Duct work

Discussion in 'HVAC' started by Just, Jan 15, 2018.

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  1. Jan 15, 2018 #1

    Just

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    Hi all. For some reason I ran a 6 in duct off my trunk line to my up stairs bath room. I only need 35 cfms not the hole 100. Instead of tearing out that duct run can i just add a damper after my take off?
     
  2. Jan 15, 2018 #2

    Snoonyb

    Snoonyb

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    Absolutely.
     
  3. Jan 15, 2018 #3

    Just

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    Another quick question, to find how much cfm a room needs in taking LxWXH taki,g that number times the air change in an hour. And then dividing by 60 it that how to find the cfm per room ?
     
  4. Jan 15, 2018 #4

    bud16415

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    That sounds correct but you also have to think about the return air. The room is a closed box and blowing air into it needs a way to get out. Maybe under the door.

    Having the larger line going to the room is fine just dampen it on one end or the other to suit what your needs are.
     
  5. Jan 15, 2018 #5

    Just

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    Ya I had to put all new duct work in and new furnace and the guy that put funace in told me what duct work to get
    Just making sure I'm doing this right
     
  6. Jan 15, 2018 #6

    Just

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    I have my furnace and water heater in a utility room that will also have shelfs for storage. Should I put a heat reg in there?
     
  7. Jan 15, 2018 #7

    Snoonyb

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    You can add a damper at the wye, as well as an adjustable register to control demand.

    5 air changes per hour is a standard, however, you can get off into the weeds when you take into account what type of glazing, the amount as a % of the areas sq. ftg., as well as the N, S, E & W orientation. All of which can affect demand.
     
  8. Jan 15, 2018 #8

    Snoonyb

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    Not necessarily, however your comfort heating appliance should be a closed system and independent of the hot water heating appliance.
     
  9. Jan 15, 2018 #9

    Just

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    Yes there independent just in that same room
     
  10. Jan 15, 2018 #10

    bud16415

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    My furnace sits in the basement next to my water heater and the heating system is a closed loop to the upper floors. The basement has a door and would get quite cool in the winter months.

    I cut a hole in the main trunk leaving the furnace and installed an adjustable grate. I keep it cracked just a little and it helps warm the basement.

    I think what you are asking is similar you think you might want a little heat in your utility room. I would wait and see as you will get some heat escaping off the furnace and ducts. If it is not to your liking add one like I did. Worse thing that could happen is you would leave it closed.
     
  11. Jan 15, 2018 #11

    Just

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    Thank bud that's what I was trying to ask. Sorry if it didn't come across like that. I think I have it figured out thank you
     
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