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-   -   Where do I start? (http://www.diychatroom.com/f17/where-do-i-start-5244/)

manderson 12-06-2006 11:25 AM

Where do I start?
 
Hi,

I am remodeling my house. I paid an HVAC guy to do calculations for sizing my furnace for the second story. Based on what he said, I have selected these units:

2fl furnace: GCH90703BXA
Goodman, Downflow/Horizontal, Two Stage/Multi-speed single
stage thermostat, 93%, 70000BTU, 12CFM, 17.5W X 28D X
40H, Low Nox


2fl Coil: CHPF3636B6A
Goodman, Horizontal A-Coil, Painted, Florator, 3 nominal tons,
fits 17.5 inch furnace cabinet, R-22


2fl Cond: GSC130301A
Goodman, Split System, Condensor R-22, 13 Seer, 2.5 tons,
208/230 1phase


He suggested that an extended plenum design was best for my situation. (the attic is being finished, the first floor is already finished. I've drawn a floorplan with possibly supply/return ducts that you can look at here:


http://i54.photobucket.com/albums/g102/mattanderson1/2ndfloorEastwallextendedplenum.jpg



The HVAC man I was getting help from isn't interested in helping anymore. My guess is that he just wanted to make the sale.


What size vents should I be installing? What size supply should be used with a 4x10 vent? with 2 4X10 vents? How do I figure out the appropriate plenum size?


Where do I start?

Matt

manderson 12-06-2006 12:30 PM

Do residential HVAC installers typically use dampers on all lines to pressure balance the system or do they actually take the time and do the calculations to figure pressure balancing through duct lenth/sizing? Should I bother worrying about doing it that way or should I just use 8' ducts with dampers and worry about balancing later?

Matt

#CARRIERMAN 12-06-2006 12:39 PM

Hi manderson

I like to calculate the cfm for a balanced system, but putting dampers in is not a bad idea. If they have a balance hood, they can tune the system for perfect air delivery if it has dampers. Let me know if I can help further.

Good luck
Rusty

acefurnacefixer 12-06-2006 06:27 PM

Quote:

Originally Posted by manderson (Post 26063)
Do residential HVAC installers typically use dampers on all lines to pressure balance the system or do they actually take the time and do the calculations to figure pressure balancing through duct lenth/sizing? Should I bother worrying about doing it that way or should I just use 8' ducts with dampers and worry about balancing later?

Matt

Most places in the USA dampers are required by code.You should have a main trunk line ( size is detrmined by a/c capacity), The trunk line should exstend as far as needed to reach most first floor heat runs. There should be no heat runs 18 inches from the end of the trunk line. Additional trunk lines can branch off main line as needed.

Hope this helps.


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