flex duct sizing


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Old 04-16-06, 05:28 PM
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flex duct sizing

Hi guys, wondering if theres a considerable difference in air flow from the 10 inch flex duct to the 12 inch flex duct, doing a self contained packaged unit on a friends mobile home. his previous flex is 10 inch should i keep it 10 inch. or go with 12 thanx.
 
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Old 04-16-06, 05:57 PM
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lester,

air flow though a duct is sort of like water in a hose, reduce the size you have more pressure less volume, increase the size, more volume less pressure, i would go with what was designed for the system 10 inch. let us know how the project goes, you will help many.

barry
 
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Old 04-16-06, 06:31 PM
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Flex size

Use no smaller duct than the size of the inlet/outlet on the unit.
If you want to come off (for example) with a 12 then split it into 2-10" ducts, that's fine, but if the fittings on the unit are
12", don't use a single 10" duct.
 
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Old 04-20-06, 03:09 PM
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re

i got this job done , went smoothly i used a 90 degree galv elbow on the bend going into the home. so i wouldnt have to bent the flex duct to much. i used 10 inch flex. the return air is probly 3-4 feet long and the supply feed going into the home is probly 7-8 feet long. it seems to blow pretty good out all the vents. just as good as or better then the furnace.i was noticing most all his registers are along the outer walls why is that ? in the front and rear bedrooms there in the middle of the room.the main junction box runs the whole length of the trailer the way it looks. and the register supplys are feeding off that. the home is probly 900-1000 sq feet. and he has 9 or 10 registers. he wanted to know if i could add 2 registers one in his kitchen and one in the living area in the middle like the bedrooms running off the main junction box that runs the length of the trailer, just cut thro the floor and add them there like the others . what do u guys think ?
 
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Old 04-21-06, 07:27 AM
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In the old days the thought was to pull the cold return from the outside walls and feed the conditioned air at the inside walls. After many years of testing the opposite was found to work much more efficiently.
 
 

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