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Old 06-24-2012, 03:42 PM   #1
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Help Me Estimate HVAC Ducting Size...


Hello,

I need help estimating what size flexible HVAC ducting I will be dealing with for a project in a vacation home...

The house is a 3800 square foot, two-story home, with four bedrooms on the top floor. An AC unit is dedicated to each floor. I plan to install dampers to each of the bedrooms and it will be controlled via a 4-zone controller (I've got this part covered). The house location is rather remote, so I am forced to guess at what size dampers to buy. If I get it all wrong on this trip, then I can return the items and reassemble for the next. Your help will help my odds of not dropping a few F-bombs and getting it right the first time.

So, what is the most common size of HVAC ducting used to supply an average bedroom in this case? Yup, I know that there are so many variables, but give it your best shot...


More microchips than sense,
Dr. Z.

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Old 06-24-2012, 03:58 PM   #2
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Help Me Estimate HVAC Ducting Size...


".....getting it right the first time....."

You're doing all wrong.....You know what I'm talking about....Do it right first time....

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Old 06-24-2012, 04:48 PM   #3
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Help Me Estimate HVAC Ducting Size...


Your plan may already be wrong. I'm not sure how big your average size bedrooms are. Not sure how much window area your average size bedrooms have. Not sure which way they face. No bathroom on the second floor? What about the landing area, any air going to it?

Each bedroom its own zone? So how are you controlling air flow volume for the air handlers needs? What about short cycling?
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Old 06-24-2012, 07:14 PM   #4
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use hard pipe. i dont like to use flex. seen to many blow apart. less restriction on hard pipe.
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Old 06-24-2012, 07:15 PM   #5
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Help Me Estimate HVAC Ducting Size...


Quote:
Originally Posted by beenthere View Post
Your plan may already be wrong. I'm not sure how big your average size bedrooms are. Not sure how much window area your average size bedrooms have. Not sure which way they face. No bathroom on the second floor? What about the landing area, any air going to it?

Each bedroom its own zone? So how are you controlling air flow volume for the air handlers needs? What about short cycling?

I will be installing an Ecobee Smart-Thermostat as the main hub. It will then interface with three Ecobee Smart-Si thermostats, then a 4-zone damper controller. All of this techno geekery gives each bedroom their own thermostat control by regulating the individual area temperatures via opening/closing the dampers. It will basically be like having four independent AC units in one. HA, that is just the beginning of what it can do.

Anyhow, I just need to estimate what size the existing flexible HVAC ducting is so I can buy the right sized dampers...
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Old 06-24-2012, 08:22 PM   #6
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Help Me Estimate HVAC Ducting Size...


Man you just want some rule of thumb kind of answer right? 6 inch for a small bedroom, 7 inch for a medium size bedroom, 8 inch for a master bedroom
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Old 06-24-2012, 08:28 PM   #7
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10 inch with controlled dumper.....
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Old 06-24-2012, 08:35 PM   #8
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Help Me Estimate HVAC Ducting Size...


Quote:
Originally Posted by Zeigh View Post
I will be installing an Ecobee Smart-Thermostat as the main hub. It will then interface with three Ecobee Smart-Si thermostats, then a 4-zone damper controller. All of this techno geekery gives each bedroom their own thermostat control by regulating the individual area temperatures via opening/closing the dampers. It will basically be like having four independent AC units in one. HA, that is just the beginning of what it can do.

Anyhow, I just need to estimate what size the existing flexible HVAC ducting is so I can buy the right sized dampers...
Just go and look at the existing size duct. no guessing then. How are you going to prevent coil freezing from low air flow?
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Old 06-24-2012, 08:40 PM   #9
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He obviously doesnt care about that at this point. He probably forgot to measure his ducts before he left last time. Now he is going back (to a remote location) and does not wanna drive there with a bunch of wrong material. Im guessing he will take a bunch of 6,7,and 8 up there, hook it up, and return whatever he didnt use

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