Duct size


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Old 03-18-19, 10:08 AM
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Duct size

Replacing my furnace with high efficiency. I am not doing the install but am replacing some of the ductwork or all for that matter. Was wondering what size duct I should use. The bedroom currently has 6 metal and the kitchen as well. They are both 125 sq ft. Should I jump up to 7 pipe? According to all the CFM charts I looked at, 7 is the right size
 
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Old 03-18-19, 10:21 AM
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There are no generic charts for duct system design. And it’s not about guesswork or opinions.
Duct is layed out via room by room manual j calculation, used with a manual d.
This will tell you the heat load in each space.
Getting off subject but there should also be returns in each room except kitchens, laundry rooms and bathrooms.
 
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Old 03-18-19, 10:38 AM
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use the size that will move the amount of air you need for each room.
 
 

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