The 8x20 does reduce after 4 (3 of which we are talking about) take-offs in 15' after it goes through a wide/long side 90 and imediatly into a 12" round. The 12" round has 1 take-off of it then reduces to a 10" round after 8'. The 10" round runs the length of the house (25') under its girders (tight!). The 10" round ultimately has 4 equally spaced take-offs and is capped. All metal branches have dampers and are masticed and insulated with a vapor barrier, then masticed again over the FSK tape. We have been through 9 gallons of mastic so far.
Everything is done working from the farthest point back toward the air handler which is what I am discussing here. Its been two solid weeks for two techs. The job is impecable and the techs have been great at putting up with abuse. Did I say this job is tight...everyone has worn out the toes in a pair of shoes, pants pocket and jacket elbows. Not to mention the square lumps to the head on the hour. I truly am happy with this job so far. But we are at a point where some experience needs to come into play to do it justice, and they are a little short on that it seems.
Gotta run will return shortly.
Any competant sheet metal worker could make a fitting set both ways in one fitting 24" is plenty long enough make it ogee and there will be little or no restiction probably a 50 spot to make and save alot of framing rework.
Originally Posted by brian in mass
Yes, certainly under is under.
The AH cannot be moved so any lateral off-set of the trunk away from the girder, would have to be corrected back. While a small lateral off-set could be done, you will still need a immediate 90 out of the trunk to go down and a 90 to go under the girder...if I am fallowing you.
There is currently only 2-2.5 inches of the trunks 8" side below the girder.
Dog...Fitting in the trunk? ogee?
I will try a search so as to not feel inferior.
Originally Posted by Dog
Ok...ogee is shaped like an "S", sort-of. Where would this referenced fitting go?
I was at first thinking you may be refering to an "upside down Y" which would be located under the AH. Basically instead of using the 8x20 below the AH. The techs had mentioned using a plenum divider/baffle proportionately located according to supply demands of the system to one side or the other.
Is there a particular methodology that seems most sensible for this situation by anyone fallowing along?
(drop down, go 3', then back up)
imo from all that has been discussed this would have been more to your avantage. As long as the drop and raise are ar least 18 inches in lenth and the piece of duct inbetween was 3 to 4 ft long. Yes you would have some turbulants but as long as the first takeoff is about 12in from the end of the drop you would most likely be fine. From what you have discribed if i am reading you right the girder is the biggest problem. Since the installers have reduced the duct as it goes along you should imo be able to use a drop and raise sucsessfuly. This is providing the fitting are made correctly
Thanks tinknocker, and to all who have added to this discussion.
The techs seem to be keen on the "sleigh", simply for a clean and less intrusive install. They admittedly are unsure of any ramifications the sleigh may pose to air-flow. They commented that it might be best to actually use a 8x8 or even 8x10 square duct in the center of the sleigh (37" drive to drive-if used) to create a branch trunk for all 3 supply branches needed. Run that branch trunk up tight to the bottom of the floor joist, go near 8' into a 8x8 90 for another 10' and cap. One 6" take-off (8' long) would be in the middle of the initial 8' length. The other two 6" take-offs would be within the last 3-4' of the 10' section. Dampers would be installed into the three 6" TO's.
I have a few days of down time as the techs needed to attend other business. I believe they will become members here. I will try to post pics shortly.