Air return askew? used doublewide

[jack roscoe]

Newbie here. What little I know here I have learned in the last few days on the internet. But I've worked in several shipyard trades and have some background and fair mechanical ability.

I have a used doublewide and while replacing the air filter noticed something that may be a little out of order. Plus, the air in the sheetrock return box makes a loud whistling noise.

The sheet metal piece thingy mounted in the floor (the air filter is in the wall) is oval 10" x 16" at floor level and tapers down to round at 10" diameter. It goes straight down. I don't know what it is called.

Went underneath and a short 12" dia. straight piece is mounted/joined (taped) to the tapered piece above. Then there is 12" flex, then a 12/14 increaser/reducer, then 14" flex right to the package AC unit.

I think they used the 10 x 16 oval thingy because to get a 12 or 14 round collar in there they would have had take a torch to the steel frame or do a lot of grinding, dangerous and really messing up the insulation. imo this should just be left alone, as is. But I want to increase return air flow capacity and reduce friction.

So I want to put in a floor register with a filter and run flex to a tee in the 14" flex return duct underneath, sort of doubling the return capacity of what now exists. I'm thinking the new, added flex should be 12" or 14".

Could you please tell me what the stuff I need to buy is called, and walk me through the basic steps? Thank you.

I am able to find a location between joists and away from steel (I hope).

[Robert]

Hi,

That is something that can be tricky and also must be done correctly. The amount of return air must be correct as well.


Because this can cause more problems than wanted if done incorrectly, I would have an hvac tech come out and consult on size needed and best solution to accomplish it.


Then DIY accordingly. Not something that should be attempted from here without being there to see it.



Thanks,
Robert

[jack roscoe]

I'm wondering if you agree the original installation fifteen years ago was screwed up?

I can't imagine that the tapered thingy down to 10" dia. would be correct on a 14" return.

The AC tech who is installing the new AC already told me to replace the 10" supply flex (after a tee" with 14". He didn't look inside the return box however.

Said he hates going under but will do it for $75 per hour. I can definitely do that as I only make $11. He will be back when the new AC arrives and I have the ducting labor completed.

I would imagine the manufacturer screwed up the production drawings as the original cause of this problem. After fifteen years I doubt they could be held accountable. I'm going to live and let live and do the best can be done.

[Robert]

Hi,

I don't make install judgments that aren't mine without seeing it in person. That is a packaged unit install and would not have been done at the factory.

I would be sure of size needed and then go from there with a new location if needed in order for it to fit in the space.

That's the basics of it, do the Manual D duct sizing calculation to find correct size needed.


Then only install that size in a place where it fits.



Thanks,
Robert