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Old 07-19-2012, 10:37 AM   #1
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Cooling delivery problems in my home need help?

Okay I have a newer home (1996), that I bought last year. I have done a large scale renovation to the home downstairs (custom kitchen with some wall removal and hardwood floors throughout 3 bathrooms redone etc)

The home when bought had a new 5 ton 15 seer AC and furnace air handler Gas heat. The house is 2 storiers, 3200 sf. The house is kind of a tripple hip key west design with VERY high ceilings in all the rooms. The great room of the house has escalating 10 foot to 20 foot ceilings the rest of the downstairs is all 10ft. The upstairs is all 12 foot.

The way the house is designe I have excellent insulation and on top of that I did a radient barrer wrap with new Hardiboard siding on the home as well. My major issue is that the AC duct runs have to run so high and so many bends to the upstairs there is always a 10-15 degree difference in temp.

You can actually tell it can not blow enough air out of the upstairs vents. The upstairs is a 380SF Master and a 300 SF open loft sittting area over the stairs. Both the loft and the master have returns 18" or 24" if I was to guess at size.

I was looking at zoning the system but after talking to some people zoning is great but If I dont have the proper air flow up stairs Its not going to work out right. The ducts inside are perft condition 8" and in some place 10" flex off the box. Box is set up correct for returns and outs nothing coming out of the end of the box etc.

The only access I have to the upstairs is a VERY small scuttle but the returns are using flex duct to go back to the main return in the attaic over the garage and flex duct delivery from the mains ducts in the garage.

I would say that it would be better if I had a duct box in the upstairs for return and delivery it would be better but due to the low pitch on the upstairs hip roof it can be done. the runs from the main duct in the attic of the garage to the upstairs have at least 3 90 degree bends and run over 25 feet.

I was looking for some way to use a Booster fan that was thermostatically controlled instead of a Zone system. But not even sure if there is such a thing. Zoning wont solve my problem it simply not enough air flow becuase of the large amounts of runs. There is also no room to add a smaller system outside for just the upstairs.

Any ideas are suggestions would be helpfull, I have had 2 AC guys come by and look and both want to zone, but they are complete idiots in my book if they can't see that even with a zone system I still can not get the right amount of air upstairs. I have closed off all the vents downstairs to and ran the AC and you can barely feel a breeze come out of the vents. I have told them this as well. since a zone would in effect do the same thing (yes at a better scale because of its location, but I can not see anyway it can do enough.)

Thanks for suggestions or any idea or help.



DaveFL is offline   Reply With Quote
Old 07-19-2012, 11:30 AM   #2
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Sounds like a duct overhaul that includes zoning is in order. Zoning CAN be made to work, but the ductwork must be designed to manage a zoned system and to provide effective air flow to all zones as needed. You mention flex duct quite a bit - in most cases, that's not a good thing, since it often means the installing contractor cut a lot of corners. Flex is _okay_ if it's installed correctly, but it's really intended to be used to terminate metal duct works at the grills. In fact, in most cases you really shouldn't have a flex run over about 8' long (that can vary, depending on the exact code adopted by the various areas).

Understand too that if you currently cannot cool the home without zoning, then simply adding a zone to your ductwork won't make much of a difference.


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Old 07-20-2012, 08:22 AM   #3
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The flex duct is part of the problem I will agree, as it is used to run to the upstairs Large Diameter Flex in this instance.

I am still partial to zoning with out increased air flow. That is one the the largest problems I face.

As for flex, There is no 8' run rull to apply to flex duct. Actually flex duct is one of the best ways to run off the main duct to any area's needed vs traditional metal. Of course if possible a Duct board is alwas best to run as far as nessacary but FLex duct if properly installed can run a large length with no comprimise. I have this actually from A Professor of building design Speciallizing in HVAC and proper installation for maximum effecency, I got this contact from a good friend of mine who is with Beazer Homes, even though they may have had the worts stock drop they are still the nations #1 green and enrgy star rated builders.

If he wasnt in NC he would have one of thier contracters look at it for me, but in my small town there just any contractor that "really" understands HVAC cooling potential and too many like to throw idea out there that sound good but when you look it up and read on "thier Idea" you find all kinds of flaws in what they are saying.
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