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Ductwork design/furnace sizing

Posted by PKugler (My Page) on
Fri, Feb 14, 14 at 13:19

Hello all! So here's the scoop. My wife and I are putting in a modular home this coming spring. It will be a 30x36 cape style with a 12/12 roof pitch. The upstairs come unfinished. Plan is for me to to finish it off. I'm pretty handy so not a problem, been there done that. But when it comes to furnace sizing and ductwork( home comes with none) I'm at a stand still. I have used my local hvac guys for new installs and such, but feel I get burned every time. Why I end paying 3-4 times than the next guy is beyond me. So I guess what my questing is, is there any outside(online) sourcing I can do for the ductwork system design if I can supply floor plans? And do the installs myself.

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RE: Ductwork design/furnace sizing

You have the determine the size of the HVAC system before you can design the size of the duct work.

The first step would be to do a heating and cooling load calculation. This is know in the industry as a Manual J calculation. There is software which has been designed to do this. You can get a homeowner's version for $50. This will calculate the amount of heating and cooling BTUs.

Once the loads are established, you will know how much air flow is required. There are software package for sizing the duct work (Manual D calculation), but you could do a hand calculation and use some rules of thumb to size the main duct work and branches.

RE: Ductwork design/furnace sizing


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