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DIYMOM2012 07-30-2012 10:57 AM

Please Help! Returns & Ducting Problems
Hello Folks!

Hoping for a little help here :confused1:

We have a 1600sf single level home, part flat roof and part very high ceilings w/ very small attic space.

Our AC is a Trane XR12, our heating system is a Trane XL80.

We have 2 returns in the house: the one located closest to the heating unit is a 10in return from here 8in ducting is used and leads to a 8in return located in the hallway.

1. The first problem we have are that the noise level is crazy when we run

2. The second problem is that we get a musty smell when the unit is

We had a HVAC guy come out and he suggested changing both the returns and the connective duct to 16in. He said this should take care of the noise and of course the new ducting won't allow the attic air to be pulled into the new system. Funny thing is that when we go into the attic it doesn't smell like the musty air that the unit puts out.

Another HVAC guy we know says to go with 14in returns.

3. Third problem : I also asked him if he could change the size of the metal
box on the first return because the mouth is a odd size (8 X 22) and we
can't find Filtrete filters to fit it but he said that that is a major job and
he'd had to tear up the wall to that that.

We know nothing about HVAC at all so any guidance would be much appreciated!! Hope I provided enough info and sorry if I provided too much!

Doc Holliday 07-30-2012 12:46 PM

I charge $350.00-$400.00 to add/change a return filter grill. Not that big of a deal in any way. You shouldn't even need any sheetrock repair.

All it is is removing the existing filter grill, unframing it and re-framing to the size of the new one. Cut a bit of sheetrock so the base of the grill fits into the new framing, screw grill into framing and done. There's about a one inch lip all the way around the grill that covers the cut sheetrock so again, no need for any repairs. Hopefully the grill has a duct board backing but it's nothing at all to add a piece to the back, cut a hole in the backing for the new and bigger collar (for the new and bigger 14" or 16" return duct), seal it all with mastik and done deal.

25 x 20 is a common return grill size.

Entire job may take two, possibly three hours including new duct run.

Yes, your return air ducts (and grills) might be too small if the noise is too loud to bare. If those filters are sucking up into the grill really hard it's another tell tale sign of needing to increase return ducts.

Think of it like sucking as hard as you can through a tiny coffee straw. Your system is not receiving enough air to satisfy proper heat extraction with too small return ducts. Have that taken care of and not only will the noise be reduced but you'll notice a difference in comfort.

REP 07-30-2012 02:20 PM

Since you dfidn't tell us what size a/c you have or what part of the country you are living in,we can't suggest what size duct you need.
All I can say is what you have now is way way too small and that too big is a very rare installation.Its much better to be too big especially if you have flex duct.
Quality homes have a return in every room except the kitchen and bathrooms.This gives you the quality comfort in each room.
What you have if sized right will give your equipment the right amount of air flow but you will notice a bit of discomfort in every room.
Ther low bidder for the equipment in your house did not do your house any favors.All they did was save themselves some labor .

turnermech 07-30-2012 05:04 PM

14"= up to 2.5 tons
16"= close to 4 tons

does not mater where you live.

DIYMOM2012 07-30-2012 11:52 PM

My AC is 4 tons.

Thank you all for your input so far.

scottmcd9999 07-31-2012 06:25 AM

If your measurements are accurate, your returns are waaaaay too small. As others have suggested, 16" would be much preferred over 14". With returns, bigger is always better.

I too agree that changing a filter grill is generally no big issue, but if the return is metal duct to the return box, and the return grill fits that duct exactly (which is the way it sounds) then changing the filter grill size can be a bit of a challenge. Might be easier and cheaper to just buy filters from the local HVAC supply house - they would be able to source 8 X 22 filters (which is an odd size) for you, I'd assume.

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