible to more or less hide the pipes. Will this result in significant reduction in airflow? Is there a rule of thumb for how long you can go with a 6" pipe?

peso 05-28-2008 04:51 PM

Actually, they don't have to be flexible, they can be regular metal pipes if that's better. They would just need a couple 45 degree elbows.

8 Ball 05-31-2008 09:36 AM

Not a good idea to remove the branch duct 24x6.

Yes it will effect air flow.

15ft is normaly the max for flex duct.

In order to achieve the same velocity and volume, you would have to start out with a larger diameter duct...more loss of headroom.

Again...not a good idea.

coolmen 06-01-2008 08:05 AM

removeing the main trunk and bring all pipes to the plenum above the furnace is a bad idea. we call this a octapuss design, usally designed by some HACK. depending on how long the 6" runs are you will have uneven flow. get a pro to come in to see how best to fix your problem.

ro9beam2002 06-05-2008 08:43 PM


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