What causes an odor to come from only 2 vents in a HVAC system in a house.?

Question

16 Seer Trane heat pump installed 15 months ago. No odor until November 2005. Only in 2 vents. System has 2 speed fan that runs continuously. Only smell the odor when fan kicks into high speed. All vents were cleaned about 18 months ago. Installers said system was extremely clean. System has 4" thick filter (changed 3 times a year) and filters installed in all intakes(these are changed every month. Odor smells like sour mud. House is 2 story, no vents in attic. System is in basement. 2 smelly vents on the main floor at one end of a room. HELP ME!

The smelly vents are in the Living Room in front of a sunny window (South side). When the new system was installed they cut the Plenum and installed a sleeve made of what looks like rubber. It is not aligned exactly. COuld this low spot be the problem? It is about 9" from the main vertical trunk.

Has anyone else had this problem with a TRANE 16i Heat Pump? You can't see the pan under the coils.The vents are in the floor on the main level which is over a full basement. Keep the answers coming please.

The drain line empties into a floor drain.

Answer 1

Most HVAC ducting systems are like a tree.

Starting from the furnace/AC unit, there is a plenum (sheet metal box) from which all the main branch ducts are connected.

Away from the plenum, each branch goes off to a few rooms, and makes more branches to the actual vents.

It is most likely that you have an odor-causing problem at one of the branches connected to the 2 smelly vents.

Since you have a basement, you probably have good access to all of the branches. Just find the two vents which smell and work back from there.

You or an HVAC contractor should inspect to see if there are any holes in the ductwork, or even need to disassemble some of the ducts to see if there is something lodged inside (I hope not a dead animal like a rat.) Best case, you have some water dripping on the vent and stinking up the air.

Answer 2

Are the vents in a kids room? Vents in the Floor? What room are they in? If bath, laundry, kitchen you may have another problem. First look to see if anything has gotten into the vent. I would check to make sure all your ducts are sealed up tight. I would also check insulation on them. Are the ducts running under the house? When the High speed fan kick on it has more than enough force to send it down the duct, but if there is a leak it can pull in outside air. I wish you well in your repair.

Answer 3

Under your coils, there is a pan to collect condensation off the coils and drain it away to either the outside of the house (most common) or to the sewer. This pan and the drain line will grow algae and mold and need to be cleaned occasionally. If it's not too clogged up (and yours probably isn't because you would have water leaking out by the a/c) you can try the following: try to spray a mix of bleach and water into the coils and drain, you want it to drip into the drain pan and kill the algae and mold in the drain pan. Then use a wet vacuum on the drain line outside the house to suck and muck out of the drain so it will flow easily. You may need to repeat this treatment a couple of times to get the algae killed.

Answer 4

THe vents with the odor most likely have a common plentum.
In that particular line, there must be a low place that water is collecting due to condensation.
Find that low spot & jack it up & shim it to prevent a low spot.
Clean the line of the mold & build-up.

Answer 5

sounds like mildew. possibly not enough air moving through the vents normally, so mildew grows. when the system is on high, then the air is forced through those vents bringing the smell. larger ducts feeding those vents or restricting flow from other vents may prevent this problem. you'll have to get rid of the mildew first.

Answer 6

has to be something in the common ductwork for the two vents. trace it back to the comon duct and go from there.