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Flex for elbows?

2K views 9 replies 5 participants last post by  beenthere 
#1 ·
Hello,

I am installing a new hvac system, and redoing trunk and duct work to be properly sized. I am using round duct for my chutes to the vents (these will all be straight shots between trunk and vent), and I am going to have a lot of 90 elbows to buy. Our trunk sits below ceiling joists, vent chutes sit in side joists, so each vent will require 2 elbows. That adds up fast.

Question is, can I use flex to make my elbows, or do I really need to buy the expensive (well, relatively expensive) adjustable elbows? Any thoughts on this would be greatly appreciated.

Thanks.
 
#4 ·
The trunk will be rectangle.

I would use the top take off but they appear to be even more expensive than the elbows. About 90% of this I am doing myself with prefab sheet metal. (note, the plan was to hold off another year to get other bills paid down but we have a sick relative coming to live with us and I have to get it done, and on a lower than should be budget).

A couple years ago I bought a stainless steel flue liner for our chimney for a wood stove. I have about 15' of it left. I think I could cut into 1' pieces to make some of my elbows and use a crimp tool on the 6" ducts to insert into.

Does stainless and galvanized work well together, or is it a bad to have them touch each other?

Thanks, again. Any other thoughts would be greatly appreciated.
 
#5 ·
They cost more. But they will provide better air flow. With the way you want to do it. You would need to increase the size of the run to get the same air flow. Are you going to use a start collar, or a side take off on the trunk?

The chimney liner will be just as restrictive as flex.
 
#6 ·
Was planning on using a collar for the elbows. However, I've had a couple other guys come out to the house and work with me and I've actually been able to reduce some costs in other areas, so now I am really leaning towards the top take offs that you suggested. :thumbup:

Thanks for you posts! :thumbsup:

Oh, one other question, where can you buy mastic locally? Can't find it at home centers, can get it online but I am ready to start now!!! :)

Thanks
 
#9 ·
#10 ·
Flex will be very restrictive. Flex is fine as a duct, when you run it.
But, it must be stretched, or it restricts too much. The money the ells cost you. Will be saved in the operating cost of teh system, by better air flow.
 
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