Noisy vents and one noisy return

[1894House]

Any idea what would cause a few vents to be noisy (while some are perfectly quiet) and one return to be louder than the others?

Thanks!

[adrianf]

under sized duct/grills
unbalanced system

[the dangling wrangler]

Closet or attic install?

[1894House]

The quiet vents are the flex duct that are run in the eaves and the noisy ones are the rigid ducts. Also, the return that is noisy (almost like a hum) is very close the the air handler, should that make a difference?

[1894House]

attic install.

[Focko]

Some of them just resonate really nicely (badly). Aside from expanding the cross-section of the opening . . . what you can do is just take out the grille and put in a different one of the same size. Another thing you can do is take it off, stick foam tape on the back of it in the wider spots . . . but getting a new, different one is probably easiest.

[skippedover]

Air is stupid. It takes the path of least resistance. It's a known fact that metal ducts are inherently more efficient for airflow than flexible ducts. In fact, research has shown that the resistance to airflow through a flexible duct is significantly worse than originally thought. So if the initial velocity of air leaving the main trunk is, say 700 feet/minute, then it's probably more along the lines of 400 FPM by the time it gets to the end of a 15 or 20 foot flex run but 650 FPM when it gets to the end of a metal duct run. This is why upscale companies limit the amount of flex they'll use to 10 to 15 feet, while low bidders will run 25-foot length like spaghetti.

If you find that the noisy outlets are also the hottes rooms for heating or coolest rooms for cooling, then you've got some room to balance. On the other hand, if all the rooms are evenly heated and/or cooled, then the solutio is a little more complex. If a Manual 'J' load calc was done, an airflow hood is the best way to determine the best solution. But assuming for a minute that a noisy room is also over served; the solution is to have a balancing damper installed in that branch line at or near the main trunk. (There is a main trunk and not just a little short piece, right?) Partially closing down the balancing damper will decrease the velocity and the actual volume of air delivered to the room, thus quieting the noise and reducing the amount of heat or cool delivered. Of course, this means the 'rejected' air that used to flow through that branch supply is now seeking an alternate route. So proper design of the system is paramount. I was in a home today where we installed 3 geothermal heat pumps. The master bedroom I had operating on 2nd stage heat and honestly, you couldn't hear any noise from the airflow at all. Manual 'J', Manual 'D' design and installatiion. Not the low bid!! When it's done right, the results are just what you'd hoped for, pure comfort, no noise. When the job is cheaped (I want 3 bids) the results are something that get lived with for 100-years and never achieve any comfort.

[Buzzy]

Skippedover,

I love your tag line. "IF YOU THINK A REALLY GOOD TECH IS EXPENSIVE, YOU SHOULD TRY A REALLY BAD ONE! "

Truer words never spoken.

I don't want to over pay... But I am learning you get what you pay for...

Buzzy - Sears victim

p.s.

Anyone know a skilled, professional, HVAC guy/co. that takes pride in their work in Toronto/GTA?

[Focko]

When the job is cheaped (I want 3 bids) the results are something that get lived with for 100-years and never achieve any comfort.

Amen to that. Installation done right is well worth paying more for. The best equipment from the factory can be screwed up efficiency-wise and reliability-wise with crappy installation, not to mention the building not being comfortable.

Having installation done by a company with a good reputation and a fair amount of years in business is worth the extra $ it might cost.

[1894House]

I received 7 bids and the company that we went with was definitely not the low bidder. It's a family-owned company, in business for over 40 years, active in the community, good recommendations, etc. We spent A LOT of money on these systems and I am hoping that when the owner comes out later this week he will rectify the problems.

[rkgtech]

Air is stupid. It takes the path of least resistance. It's a known fact that metal ducts are inherently more efficient for airflow than flexible ducts. In fact, research has shown that the resistance to airflow through a flexible duct is significantly worse than originally thought. So if the initial velocity of air leaving the main trunk is, say 700 feet/minute, then it's probably more along the lines of 400 FPM by the time it gets to the end of a 15 or 20 foot flex run but 650 FPM when it gets to the end of a metal duct run. This is why upscale companies limit the amount of flex they'll use to 10 to 15 feet, while low bidders will run 25-foot length like spaghetti.

If you find that the noisy outlets are also the hottes rooms for heating or coolest rooms for cooling, then you've got some room to balance. On the other hand, if all the rooms are evenly heated and/or cooled, then the solutio is a little more complex. If a Manual 'J' load calc was done, an airflow hood is the best way to determine the best solution. But assuming for a minute that a noisy room is also over served; the solution is to have a balancing damper installed in that branch line at or near the main trunk. (There is a main trunk and not just a little short piece, right?) Partially closing down the balancing damper will decrease the velocity and the actual volume of air delivered to the room, thus quieting the noise and reducing the amount of heat or cool delivered. Of course, this means the 'rejected' air that used to flow through that branch supply is now seeking an alternate route. So proper design of the system is paramount. I was in a home today where we installed 3 geothermal heat pumps. The master bedroom I had operating on 2nd stage heat and honestly, you couldn't hear any noise from the airflow at all. Manual 'J', Manual 'D' design and installatiion. Not the low bid!! When it's done right, the results are just what you'd hoped for, pure comfort, no noise. When the job is cheaped (I want 3 bids) the results are something that get lived with for 100-years and never achieve any comfort.


OK, I am convinced that the above mentioned is my noise problem.
"If you find that the noisy outlets are also the hottes rooms for heating or coolest rooms for cooling, then you've got some room to balance."

The noise from the furnace is driving me crazy.. can you guys recommend a HVAC specialist or contractor in Brooklyn, NY that can work with York furnaces (to fix the noise) ?

Thanks

[UNOH1]

The duct size and or grill size may need to be looked at. Either the installer did not do a good job of sizing the duct correctly to compensate for the air velocity that is lost, or he didn't know what the hell he was doing.....have someone take a look at the duct runs from the vents that are noisy, and have him/her take a velocity reading from each vent to see how much is lost.


Hope this helps
:)

[rkgtech]

The duct size and or grill size may need to be looked at. Either the installer did not do a good job of sizing the duct correctly to compensate for the air velocity that is lost, or he didn't know what the hell he was doing.....have someone take a look at the duct runs from the vents that are noisy, and have him/her take a velocity reading from each vent to see how much is lost.


Hope this helps
:)

Thanks! yes it helps. The installer had first installed the furnace (hanging) in a small room in the mezzanine (fire proof door). There was duct work - initially - but it was SOOO loud that someone suggested to him to take the duct work out. once the duct work inside the room was removed, the noise was cut to half but even now it is VERY loud. the return grille is 24X24 and while on the phone with york, they claimed that it was good enough. It was a vertical unit that was installed horizontally. Now the vents closest to the supply are loud and heat up extremely well where as the branched off section (one room and the kitchen) barely get any heat and there is NO noise.

also weird enough, but if i shut the vents closest to the supply end - the unit trips and i have to reset it..