He's guessing at the size duct required and if your equipment is large enough to handle the edition.
Follow Advanced's advice.
Eliminating one elbow from the branch run is not likely to increase the air flow very much.
A top takeoff(round pipe ,not a low loss fitting) that turns the air perpendicular to the trunk ,adds more resistance to air flow then one elbow does.So if I have it pictured in my mind correctly,it might be worse if you change it.
Thank you, Dash.
I'll follow your and Advanced's advice and try to approach this correctly. Like I said, I think everyone is willing to cooperate and make it work.
are the ells set for 90deg or 45deg? having 2 ells close together set at other than 90 has much less flow restriction
harvest rainwater,make SHADE,R75/50/30= roof/wall/floor, use HVAC mastic,caulk all wall seams!
Thanks. They're both 90 degree elbows. I don't know if my previous description was confusing, but the new duct is an elbow that comes out the right side of the trunk line, curves up, joins another elbow which curves left and joins a duct over the trunk line. So, in other words, the new duct forms a U-Shape as soon as it comes out of trunk.
Just one more question about this.
The area we're trying to heat and cool is a new finished basement and we're getting very little air from the 3 new ducts that were added to the downstairs supply. We're going to try to remove some elbows but that may not help much.
The basement is very well insulated and doesn't need much heating or cooling, but more than it's getting now. The upstairs zone seems to have much more capacity due to fewer rooms and existing ducts - there is also much more air coming out of the upstairs registers - more than we need.
Is it a really bad idea to run the ducts for the basement off the supply for the upstairs zone?
If the basement can do without the air flow,it's okay ,I'd think,hard to tell from here.
If it's all one system "partially" closing dampers in duct or at registers on the first floor will direct more air to the basement.Don't close them very much as it increases the static in the system and reduces ocerall airflow at some point.A competent contractor could measure the static while adjusting the dampers to be sure you are still getting the required air flow.
There are better(less restrictive) fitting to use for comig out the top of the trunk than a 6" elbow.
It would be 10 or12" X 6" rectangular ,tap into the trunk,tapering to the 6" round and you add a elbow for the turn.7"or 8" round duct would likely be better as well.
My advice DIY would be to click the bullseye and do a load calc for yourself. Even if you don't understand what the numbers mean you can at least show your report to someone who does and they can make the proper assessment for you.
Thanks. I'm not sure I understand your reply. The downstairs zone is working just about right and I don't think we can damper any of the ducts for the first floor. In fact, there's one room far from the furnace that's pretty weak and could use more airflow.
The second floor, on the other hand, has more than enough air coming out of the registers and I would guess that diverting some to the basement would not affect the performance much. Several of the ducts going to the second floor have even been dampered to reduce excessive air. The two zones share a common return, so the returns would not need to be changed.
I actually did purchase HVAC Calc about 2 years ago and did a load calc and the load for the 2nd floor is much less than for the first. (Thanks, seton.)
So... if I'm correct about having more static pressure available in the 2nd Floor system, should it be OK to provide heat for the basement from the 2nd Floor system? My thinking is that the only difference (which system supplies the heat/AC) is which floor requires more or less heat/AC compared to what the basement will need. It seems that the less heat the 2nd floor usually needs will be sufficient for the basement and the more AC the 2nd Floor needs in the summer will probably not be excessive for the basement and might even work out better because of the many lights and other heat generating devices in the basement.
I appreciate your time in helping. Like I said, I wish I had you guys doing the work. When I ask these questions here, I usually get weird looks but no answers.