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Old 02-28-2013, 05:19 PM   #136
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Will the size of my ducts have to be changed?


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Gotta be careful with window tint. My wife spent a fortune in tinting our front west facing windows, only to find the glass got much hotter.
I peeled the tint and went back in with new solar screens.

Maybe there are other types of tint that would be a better choice but for us, we tried two different kinds and they both doubled window temps.

I think you are right, I believe there is tint rated for double pain glass, etc.....

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Old 02-28-2013, 05:30 PM   #137
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Will the size of my ducts have to be changed?


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Window Tint!
thats a good idea DP. Once all the ac/heating is installed I will be doing a lot progressive things to take care of as many leaks as possible, kick up the R vlaues where I can.
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Old 02-28-2013, 05:49 PM   #138
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Will the size of my ducts have to be changed?


I used the duct sizing system and this is what I got for the "supply" for upstairs. I entered 1000 cfm and for "speed of air" it defaults to 900 with the word "recommended" beside it which is what BT said (875). The current trunk line is 8" for heating so the 7" round for supply would be great because of a couple of tight spots.
For "return" ducts it says the same thing as "supply" ducts the only difference is they reduce the speed of air to 700 with the word "recommended" next to it. Is that sound right? Then are the "return" "ducts" calculated at 75% the speed of air of the supply ducts?
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Old 02-28-2013, 05:53 PM   #139
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Will the size of my ducts have to be changed?


Return ducts
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Old 02-28-2013, 07:02 PM   #140
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Will the size of my ducts have to be changed?


Returns are slower then supply to help keep noise down.

That program unfortunately does not include a way of entering the TEL of the duct. So 7" may be a bit small, if its a long run.
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Old 02-28-2013, 09:51 PM   #141
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Will the size of my ducts have to be changed?


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Returns are slower then supply to help keep noise down.

That program unfortunately does not include a way of entering the TEL of the duct. So 7" may be a bit small, if its a long run.
2nd flr run - I think to go back from a return register might be 10' across 2nd floor attic, down the wall 9' and 14' across 1st floor attic back to heater = 33 feet.

1st flr run - about 32' to farthest supply duct from heater so it could be closer with a return register.

Are these considered long runs?
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Old 03-01-2013, 04:22 AM   #142
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Will the size of my ducts have to be changed?


Thats the linear length. Each bend/elbow has an equivalent length that gets added.

The second floor return run you describe could be 102 foot of total equivalent length. The longest supply run would then get added up for it TEL and added in to the return run's TEL. This could be over 200 foot total. Meaning using the 900 FPM (recommended) will give you a high static pressure and reduce air flow.
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Old 03-01-2013, 05:26 PM   #143
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Will the size of my ducts have to be changed?


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Thats the linear length. Each bend/elbow has an equivalent length that gets added.

The second floor return run you describe could be 102 foot of total equivalent length. The longest supply run would then get added up for it TEL and added in to the return run's TEL. This could be over 200 foot total. Meaning using the 900 FPM (recommended) will give you a high static pressure and reduce air flow.
The current ducting run for heating from 1st floor closet plenum to 2nd flr has 2-8" 45 degree elbows,1-8" 90, 1-8" t-wye into 5"/6" branches,1-8" t-wye into 6" branch to ceiling register of south bedroom,1- 8" to 6" reducer,1-6" 90 into ceiling register of north bedroom , 8" round transitioning to 9' of 14" x 3" rectangular duct with 5' of that 14" x 3" vertical duct behind the wall of closet in picture and 4' of that 14" x 3" goes over ceiling of that closet transitioning into 8" round running across 2nd floor attic.

Am I able to figure out the runs for my house and have it verified or is too hard?
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Old 03-01-2013, 05:42 PM   #144
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Will the size of my ducts have to be changed?


All the duct is round on this run except for the 14" x 3" vertical that runs up behind the closet wall and closet ceiling.
It seems to me that if the calculations show that 7" round or 8" round is what the trunk lines for supply/return need to be then I would think if I ran 7 or 8" round in place of that 14" x 3" vertical and just build the closet wall out some more. Round duct would have a lot less joints than that piece in the other picture. And isn't that the object for the inside of the ducts. Less drag on the air in the ducts?
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Old 03-01-2013, 05:49 PM   #145
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Will the size of my ducts have to be changed?


I was talking to my mailman today. He told me his ac unit runs all day long set at 78 without shutting off and he can't get the temperature in his house to come down to 78. He said even in the evenings he has trouble getting it to come down to 78. He did not know the tonnage.
I am sure there are many other things he might be able to do to improve his house but I could not help thinking a load calc would have helped. I am also thinking his unit is too small.
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Old 03-01-2013, 06:46 PM   #146
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Will the size of my ducts have to be changed?


An 8" isn't going to be a large enough trunk line for your second floor. With all the turns and branches, its gonna be too restrictive. A 9" round, or 10X7 would work better.

Under sized duct work is why many houses don't cool right. And people think they need a bigger system.
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Old 03-02-2013, 09:12 PM   #147
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Will the size of my ducts have to be changed?


I am thinking about putting another 22.5" x 5" soffit vent next to the existing vent. The only place I can run the new return duct is in front of that existing vent so there will be some blockage of air flow as the rectangular duct heads up to the 2nd floor attic. But if I put a vent to the left of it where the original heating duct ran the two vents combined should be fine for proper air flow. Right behind where you see the string hanging will be the new supply duct and the far right under existing vent will be return. Anyone see a problem?
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Old 03-02-2013, 10:07 PM   #148
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Will the size of my ducts have to be changed?


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The current ducting run for heating from 1st floor closet plenum to 2nd flr has 2-8" 45 degree elbows,1-8" 90, 1-8" t-wye into 5"/6" branches,1-8" t-wye into 6" branch to ceiling register of south bedroom,1- 8" to 6" reducer,1-6" 90 into ceiling register of north bedroom , 8" round transitioning to 9' of 14" x 3" rectangular duct with 5' of that 14" x 3" vertical duct behind the wall of closet in picture and 4' of that 14" x 3" goes over ceiling of that closet transitioning into 8" round running across 2nd floor attic.

Am I able to figure out the runs for my house and have it verified or is too hard?
You know that white coating is probably asbestos, right?
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Old 03-03-2013, 12:25 AM   #149
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Will the size of my ducts have to be changed?


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You know that white coating is probably asbestos, right?
yes, all the popcorn ceilings and ducts in the homes in my area have it.
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Old 03-03-2013, 04:26 AM   #150
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Will the size of my ducts have to be changed?


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I am thinking about putting another 22.5" x 5" soffit vent next to the existing vent. The only place I can run the new return duct is in front of that existing vent so there will be some blockage of air flow as the rectangular duct heads up to the 2nd floor attic. But if I put a vent to the left of it where the original heating duct ran the two vents combined should be fine for proper air flow. Right behind where you see the string hanging will be the new supply duct and the far right under existing vent will be return. Anyone see a problem?
Can't see the existing vent in that pic.

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