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BlueBSH 09-13-2010 11:03 AM

2nd floor low CFM
 
alright, the 2nd floor has a low CFM per vent, its effectively 1/3rd what it is on the 1st floor... it gets there by going from the main plenum duct that runs the length of the house then to a takeoff with a damper (fully open right now) then to a flex duct that runs about 15 ft, that turns into a 90 degree round to oval elbow then goes up the walls in an oval riser duct to a register box in the wall... the total length up is about 11 ft plus the elbow, and the 15 ft of flex to the supply plenum duct....

anything I can do to increase CFM to the 2nd floor? would a duct fan on the runs going up help?

kenmac 09-13-2010 09:24 PM

Quote:

Originally Posted by BlueBSH (Post 500341)
alright, the 2nd floor has a low CFM per vent, its effectively 1/3rd what it is on the 1st floor... it gets there by going from the main plenum duct that runs the length of the house then to a takeoff with a damper (fully open right now) then to a flex duct that runs about 15 ft, that turns into a 90 degree round to oval elbow then goes up the walls in an oval riser duct to a register box in the wall... the total length up is about 11 ft plus the elbow, and the 15 ft of flex to the supply plenum duct....

anything I can do to increase CFM to the 2nd floor? would a duct fan on the runs going up help?


Don't know how much air your trying to move.. Metal pipe will move more air than the same size flex. don't know how your system's set up.. You may be moving all the air the unit can move.. Has the air flow always been low for that area ?? You may also need an air deverter installed in the duct to devert some air into the other duct

beenthere 09-14-2010 05:33 AM

The run you describe is roughly 156' of total equivalent length. So its very resistive to air flow, compared to your first floor runs.

Run hard pipe from the trunk to the oval to round ells for the second floor. Install dampers on your first floor supplies, and reduce their air flow slightly.

May want to get scooped take offs for the second floor supplies.

BlueBSH 09-14-2010 09:18 AM

Quote:

Originally Posted by beenthere (Post 500846)
The run you describe is roughly 156' of total equivalent length. So its very resistive to air flow, compared to your first floor runs.

Run hard pipe from the trunk to the oval to round ells for the second floor. Install dampers on your first floor supplies, and reduce their air flow slightly.

May want to get scooped take offs for the second floor supplies.


I'l definatly look into the scooped takeoffs, didn't even know they existed, but seems like it might help redirect some air flow... I like the hard line idea too.

always 10 degrees hotter or cooler upstairs, just want it to be a little more level in temp with the 2nd floor :)

beenthere 09-14-2010 03:28 PM

What is your return set up on the second floor?

BlueBSH 09-14-2010 04:22 PM

Quote:

Originally Posted by beenthere (Post 501054)
What is your return set up on the second floor?


it's pretty crappy in my opinion, but hte builders thought it was fine... here's how the return from the 2nd goes to the furnace...

2nd floor rooms have a hole in the wall with a 6 x 14 grill on them, those go through a joist cavity into the sub floor then inside the subfloor they have to go through a perpendicular joist to get to a wall that is offset from the 2nd foor wall by 8 inches (effectively making the whole floor joist cavity that is perpendicular an empty void for the return plus the whole 8ft void in the 2nd floor wall, plus then the wierd hole they cut through the 2x10 joist to join it to the next joist cavity over then it finally goes down the 1st story wall 8ft to the basement where the cavity is thermopanned over then a 12x12 return trunk connects to that and then that finally goes into the main return trunk..... crazy static pressure on the return? probably......

beenthere 09-14-2010 04:30 PM

On that return run there sure is.

If there is anyway you can redo or improve it. that will make a world of difference.

BlueBSH 09-14-2010 04:32 PM

Quote:

Originally Posted by beenthere (Post 501086)
On that return run there sure is.

If there is anyway you can redo or improve it. that will make a world of difference.

that's the thing that scares me, redoing it... lot of work, lot of ripped up ceilings / walls ugh... builders

beenthere 09-14-2010 04:35 PM

Anyway to run the return through the attic over to that chaise.

BlueBSH 09-14-2010 04:38 PM

Quote:

Originally Posted by beenthere (Post 501092)
Anyway to run the return through the attic over to that chaise.

that might be an option I didn't think of... might have to get someone to help me look into that though, just to make sure I can run a line back down to the basement somewhere without somethign in the way

beenthere 09-14-2010 04:45 PM

If you can find a guy by the name of Will, then there is a way. :laughing:

BlueBSH 09-14-2010 04:48 PM

Quote:

Originally Posted by beenthere (Post 501099)
If you can find a guy by the name of Will, then there is a way. :laughing:

hehe I'll call my local hvac people and ask if they have a Will working for them :laughing:


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