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Thread: Insulate duct's

  1. #1
    Join Date
    Nov 2005
    Posts
    65

    Wink

    Hi, I have a new ducts instaled and Carrier Infinity MVP 56 furnace and Performance condenser 3 ton.
    I have heating going very lucluster to front of house LRm ,Drm, Kitchen.
    Duct[38feet 16x8" is run with 4- 90 degree elbow from furnace room to crawl space which semi insulated [walls are brick ,cieling drywall and insulation between joist],
    duct main trunk runs surface on that cieling then supply branches round pipes 6",6 registers trough floor ,air flow pressure not enough,room is cold 5-7 F degreee diference where t.stat located.[infinity controll]
    also when heating, i touched the duct in crawl space is nice warm , shuld be inuslated? and how, with what material, thnaks Gy

  2. #2
    I am not an expert, just another homeowner,...

    You may have several factors contributing to your less than satisfactory heating. Inadequate insulation or lack of it in the crawl space might be one of them. Supply lines definitely need to be wrapped, but if the crawl space gets much colder than the living areas, I'd consider to have the return insulated as well.

    If the furnace is at one end of the house and you have weak air-flow at the other end, your furnace blower might not have been set properly to provide enough CFM.

    Clogged/dirty filter may be yet another culprit.

    If the work was done by a professional installer/contractor, call them back to address your concerns before it gets really cold.

    Good luck!

  3. #3
    Join Date
    Nov 2005
    Posts
    65

    Ducts

    Thanks bdawg
    ,this is the deal:
    its a brand new install [yes i caled the instaler back ,just take time for him to show up]furnace a/c and ducts.
    The furnace is about in middle of house single story,
    this trunk is making 4 -90 dgr elbow in furnace room, then
    in crawl space is straight run and reduced twice as the supplies going out from it, yes is uncondition space
    the return does not going there ,is actually above it and trough wall to the beggining of space above Lr,DR Ktchen.
    Then another trunk line goes oposite dirrection -conditioned space [serves 2 bedrooms, and family rm in basement also 6 suplies reg form it ,over here is verry hot .
    How do you insulate ? thans GY

  4. #4
    Join Date
    Feb 2003
    Location
    Huntsville,AL
    Posts
    4,125
    insulate crawl walls, seal off any vents, cover earth with 6mil pvc!
    read at BUILDINGSCIENCE.com
    harvest rainwater,make SHADE,R75/50/30= roof/wall/floor, use HVAC mastic,caulk all wall seams!

  5. #5
    As cem-bsee has said, sealing off the crawl space is a good idea; however, whether you do it or not, you should insulate the supply ducts.

    Your contractor should've done this already, but you can go to The Home Despot or Lowes, or any HVAC supply store and ask for duct insulation. It's not a big deal, just wrap it around the ducts and either staple the edges together or use aluminum tape to secure it.

    Is it only a difference in temperature between the two ends of the house, or is there a noticeable difference in air-flow? If it's only temperature, then it's likely due to heat dissipation in the unconditioned areas. Weak air-flow would indicate either incorrectly sized duct(s) or obstruction in it.

  6. #6
    Join Date
    Nov 2005
    Location
    chicago
    Posts
    8

    Confused Ducts

    Yes the airflow is verry weak in front versas the rear rooms, the instaler coming out thursday, wil se what he have to say, i called them yesterday and they say will have you on sched. 1st or 2nd week of Dec. I say No Way ,you better come out right away ,il be calling the credit card company for reverse charges imidiaetly if this probelm is not solved by Thanksgiving holliday ,
    so they caled me today that they coming thursday ...
    Well remain to be seen, right?

  7. #7
    Join Date
    Sep 2001
    Location
    Vancouver Canada
    Posts
    996
    Insulate crawlspace, then add a couple of runs into it. Presto conditioned space. Also if crawlspace is heated it will warm the floors above making them more comfortable. As far as the airflow problem, any system with 4 elbows inline on one end and none on the other end is not going to be balanced, they will have to install balancing dampers in each main supply duct and adjust them for correct airflow.
    "Go big or Go Home"

  8. #8
    Join Date
    Nov 2005
    Location
    chicago
    Posts
    8

    Ducts

    Hi: The crawlspace is insualted cieling and covered w/ drywall i did that 25 yrs ago myself, floor is ground covered w/ tar paper ,used as storage lots of cardboard on shelf floor the height is ideal 48-50 inches ,
    now how do you make the trunk line elbows to end of run ?
    all 4 90 are in frunace room, 2- flat on cieling as coems out from plenum ,and 2 -6 feet away when the crawl space acces is lower so 1-90 internal and 30" drop then 1-90trough the brick wall, 16x8" trunk then few feet inside crawlspace on cieling first supply pipe6" round for kitch register , after this reduced to 14x8" to next reg reduced to 12x8" next reg, and reduced to 10x8" for 2 last registeres total of 6.
    The whole length of trunk is 45 feet from plenum .
    Also hte return is 16x8" but is right abve where the trunk goes trough furnace room to crawls space [bricjk wall],but the gril is in vertical plaster wall to the living room ,the faar end is 27 feet away 23 wide the whole room which is liv.rm din. kitchen ,some closet ,main entrance door large windows 1-14 feet x6feet high and 1-16ft x6feet high aluminum double pane glass 23 yr old. cieling is 9 ft high ,floor is subfloor type plus hard wood on top.
    It was always cold this rooms before i had water -radiant-in cieling system, always cold in cold days 30F ,never got over 64-65F ,today we have here Chicago cold and is 63-64F there i left the old dig thermostat there and this is waht is reads.
    Bedrooms are 70F, tstat new one infinity is around corner just of the start of LR. there is 72F.

  9. #9
    Join Date
    Sep 2001
    Location
    Vancouver Canada
    Posts
    996
    Sounds like the ductwork is ok for size, could be a little bigger before it enters crawlspace to compensate for the restriction in the elbows. How warm is it in the crawlspace? If it is fairly cold, insulation on ductwork will help to stop heat loss. May main cocern would be to get more airflow to that end of the house. Have to put a damper in the other end to adjust the airflow also check fan speed on heating and see if you can boost it higher.
    "Go big or Go Home"

  10. #10
    Join Date
    Nov 2005
    Posts
    65

    Ducts

    Hi:
    Have to mention one thing: One moore trunk line originates for mplenum 16x8" for the rear end of house serving 2 bd rm 1 bath,and family rm in basement finished total lenght is only 22feet w/1 elbow and reduced once to 14x8" ,have total 6 reg. coming out of it ,heat is great or too great i may add especialy in basement family room.
    Then from plenum going out 2 6" round pipes :1-to 6 feet lenght abve small bedroom [my eldelry father loves it good hot there],and 1- 6" pipe going to bathroom reg and T in midle of run 18feet register by the stairs to basmenet its real good keep out cold from side entrance doorway.
    I read online about Johns MAnvile duct insulation
    Microlite 75'x4'x2 i think thats i need in crawl space ,right?

  11. #11
    Join Date
    Nov 2005
    Location
    Colorado Springs
    Posts
    1
    so I am planning on insulating the ducts in my (uninsulated) crawler, sounds similar. here is what i have planned, take it for what its worth.

    1) Seal up all vents to the outside
    2) Seal up EVERYTHING from water penetration (Walls and Floor) since floor is dirt, thats where water will drain
    3) insulate all the walls with rigid foam
    4) drop a couple of downheats conditioning that space with one open vent to the rest of the house. now i will not have to worry about my water pipes freezing when the outside temp dips down.

    so positive pressure in the crawler forces water down, and converts crawler to conditioned space warming the floor above it (below my living room)

    when insulatin ducts, anyone every bring up freezing pipes? another unwanted expense that might be avoided.

  12. #12
    Join Date
    Nov 2005
    Posts
    65

    Carrier Infinity High heat off

    I set in Infinty control the thermostat setting in comfort, but the heat stage i selected Low, since lots of times the furnace reved up to high heat when the setting comes up like in morning and afternoon, altough the setback is no moore then 2 degrees, so i didnt wanted to burn gas for this buildup.
    Am i harming the furnace by this ? This furnace have 2 heat exchanger what is called? If the furnace i working on low stage ,then the 2nd heat exchanger is never used right? or please explain. thnaks Gy

  13. #13
    Join Date
    Nov 2005
    Posts
    65

    Carrier Infirnity control newer version

    I got to have replace my Infinity control from 2005 with same but i find 2 new items on it-in it rather.
    1: Switch SW3-4 : off [change at furnace] ,i odnt know what this is for in Furnace setup .
    2: G-Terminal : Disabled , if enable got fan speed: low,medium, high auto
    also in furnace setup area.
    the installer dont know,what these are and he lost the new manual guide,will get me a new one said,
    but i would like to know , when enable it nothing changes.
    Thansk Gy

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