DIY Home Improvement, Remodeling & Repair Forum > Appliances > HVAC > Size of intake vent?





Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old 05-09-2013, 03:25 PM  
Jungle
Senior Member
 
Join Date: May 2013
Posts: 137
Liked 12 Times on 10 Posts
Likes Given: 4

Default Size of intake vent?

If the intake is 14" x 8" to the furnace does the vent size have to be bigger? Does it really need a basin to catch air? I'd like to replace the old tin work because i think the air intake is too low and collects dust. I want to continue that same size of 14x8 intake vent and reposition the intake vent inside the stair case higher up from the floor. As it is now it is about 30" x8" which seems overkill to me and is dust trap.



__________________
Jungle is offline  
 
Reply With Quote Quick reply to this message
Old 05-10-2013, 07:48 AM  
CallMeVilla
Senior Member
 
CallMeVilla's Avatar
 
Join Date: Feb 2010
Location: San Diego
Posts: 1,054
Liked 266 Times on 216 Posts
Likes Given: 105

Default

Hi Jungle. Welcome to the Fun House ... I'd like to see pics if you could post them (this is a standing rule for inquiries). As I read what you said, I wonder: Is there a filter on your unit? If so, dust would be captured. You should know that intakes, feeds and returns are engineered and sized to optimize the performance of HVAC. However, simple repositioning the intake (return?) should not be a problem but reducing its size would be a problem.



__________________
CallMeVilla is online now  
 
Reply With Quote Quick reply to this message
Old 05-10-2013, 09:32 AM  
nealtw
Senior Member
 
Join Date: Nov 2010
Location: vancouver, b.c.
Posts: 7,694
Liked 540 Times on 489 Posts
Likes Given: 998

Default

If you do that you will only be using one cavity in a 2x4 wall so you would be down to 14 1/2x 3 1/2. I beleive the return should be more than the total of all the heat vents

__________________
nealtw is offline  
 
Reply With Quote Quick reply to this message
Old 05-10-2013, 10:22 AM  
Jungle
Senior Member
 
Join Date: May 2013
Posts: 137
Liked 12 Times on 10 Posts
Likes Given: 4

Default

The thing is the tin work was installed 30 years ago and i have upgraded the with new hi-eff furnace. There is a filter of course but that is the problem too much dust getting in there. The 30"x 8" intake is beside the stairs and uses the space between the joists in the basement as the basin, i think it is drawing some air from the basement too, so i want to rebuild the whole thing. I don't see the point of this basin, is it necessary?
If the intake is 14" x 8" then continue the vent up through the floor, long as it is not smaller then okay right?

__________________

Last edited by Jungle; 05-10-2013 at 10:28 AM.
Jungle is offline  
 
Reply With Quote Quick reply to this message
Old 05-10-2013, 11:40 AM  
nealtw
Senior Member
 
Join Date: Nov 2010
Location: vancouver, b.c.
Posts: 7,694
Liked 540 Times on 489 Posts
Likes Given: 998

Default

I'm not a HVAC guy so take it for what it's worth. Not sure what you mean by basin. They use the cavities between the studs or floor joists as duct work so to calculate the square inches you measure the cavity. So the grill and the cavity should be simular size to the intake at the furnace. If you are shortening the run and making it have less corners you will increase air flow.
Not sure if anything here will help for dust, as your filter is at the furnace some dust will alway collect in these areas. If you have heat registers in the basement, there should be a return from there.
I hope some of that helps.

__________________
nealtw is offline  
 
Reply With Quote Quick reply to this message
Old 05-18-2013, 04:40 PM  
keepinitcool
Junior Member
 
Join Date: Jan 2013
Posts: 27
Liked 9 Times on 7 Posts
Likes Given: 6

Default

I take it this isn't the only return air for the furnace? You need to have the same square inches of return as you do of supply. So say you are bringing 2 6" runs into your bedroom, this calculates to around 56 square inches of supply. You need 56 square inches (or preferably more) of return. I would put a 8x8 return (64 sq in), or a more common size 10x8 (80 sq in) in that room. So to answer your question, a 14x8 return (112 sq in) would be sufficient in a room being supplied with 3 6" runs, 2 8" runs, 2 6" and 1 8" run, 1 10" and 1 6" run, 1 10" run,
1 8" run, 1 6" run, and so on down the line. Keep it the same or more. To find square inches of round duct take the radius and square it and multiply it by pi (3.14). 8" round would be (4x4)3.14=50.24 square inches. Hope this helps you out!



__________________
keepinitcool is offline  
 
Reply With Quote Quick reply to this message
Reply


Quick Reply
Message:
Options

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter DIY Home Repair Forum Replies Last Post
Dryer Vent Size Mismatch rdb90 General Home Improvement Discussion 3 04-01-2013 06:53 PM
Bathroom exhaust fan. Is it ok to vent it through attic & up to ridge vent? lola123go General Home Improvement Discussion 9 05-13-2010 03:58 PM
Can I attach filter to intake vent? ilyaz HVAC 5 03-09-2010 09:40 AM
Strange question about intake vent? Hamlet123 HVAC 2 03-08-2010 09:58 AM
Actual size of oval type B vent pipe joybird HVAC 0 10-25-2009 08:54 AM