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Old 05-08-2012, 10:43 PM   #1
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Duct work design


I have no doubt I can install my duct work myself. I've looked and found some general over views on designing a duct work system however they are pretty generic and since a well designed system can be the gift that keeps on giving. My question is:

I've found some places on the internet that will design my duct work if I send them room dimensions and some other generic information. They want $250-$300 for doing this, seems pretty reasonable. However, I don't think they are asking enough questions. I'm worried I'd end up with something that would work, but not work as well as it could.

The house is completely gutted and I've done a lot of preliminary work to make it energy efficient, now is not the time to cut corners. So the question is should I find someone local who will do the design for me (which I know is going to be more expensive if I can even find someone to do it without getting the job of installing it). Or will they end up just taking room measurements, asking some generic info and giving me a design?

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Old 05-08-2012, 11:35 PM   #2
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Duct work design


You can research and ask questions here and get some informative ansers. That way you are educated.

You'll need to know what size system you have and each room's cfm (air flow) requirements.

Outside of that I'd believe going local so you can have them around to answer any concerns would be good.

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Old 05-08-2012, 11:53 PM   #3
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Duct work design


I considered the same thing with a gutted house of ours but chose to hire someone local. That saved me numerous days of work and allowed me to concentrate on other things.

You should ask your friends if they may know someone or have a licensed relative who does good work. I purchased a heat pump myself (online) and then had a mutual friend hook it up in addition to building our ductwork. It turned out very nice and I saved thousands.

Ralph
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Old 05-09-2012, 07:49 PM   #4
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Duct work design


yep until it breaks.......
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Old 05-09-2012, 08:48 PM   #5
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Duct work design


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Originally Posted by carmon View Post
yep until it breaks.......
Then we'll be here to give guidance in diagnosing the problem. Since this is a DIY site.
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Old 05-09-2012, 08:49 PM   #6
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Duct work design


right.... forgot that part.....
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Old 05-10-2012, 11:53 AM   #7
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Duct work design


Quote:
Originally Posted by HalfHand View Post
I have no doubt I can install my duct work myself. I've looked and found some general over views on designing a duct work system however they are pretty generic and since a well designed system can be the gift that keeps on giving. My question is:

I've found some places on the internet that will design my duct work if I send them room dimensions and some other generic information. They want $250-$300 for doing this, seems pretty reasonable. However, I don't think they are asking enough questions. I'm worried I'd end up with something that would work, but not work as well as it could.

The house is completely gutted and I've done a lot of preliminary work to make it energy efficient, now is not the time to cut corners. So the question is should I find someone local who will do the design for me (which I know is going to be more expensive if I can even find someone to do it without getting the job of installing it). Or will they end up just taking room measurements, asking some generic info and giving me a design?
It sounds like what you need is someone to design your trunk line, and give you an idea of where to put the branches.

Round duct comes is relatively generic sizes, so the question is how much of each size.

If you're installing in the attic (easiest) you essentially have one long run down the length of the house (trunk) with branches going to each room. These branches are going to be 6" pipe or flex (most likely) so the starting point is figuring out how many branches are coming off. You'll want the runs to be as perpendicular to the trunk as possible to minimize material costs as well as velocity loss.

You can get away with just one register per room if you size it (and the duct diameter properly) though sometimes it's just easier to put in two registers (usually near windows) on 6" dia runs.

Feel free to PM me if you have any specific sizing questions - there are also a few nuances to installing ductwork/running flex that make the job more complete.

EDIT: I should add that while it is an exact science, the real world rarely behaves in an exact manner and even perfectly designed systems need balancing at the register level (think of closing a couple vents in the car and the AC blowing harder out of the open ones.)
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Old 05-10-2012, 12:08 PM   #8
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Duct work design


Be careful it can cut you like a razor... You will need some lefts, rights, crimps, buttons, hand breaks, folding tool and duct stretcher.

William L. Cornett, PMP
Owner
Comfortech Heating and Cooling, LLC.
Cincinnati, Ohio
513-444-4444
www.mycomfortech.com
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Old 05-10-2012, 12:19 PM   #9
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Duct work design


Quote:
Originally Posted by comfortech View Post
Be careful it can cut you like a razor... You will need some lefts, rights, crimps, buttons, hand breaks, folding tool and duct stretcher.

William L. Cornett, PMP
Owner
Comfortech Heating and Cooling, LLC.
Cincinnati, Ohio
513-444-4444
www.mycomfortech.com

What's a PiMP certification after your name?
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Old 05-10-2012, 04:24 PM   #10
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Duct work design


Quote:
Originally Posted by comfortech View Post
Be careful it can cut you like a razor... You will need some lefts, rights, crimps, buttons, hand breaks, folding tool and duct stretcher.
buttons?

Button head rivets?
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Old 05-10-2012, 11:48 PM   #11
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Duct work design


If you are technically inclined you might like to try out the demo version of this software package: Right-Suite by http://www.wrightsoft.com/ You can layout your house quickly in the drawing mode, specifying the building materials, and it will calculate the load based on that and the weather (however, in demo mode it will only give you a preset location in Richmond VA). It can then automatically generate a duct layout and bill of materials, or you can enter one by hand and let it size it for you. I got results in a few hours, and its easy to tweak and play with alternatives. Also interesting to see the effects of different building materials on the load calculation.

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