Concerned about duct install

[roccol]

I just had my 1st floor ducts replaced(old one were 60 years old). I have a 2 ton Lennox system(1900 Sqft 1st level, seperate system on level 2), the central return is 26 X 8 rectangle metal duct. About a 20 foot run with one 90 deg turn. The return floor opening is 30 x 8. Is this enough or should I have an additional return installed? Currently I wouldn't say the return is loud, but it is certainly not quiet Thanks.

[bobb25]

If it was a contract job, what did your contract specify? Did they replace the ducts with the same size, or was the old return duct 30 x 8? If the old return was 26 x 8, was it making noise before. The return duct capacity should be equal to or greater than the supply ducts. What did your contractor say?

[roccol]

This is all new duct work. The contractor stated he would have liked it a little bigger, but there are many design limitations(old house). He replaced ducts based on calculations(room sizes, windows, furnace siz etc.) The old setup had returns in every room. It was a very messy arrangement that did not work well at all. So it was not noisy, because half of it leaked in the basement. My basement is much colder with the new ducts. The new ducts are all larger then their predecessors.

[bobb25]

For a very rough comparison, compare the combined surface area of your old ducts to the new duct (8 x 26 = 208 sq. in.) No matter what, the return size should be equal to or greater than the supply duct. Call the guy who did the installation and ask him about the noise.

[2old2rock]

Can't understand why he would eliminate returns in each room. Except of course, kitchen and baths.

[tunnel_rat]

Can't understand why he would eliminate returns in each room. Except of course, kitchen and baths.

Ditto...inspectors here like returns in all BR'S.

[roccol]

If you saw the architecture of the home, you would understand why. Every hvac
contractor who came recommend a central return due to the home layout. Just because each room previously had a return, doesn't mean they actually worked well. Besides there is only 1 bedroom on floor 1.

One thing I do know is that the heat on floor 1 is now uniform across the entire floor. Every room feels the same more a less with the exception of the hallway where the return is (a little cooler as there is no vent in there). This was not the case prior to the new install. If I need to add another return, I will.

[tinknocker service tech]

IMO a 30x8 return grate or grille is a little light. I would add another one to give the system more return air and make it quite

If this grille is in the wall it is definately light

[roccol]

Grille is in the floor not wall. Goes into a good deep box.

[tinknocker service tech]

Grille is in the floor not wall. Goes into a good deep box.

Tis does allow for more air return but the face surface it design for a certain amount of air and IMO you should concider butting in another return somewhere to give plenty of return.

even though it is working ok for heat but noisey doesnt mean it is enough for ac and will be even louder when the blower is in high speed.

[roccol]

Sounds reasonable. How much more should I look to add(minimum)? They are not fully paid yet and have some other things to correct. How many CFM does a 26 x 8 duct carry(416?)?

[bobb25]

If every contractor recommend a 26 x 8 central return, and you have better air flow now, then you did the right thing for heating. I just wonder why there’s no large return on the 2nd floor also, especially for cooling.

Is it a loud bang when the system starts and stops, or more of a whistling sound?

[bobb25]

Your return duct should carry ROUGHLY 1100 to 1200 CFM. Your return grill is rated at ROUGHLY (depending on velocity) 600 to 1000 FPM. Try removing your return air grill and see if the noise goes away.