can a leaky supply takeoff collar draw in dust?
I have been experiencing a dust problem in the house, including fiberglass particles. I noticed while doing some investigating and sealing for air leaks around the furnace that a small unsealed crack at the juncture of the supply plenum and supply trunk line was actually drawing in smoke from a incense stick. I would have expected this crack to have been blowing out air.
Would it be possible or does anyone know whether this may be common at the duct takeoffs where the collar is attached to trunk line. These are covered with foil faced insulation and taped with silver tape. However I dont think the collar to duct joints may be sealed on all these. Any comments opinions or experience with this appreciated.
Usually leaks in the supply side will blow air out, but it is also possible for air to be drawn in due to the venturi effect. It just depends on the dynamics of the airflow in that particular area.
Supply air leaks, that actually blow air out, are really bad for more than one reason.
The most obvious one is that the air that is leaking is air you just paid to heat or cool, it is the most expensive air in the house.
Less obvious, but very common, and IMO is the worst thing about supply leaks, is that they depressurize the house. All the conditioned air that leaks to outside the conditioned space gets replaced by unconditioned air from outside the conditioned space.
Some of it will come from around doors and windows, which is at least relatively clean fresh air.
Very often most of the replacement air comes from dirty buffer zones, like from the attic, wall cavities, crawl space, etc., which is bad...
You would be surprized how much air small hole in the duct work can draw into the air stream as well as come out of the air stream !!! Look on the return side of your duct work and look for areas around where the connections are made or any small holes you will see a patch a dust around any holes or gaps in the duct work. Also you can eliminate a good portion of the dust in your house by running your fan on low 24/7 will help because you will not have the fan sarting and stopping frequently which kicks up dust in the duct runs everytime the fan starts up thru vibration on start up, so when you have the fan running on low speed all the time you in effect eliminate most of that. And the best thing you can do is to seal all the duct work from the furnace to the end of every run in the home and of course insulate. Mastic #9 which you can buy at most home centers works really good and is very easy to apply. A good filter also helps
thanks for input
thanks guys, looks like i got to do more sealing. System I replaced had a bottleneck in return duct and was drawing in lots of dust thru every penetration in plenum and furnace on return side past there. big dust trails and duct mounted humidistat was clogged with dust. Found chase from basement to garage attic and then on up to house attic was not sealed and this in effect created a super highway for dust (fiberglass) from these areas. I sealed these bypasses and I think that any reisidual dust is now being blown out thru walls by leaks in duct inside the chase. May try a aeroseal contractor or even try foaming around ductwork in the chases to seal leaks in this enclosed space. appreciate the feedback.
If his dust problem is due to duct leakage, running the fan constantly would make the dust problem worse!
Originally Posted by DanW13
It would also increase energy usage, and during the cooling season, increase indoor humidity.