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  1. #1
    I am a commercial plumber and have been for 15 years. I was a commercial pipefitter for about 5 of those years and really, truly understand the heating and cooling ends of HVAC. Its ductwork I dont understand. Im not looking for a handout or anything like that. Im a tradesman as much as most of you are. Here is my problem... I just bought a cape cod that is 2 years old, the cape(upstairs) wasnt finished. I am finishing it now and have absolutely no clue on what size duct to run up to the cape part of the house. I have been looking for 2 weeks on this darn internet trying to find "the answer". If someone could give me a website....any clue as how to size this damn ductline I'd appreciate it.

  2. #2
    Join Date
    Aug 2003
    Posts
    1,841
    It is hard to tell with out looking.Call a hvac company let them look & lay it out for you.If you wont to do the work just see if you can pay for them laying it out but I would let them do the work so you will know it is right.

  3. #3
    Join Date
    Feb 2004
    Location
    chicago suburbs
    Posts
    4,422
    why don't you ask a tin-knocker on one of your jobsites.
    FILL OUT YOUR PROFILE!!

  4. #4
    Join Date
    Jul 2001
    Posts
    3,112
    Ask one of the other trades people for some help. Maybe even work out a barter if you like. Not a lot of ducting to go to the upper level of a Cape. The biggest problem is not having a chase or raceway for the ducts to go from under to over.

  5. #5
    Join Date
    May 2001
    Location
    Bennington, Vermont U.S.A.
    Posts
    13,864
    When you are a tradesman it is always better to get into a barter trade as previously stated.

    But just so you get a mental picture. Air is a substance just like water. You wouldn't run a 1/4"water line to feed a residence or would you run a 2" line to feed a residence.

    First thing you have to figure out is how many cfm of air that your furnace handles. Just for example say it is 1600 cfm. Now you figure out what percentage of the upstairs is in relation to your house. Say it is 25% of the total. Then take 25% of the total cfms that your have to work with.(1600). This would mean you need 400 cfm for upstairs. Then go to the supply house and get a ductsizer. The ductsizer will tell you the different size ducts that you can use which will handle 400 cfm. This is a very rough explanation of how to size ductwork. ( don't beat me up other HVAC guys.)

  6. #6
    Its been my experiance that putting a second system or zoning your current system would serve you better in the long run

  7. #7
    Join Date
    Dec 2002
    Location
    peoples republic of maryland
    Posts
    954
    Paddy is right. Add a new zone to your home with a seperate system for the upstairs only. You won't regret it. Have a reputable pro size (properly with a man-j) and install it.
    "The meek shall inherit the earth"
    "he that's walking with wise persons will become wise, but he that is having dealings with the stupid ones will fare badly" Proverbs 13:20
    "Pressure is something people feel when they don't know what their doing". Peyton Manning-superbowl MVP

  8. #8
    Thanks for the help guys. I talked to a tin-knocker today and he suggested I run the largest supply and return that I can fit in the chase. The chase is about 3 foot x 3 foot from basement to the 2nd floor. He recommend the largest duct then balance at the reggisters. He even hooked me up with a sheet metal company and told me of a place to get registers and grilles from a knowledgable salesman that could help me out. So this all sounds good to me so far. Im getting more comfortable about this project. Thanks for the help. If you have anymore suggestions feel free, I'd really appreciate it.

  9. #9
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Get it sized correctly,the largest size that will fit is not the way to go.

  10. #10
    Join Date
    May 2000
    Location
    Colorado flatland native
    Posts
    15,067

    He meant.........

    talk to a higher up tin knocker. Not th $8. an hour variety....... One who knows whats going on. "Put in the biggest duct you can fit" is the stupidest advice I've ever heard.

    Hey Beenie...... Its called a Ducky-lator.

    My doctor gave me six months to live, but when I couldn't pay the bill he gave me six months more.
    Walter Matthau

  11. #11
    Join Date
    Sep 2002
    Posts
    4,970
    I dont think the largest size you can get in the chase is much of an answer but then we dont know what the tinner they turned you on to will say. If he says the same thing then I would run. If he sizes it to the cfm you need then that sounds better.

  12. #12
    Man you guys are brutal! Ok, I know what a ductulator is and have used one in the past. I guess I need to research what equiptment I'm running and go from there. I need the manual j, that would answer alot of questions.

  13. #13
    Join Date
    May 2001
    Location
    Bennington, Vermont U.S.A.
    Posts
    13,864
    Okay, I guess you are not going to act like one of those hit and miss HO that we get here. They ask a question and then you never hear from them again.

    So tell us something we can use. What kind of furance do you have? Model and serial#? How many square ft. is the area that you are trying to heat? Is cooling involved in this system? Since you have a duct chase I am guessing that this is one of those modular or preframed homes. Which might mean that the furnace was sized for this unfinished area.

    A ductulator is the same as a ductsizer that I mentioned earlier. So you are going in the right direction. Putting in the biggest duct that will fit is bad advice. We do have to consider velocity too.

    We need the whole story then we can help you out here.

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