whiny furnace vents

[dalangdon]

Ever since we replaced the original forced air furnace in the house with a high efficiency one, the vent cover by my side of the bed has had a sort of high-pitched whine, like it is vibrating at a high frequency or something. This never happened with the old furnce, but the old furnace didn't have as strong of a fan on it.

I know it's the vent cover, because I took it off, and it stopped. Has anyone ever experienced this? Do we need new vent covers? I've only noticed it on the one in this particular room. Since it's directly above the furnace, I suppose it bears the brunt of the fan.

 

[alr2903]

yes indeed

try swapping it with one from somewhere else in the house. We had one in the bedroom exactly as you describe with terrific Force on it, and it whistled and the horizontal metal strips, the ones that louver up or down to close the vent, screeched and also rattled. we never close this vent anyway so i just used tin snips and cut the horizontals completely out, the front verticals for side to side are still there. It did stop the noise. i hear you though, the one we had about drove me nuts. alr203

 

[Cybrvanr]

check your HVAC unit too, you can turn the fan speed down in many of the units. It really won't sacrifice efficiency that much, but may save your sanity. My Trane heat pump has a 3 speed fan on it. My HVAC tech said that during the summer the big diff is that the lower speed de-humidifies better becasue the coil tempis lower, but the air does not get distributed as good. He also said that the lower speed in heat-pump mode puts out warmer air, but less of it, so it balances out

 

[exploder3211]

The ones in my old place did that esp. ones near the unit... They where on the celing, screwed up and all... I wound up replacing them with wooden ones to no avail and then when the HVAC tech came out and had a lookie he turned down the speed on mine and voila! No more noisy vents

 

[toggleswitch]

Agreed, I'd say it's the furnace fan speed being faster than it was.

Try opening or closing the vent a bit. Or gettimg one of a different air-distribution pattern.

When the air plenums / main-ducts are of fiberglass, no isolation mounts are needed. However if you have rigid metal ducts, a better installation will include not ONE but TWO isolation mounts [one on the supply air side and one on the return-air side] where there is a canvas-like piece of fabric in the middle of two metal duct pieces. This prevents vibrations from being carried through and amplified by the ducts.

Hope this helps.

 

[whirlcool]

In our last house we had the entire HVAC system replaced with an ultra efficient unit. With the old system, the air just kind of radiated out of the vents, with the new system it sounded like a hurricane of air coming from those vents. The HVAC tech went around the house using a rather long screwdriver and pried open the grill fins a little further apart. The noise went away and the house really could cool down fast after that.

 

[dalangdon]

Thanks for all the great advice!

It's good to know it's not just me who has noticed this sort of thing ;-) It used to not bother me that much, but it's been so cold in Seattle the last week or so that the furnace has been running a lot more than it did previously.

 

[sudsmaster]

Another thing you might try is balancing the duct system. Most furnace ducting has dampers in each leg, so that some can be restricted a bit to give the others more pressure. The damper is usually signalled by a small lever on top of the ductwork. The lever generally indicates the direction of the damper. Parallel to the duct run, it's full open. Perpendicular, it's as closed as it can be (not a good idea anyway). Usually just turning one partially closed will do the trick.

 

[whirlcool]

When HVAC installers replace a system, they are susposed to balance it. As Sudsmaster has pointed out, a balanced duct system can make a world of difference making sure each room in the house heats and cools evenly.

BTW, on my earlier advice, the installer used a screwdriver to increase the angle of each vent grill on each register. Doing this there was more "open space" between the bars for air to come out. The registers didn't look that much different than they originally did.