Duct Work Question

I have a situation concerning the heating/cooling ducts in my home that I have a question or two about.
I have a moldy smell eminating from a register. Upon inspection of the duct work leading to this register, I find that this register's duct branches off of the main duct from the furnace. The main duct is rectangular in cross-section. The branch that gives off the moldy smell is round (6 inch I think).
An examination of the joint between the round duct and the main rectangular duct reveals that whoever did the work of making the original connection had to have been a complete amatuer. The round duct isn't even connected, or the connection has failed. The round duct appears to be merely inserted into a hole cut in the top of the rectangular main duct......no tape, sealer, screws, or any visible means of connection!!!!
I am going to fix this, but there is very little clearance to work in above the rectangular main duct. I intend to cut a new outlet on the side of the main duct, fit the proper fittings ( two 90 degree bends shaped into an _|`` form, which should redirect the airflow to the approximate position I need to reconnect the round duct), seal up the old outlet hole, demold the duct, and hook it all back together.
1) How do I best seal up the old outlet hole? I appears to be about a 7 inch diameter round hole on the top of the rectangular duct. I am thinking sheet metal, metal screws, and duct sealant caulking or a gasket will do the trick. Does anybody make a part specifically for sealing up old outlet holes as I have described? If so, who, and how do I get one? There is very little working room in there, so if a part is available that can easily be slipped in and secured, it would really hep.
2 About the mold.....I have been told clorine bleach will be best for washing out the old ducts (they are galvanised metal....so the mold will NOT be embedded) before I reinstall them. Is this correct, or is there some other type of product that I should use?
Thanks for any help. Dave
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Dav1936531 wrote:

inch
sheet
You are on the right track. You want to use a special duct mastic to seal the patch.
http://energyoutlet.com/res/ducts/materials.html
http://www.energystar.gov/ia/new_homes/features/DuctSealing1-17-01.pdf
...

--
Joseph E. Meehan

26 + 6 = 1 It's Irish Math
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snipped-for-privacy@aol.com (Dav1936531) wrote:
-snip-

I wouldn't bother trying to clean it. Buy new- insulated- duct.
I don't remember the price, but I'm a notorious 'cheap bastard' & 10 years ago when I went to buy a short section for a repair, it was so cheap I bought enough to replace all the basement ductwork.
Jim
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<< I intend to cut a new outlet on the side of the main duct, fit the proper fittings ( two 90 degree bends shaped into an _|`` form, which should redirect the airflow >>
You should reconsider this plan. Any 90 degree bend in ducting rduces airflow considerably. There are charts trhat describe these losses that some our NG HVAC experts can comment on better than I can. A pair of 45 dgree fittings may accomplish what you need with more effficiency. Talk to a sheet metal shop tech about a 45 dgree outlet on a new section of ducting. Price ought to be nominal and could make the job easier. Good luck.
Joe
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