Heating for finished attic

Discussion in 'HVAC' started by envoys, Jan 15, 2007.

  1. Jan 15, 2007 #1

    envoys

    envoys

    envoys

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    Hello,

    The house I purchased has a finished attic that is sort of like a loft area. The one side has access for storage and the other side has access for the heating. Now, the heating and cooling does not get up to this level very well so I decided to investigate. The installation of the piping is 5" steel running from the furnace to the top of the attic, both cold air return and heat/cooling. Ok, now upstairs, when the furnace is on or the AC, there is very little, and i mean very little air coming out of the vents. I crawled in behind where they ran the pipe and found out that they have used some weird pipe I have never seen before, it is 5" insulated pipe, but inside the insulation looks something like a hose you would use on your dryer. The steel pipe comes up from the basement, and is T'd off for 2 vents. The T is very warm when the furnace is on, so I know the heat is up there, not could it be this "insulated" pipe causing me the grief and should I switch it to steel or have someone come in and look at the furnace?

    Thanks. I hope I was clear enough.
     
  2. Jan 15, 2007 #2

    glennjanie

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    Welcome to the Forum Envoys:
    What you have discovered is called Flex-Duct. When it first came out it was stated to be limited to 3' runs, anything more just wears the air out trying to jump over the wires. Yes, you do need to change it out for steel pipe with sleeve insulation on it. The smooth steel will allow the air to speed up to the attic and the insulation sleeve will prevent loss of heat. Let us know how it turns out.
    Glenn
     
  3. Jan 16, 2007 #3

    envoys

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    Thanks for the info! Designed for 3' runs huh? No wonder why its not getting any heat up there, there is 1 run of 30'! I will be changing this out this weekend and will let you all know how it goes. Thanks.
     
  4. Jan 16, 2007 #4

    glennjanie

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    Hey Envoys:
    Just for a "before and after" test; hold a candle near a register with the flex pipe on it then, after the steel pipe is in, hold a candle in the same place. You will be thrilled with the difference!
    Glenn
     
  5. Jan 16, 2007 #5

    envoys

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    Ok, I will definately do that, maybe I'll do a short video of it for proof...that's if the candle even moves in the wind with the flex pipe on hehe.
     
  6. Jan 17, 2007 #6

    Daryl

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    Possible too that there is to sharp of a bend in the are of change over that it's actually pinching off the air flow. You should have an air flow of 100 cfm at the register opening. I know, not every one has an air flow meter! 100 cfm is enough of a flow you can very easily detect it as movement over your hand. If there are several turns in the pipe between the furnace and the register this will severely cut down your air flow. (especially if they are 90deg. turns. THis causes a whirlwind effect at the turn which restricts the flow.
     
  7. Jan 20, 2007 #7

    hvachawk

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    the flex duct can be ran more then 3ft ,but the way they did it is not right .
    there must be a kink in it or it is torn in the wall some were.

    with out looking at it its hard to tell you what to do ,so if you can post some pictures it will help.

    charlie
     
  8. Jan 22, 2007 #8

    envoys

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    Ok well I replaced all the flex duct with galv steel pipe, the air flow is still rather low but it is better then before...i will try and explain how the pipe gets up to the attic, it might not be the proper way they did it but you tell me... off the furnace comes a pipe that going to the register in the bathroom, that pipe has a T in it and then off the T is the pipe that goes upstairs...and obviously to go up, there is 1, 90deg on it, when it gets the the attic, there is another T that splits to 2 registers. That's all I can think of for now, maybe you guys can shed some light on this situation why it is so low...the register in the bathroom shoot the heat out like a hair dryer, same with the other registers in the house.
     
  9. Jan 22, 2007 #9

    Quattro

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    Have you tried closing your bathroom register 1/2 way or more to see if that increases flow to the attic? It's a quick and dirty test, but won't solve the problem...and your bathroom will be cooler!
     
  10. Jan 22, 2007 #10

    envoys

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    I've tried before and it didn't seem to do much, I'll try again with this new piping when I get home from work.
     
  11. Jan 23, 2007 #11

    envoys

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    here are some pics of the setup off the furnace... I have only labelled the pipes that go to the attic and to the bathroom... have a look.

    IMG_0140.jpg

    IMG_0141.jpg

    IMG_0142.jpg
     
  12. Jan 23, 2007 #12

    Quattro

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    Someone help me here, but can't you put in a "diverter" at that T-joint to move more air down the attic run? Something like a flue damper...

    I think the forced air is taking the path of least resistance and mostly blowing right past that T-junction, and ending up in the bathroom. You need a way to 'steer' some of it down that pipe.

    OR- remove the T-junction and replace with a Y, if it'll fit between the joists.
     
  13. Jan 23, 2007 #13

    glennjanie

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    Nice pictures, Envoys:
    Yes, a damper can be put in the line just on the bathroom side of the Tee. The damper is a round piece of sheet metal with pivot pens on both sides of it; a handle is attached to one of the pins and a locking nut holds it in the position you choose.
    Both the supply and return air pipes need sleeve insulation on them; it would give you about 1/3 more heat in the attic.
    Another alternative would be to put a reducer fitting in the bath side of the Tee and run a 4" pipe from there on; that would force more air to the attic.
    Glenn
     
  14. Jan 23, 2007 #14

    Hube

    Hube

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    Envoys; first off, adding a tee ot a run is an absolute no-no. adding a Y would still be a bad thing but it may streamline the air a tad better. i hope I don't upset the cart but from the pics i see you have a rookie diy installation,.in other words whoever butchered this mess should have shot and p....d on.
    In order to get some supply air up into this attic (loft you should have a seperate run, perhaps 6" diam terminating to a 4x10 or4x12 register. Get rid of that tee and keep the bathroom on a single run with a damper in it so you can "throttle the air down somewhat to the bathroom. Cut in a new 6" diam run off the plenum with a damper and run it up into your attic /loft.
    A lot will depend on your furnace's rated CFM and btu output ....you may have to increase your rpm slightly and or 'balance all the other existing supply runs in order to throw more air the attic way. And you will absolutely also need some RETURN air from this attic/loft, in order to get some decent supply air up to it.
     
  15. Jan 23, 2007 #15

    envoys

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    I will investigate getting the damper installed...in the attic, i installed sleeve insulation over all the pipes. It is much warmer up there, but not nearly as warm as it should be, tonight I will take a temperature reading. Right now I have some other issue with my furnace blowing cold air until I shut off the main power to the furnace for 15mins and then back on, then it blows hot air and works just fine for about a week.
     

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