Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > HVAC

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Search this Thread Display Modes
Old 01-09-2012, 11:43 PM   #1
I ask the impossible!
 
Join Date: Aug 2010
Location: Royal Oak, Michigan
Posts: 1,061
Blog Entries: 7
Share |
Default

double cold air return to nowhere?


It's late so I'll make this short, in the pic below you'll see 2 flexible ducts going into a sheet metal enclosure of a joist cavity. Above this is my stairway, but there's nothing inside that this connects to. The other end of both of these ducts is the cold air return manifold of my furnace.

The duct on the left needs to go because the post shows where a beam will be coming through.
Attached Thumbnails
double cold air return to nowhere?-double-cold-duct-nowhere.jpg  

__________________
Please do NOT consider any "before" picture of my house as any kind of endorsement of any particular construction method. In fact, you should probably assume that if I post a "before" picture, I am posting it because I am soliciting advice on a proper replacement for one of MANY things done wrong by a previous owner.
WillK is offline   Reply With Quote
Old 01-10-2012, 12:05 AM   #2
Member
 
Join Date: Feb 2007
Location: NW Ohio
Posts: 804
Default

double cold air return to nowhere?


I will bet if you follow the panning, you will find that they go to a wall or floor return grille. doing away with them will cause your unit to have serious and potentially deadly problems.

harleyrider is offline   Reply With Quote
Old 01-10-2012, 12:10 AM   #3
I'm Your Huckleberry
 
Join Date: Mar 2011
Posts: 5,556
Default

double cold air return to nowhere?


How many return grills are in your home? You may need to relocate the one versus simply removing it.
__________________
Thanks.
Doc Holliday is offline   Reply With Quote
Old 01-10-2012, 07:14 AM   #4
I ask the impossible!
 
Join Date: Aug 2010
Location: Royal Oak, Michigan
Posts: 1,061
Blog Entries: 7
Default

double cold air return to nowhere?


Ahh.. okay, now that I've had some sleep I can get into more detail.

So, what is a little hard to see from the picture, the sheet metal enclosing the joist cavity terminates on the left side about where the strap hanging the gas pipe blocks the view. On the right side, it is considerably harder to see - the board that is supporting the floor joists, I haven't accessed the other side to look. Beyond that board is a triple 2x6 center beam, and I know that this enclosed joist cavity does not go to the center beam, so either that side is open or it closes before that. The sheet metal on the bottom has an open gap to the crawlspace at the board visible in the photo.

Assuming it's enclosed on both sides, which is one of those assumptions that should be reasonable - but in the case of this house, I've found that reasonable assumptions are often wrong - this would be a cold air return pulling something from somewhere inside the stair cavity.

Under the stairway to the second floor, there is a metal duct going to the front bedroom wall register. That is not what this is. That duct is served by a seperate duct.

There are no other duct work under the stairs.

For cold air returns, there are 2 returns on the first floor served by seperate ducts. The second floor has 2 supply registers, one in the wall of the front bedroom and the other in the floor of the rear bedroom, both served by their own ducts. There is one other floor grate at the top of the stairs which has no duct work, it's just a floor grate to the joist cavity.

Is it possible that these 2 cold air returns are intended to pull cold air returning from the floor grate on the second floor? Possibly. If that is their intended function, they can't be doing it very well because there are plenty of gaps in the stair treads and a very loose openning into the space under the stairs, and it's not clear what the air path is from the floor grate on the second floor.

One of those ducts has to move or be capped off.

At this point, I have no door to the front bedroom, it split in half at the hinges. I have 7' ceilings upstairs and the door openning is shorter than standard opennings, and in a year or two the whole second floor is coming off, so I'm having a little difficulty justifying to myself putting a new door on.. The other bedroom has a generous gap under it. (and no cold air return in either room anyway)
__________________
Please do NOT consider any "before" picture of my house as any kind of endorsement of any particular construction method. In fact, you should probably assume that if I post a "before" picture, I am posting it because I am soliciting advice on a proper replacement for one of MANY things done wrong by a previous owner.
WillK is offline   Reply With Quote
Old 01-10-2012, 07:33 AM   #5
Member
 
biggles's Avatar
 
Join Date: Jan 2008
Location: Long Island
Posts: 3,615
Default

double cold air return to nowhere?


how far away is the unit from those duct drops the return should basically be under the stat location is within a hallway so the stat can sense that return air..is that a cold crawl space.the back of the furnace should be consistant in size from the space 20 x 20 grilled.if that flex is sitting in a lower temperature area it will chill that return from the space.
biggles is offline   Reply With Quote
Old 01-10-2012, 08:57 AM   #6
I ask the impossible!
 
Join Date: Aug 2010
Location: Royal Oak, Michigan
Posts: 1,061
Blog Entries: 7
Default

double cold air return to nowhere?


There is a register heating the crawl space off of the heated air manifold. The ducts shown in the picture might be around a 5' run. There aren't really any hallways in the house, the stairs go up to the second floor to a landing that is maybe 30"x30" which has the floor grate in it, and the bedrooms are on the left and right as you are facing from climbing the stairs.
__________________
Please do NOT consider any "before" picture of my house as any kind of endorsement of any particular construction method. In fact, you should probably assume that if I post a "before" picture, I am posting it because I am soliciting advice on a proper replacement for one of MANY things done wrong by a previous owner.
WillK is offline   Reply With Quote
Old 01-10-2012, 09:25 AM   #7
I ask the impossible!
 
Join Date: Aug 2010
Location: Royal Oak, Michigan
Posts: 1,061
Blog Entries: 7
Default

double cold air return to nowhere?


So I'm thinking I don't know enough to say whether there was a good reason to run 2 cold air return ducts, but regardless it can't be any worse to stick with 2 cold air return ducts, so I will connect them both to a 6" wye and cap off one opening.
http://www.homedepot.com/h_d1/N-5yc1...atalogId=10053
http://www.homedepot.com/h_d1/N-5yc1...atalogId=10053
__________________
Please do NOT consider any "before" picture of my house as any kind of endorsement of any particular construction method. In fact, you should probably assume that if I post a "before" picture, I am posting it because I am soliciting advice on a proper replacement for one of MANY things done wrong by a previous owner.
WillK is offline   Reply With Quote
Old 01-10-2012, 09:31 AM   #8
I'm Your Huckleberry
 
Join Date: Mar 2011
Posts: 5,556
Default

double cold air return to nowhere?


Every furnace needs a certain amount of return air. One 6" run is nowhere near enough for any furnace.

What size furnace do you have?
__________________
Thanks.
Doc Holliday is offline   Reply With Quote
Old 01-10-2012, 09:41 AM   #9
I'm Your Huckleberry
 
Join Date: Mar 2011
Posts: 5,556
Default

double cold air return to nowhere?


This pdf is for heat pump systems but you can get an idea. I'm sure you could search the internet for required cfm (and duct sizes and grill registers to accomodate) for your sized system.

Scroll down to "flex duct return".
http://efficientcomfort.net/Rules_an...ct_Systems.pdf
__________________
Thanks.
Doc Holliday is offline   Reply With Quote
Old 01-10-2012, 09:45 AM   #10
I ask the impossible!
 
Join Date: Aug 2010
Location: Royal Oak, Michigan
Posts: 1,061
Blog Entries: 7
Default

double cold air return to nowhere?


Quote:
Originally Posted by Doc Holliday View Post
Every furnace needs a certain amount of return air. One 6" run is nowhere near enough for any furnace.

What size furnace do you have?
I think the 75 in the model number means it's a 75000 BTU unit.

There are 2 more 6" cold air returns besides the two pictured.
__________________
Please do NOT consider any "before" picture of my house as any kind of endorsement of any particular construction method. In fact, you should probably assume that if I post a "before" picture, I am posting it because I am soliciting advice on a proper replacement for one of MANY things done wrong by a previous owner.
WillK is offline   Reply With Quote
Old 01-10-2012, 09:53 AM   #11
I'm Your Huckleberry
 
Join Date: Mar 2011
Posts: 5,556
Default

double cold air return to nowhere?


I believe 75k btu is a 3 ton.

Here's some more related and interesting info if you care to get very technical.

http://www.mmmfg.com/pdfs/060601_CC-...tTechPaper.pdf
__________________
Thanks.
Doc Holliday is offline   Reply With Quote
Old 01-10-2012, 11:41 AM   #12
Member
 
Join Date: May 2008
Location: Near Philly
Posts: 1,986
Default

double cold air return to nowhere?


Doc, after reading that study, it seems that anything less than a 4% sag/compression of flex duct in an install would result in significant losses (increased pressure) of air flow vs. rigid metal. Might explain why my second floor bedrooms have such poor airflow:

double cold air return to nowhere?-squisheda.jpg
double cold air return to nowhere?-boota.jpg

Flex line squished between air intake/exhaust pipes and floor joist.
Connects to a boot in the wall cavity?
Any way of fixing this?
bob22 is offline   Reply With Quote
Old 01-10-2012, 11:59 AM   #13
Member
 
biggles's Avatar
 
Join Date: Jan 2008
Location: Long Island
Posts: 3,615
Default

double cold air return to nowhere?


that return has to come from the heated space anyplace else and your going to heat raw/unconditioned cold return air maybe bring the register duct out to the flex..instead of cramming that flex in the straighter the return the better the return and al has to be tight...furnace is going to suck air from any place it can... all types of connections on here http://www.bestbuyheatingandaircondi...ctworkmenu.htm

Last edited by biggles; 01-10-2012 at 12:02 PM.
biggles is offline   Reply With Quote
Old 01-10-2012, 12:54 PM   #14
I'm Your Huckleberry
 
Join Date: Mar 2011
Posts: 5,556
Default

double cold air return to nowhere?


Anything can be fixed, it's how you go about doing it that counts. It's a very poor install to begin with and definitely is an issue with performance, being strangled as it is.

I'd remove that run and put it in it's own joist away from those pipes.

__________________
Thanks.
Doc Holliday is offline   Reply With Quote
Reply


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 Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Adding on to cold air return agicr HVAC 13 03-27-2011 01:33 PM
Cold Air Return issue ra1185DIY HVAC 1 12-05-2010 03:21 PM
moving my cold air return Bill Smith Building & Construction 2 11-27-2010 10:35 PM
Need advice on cold air return mrlouie HVAC 4 10-09-2010 04:33 AM
Cold Air Return next to supply duct thebigbbm HVAC 6 09-21-2010 05:51 PM




Top of Page | View New Posts

Copyright © 2003-2014 Escalate Media. All Rights Reserved.