Trying to finish a basement, and where we intend to put a partition wall with a door is right where a contractor left a 6" duct below the floor joists. He did this to go under a piece of microlam that is used of support in that part of the house.
I know better than to cut into the microlam, but can I purchase a some ductwork that will flatten out in the area where it will pass under the microlam and hug the ceiling ? If I could recover 2" I could install a standard interior door without modifications.
6" duct is equivelant to 3 1/4" X 10" rectangle, so figure it will hang down about 3 1/4". They sell 6" round to rect converter pieces at Lowes or HD. You can get straight or a 90 deg converter if that helps you.
There may be such an animal, but I've never seen one. You might have to cut the round 6" and move the elbows farther away from the beam, then reinstall the elbows, and add the transition pieces with the rectangular duct in between the elbows.
Oval ducting is being used in new construction in our area and there is some stock in local box stores like Menards IIRC. There were adapters and transition pieces, some of which could work for you. They are sized to go between partition studs. An alternative would be asking a good sheet metal shop to price a duct to duct adapter. The modest price may well be worth not having the aggravation of cobbling together a run of oddball non stock fixtures. Good luck.
Go to HD or Lowes and go to the sheet metal duct area, and put together some pieces and see if it will work for you. Bring a ruler so you know more or less where you would have to cut the existing 6" round. When you look for the 90 deg part that has to around the beam, look for a "short" 90 to give you max clearance. You might find it in the section where they sell the range fans, dryer connections and accessories.
I see several choices depending on what your actual situation is wrt routing.
The "best" would probably be to go back some distance on either side of the glulam and insert a round to rectangular transition, go to a 45, add sufficient length to reach the next 45 to horizontal transition, carry it under the 'lam then reverse the sections on the other side. This will give you the clearance at the low point with the side benefit of minimizing and reducing existing pressure drop in the existing 4-90's at the cost, of course, of making the transition on both sides longer.
Sorta' like (you'll need non-proportional font for this to have any chance at all)...
| | O O O -> -- | | -- -> O O O \\ |_| / \\-------/
where the "O" is the round and the "-\\/" are the rectangular sections and the arrows indicate the transitions. You could, of course, do the first to elbows in round and transition going down but am assuming you'll need that to be as tight as possible.
You may need the rectangular 45s made at a tin shop; the rounds should be readily available or could use the adjustables if not.
I will visit HD or Lowes tonight. Also, should I be concerned about adding these transitions and an extra elbow ? Will this add significant static pressure to this run ?
You have enough problems now with the four 90s in close proximity. dpb's suggestion of using 4 45s would help with the static pressure. I'd do the 45s in round duct and use the transitions just on the flat rectangular run.
Of course other factors we can't see might prevent you from choosing the extended, smoother transition solution.
... That would leave him still at the same bottom height once he made the return to horizontal is the problem. He needs to get to the lower profile earlier. He could do it in the transition, but I figured might as well just go ahead and make the transition, then the detour.
Reiterate what I said earlier and your agreement; this will be _less_ static pressure than previous using 4-90s. I don't see where OP gets the "extra elbow" idea...
*You can get just about any duct configuration fabricated at a sheet metal shop. Some A/C contractors have their own shops that fabricate or there are independent companies around. Check your yellow pages. The cost may not be too bad. You will need to at least provide them with measurements although a rough diagram with measurements would be better. Maybe you need to transition from round to rectangular.
That's not necessarily so. He'll be working it backwards from the rectangular duct which is placed up tight against the beam. The bottom of the rectangular duct will be the same as the bottom of the round-to-rectangular transition.
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of the height differential, connections and potential headroom savings, will take place above that.
This I do not know. Maybe it's a time and materials job. ;)
You need to maintain the same number of square inches. If the existing is 6" round, the square inch capacity is about 27 square inches. Stop at any tin shop, explain your problem, ask them to make a transition that will work.
If you are framing a wall directly under the glulam, add two lally columns that are swallowed by the wall and go through the glulam.
RicodJour, The pic that you posted is almost exactly what I need. I had imagined something like a transition offset to one side, but with an elbow pointed upward. I will try to get a pic of the problem posted. The extra elbow(s) that I was talking about was the extra elbows needed to run the duct back up in and through the floor joists. The contactor after elbowing the duct under the microlam just suspended the duct under the floor joists for the rest of the run. There is room to run the duct through the joists and recover some ceiling space in that area.
Uh, NO!. Leaving aside questions about possibly weakening the gluelam out past the top pads on the lally columns, you are assuming the floor under the base of the columns will handle the point loads. Sure, it will PROBABLY work for a few years, at least until OP moves, but you can never be sure. Any time you add a column to replace load-bearing structure, proper procedure is to add a footer under it. At a minimum, you need a plate to spread the load.
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