DIY Home Improvement, Remodeling & Repair Forum > Appliances > HVAC > HVAC design flaw?




Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old 08-29-2010, 11:43 PM  
rblaine
Junior Member
 
Join Date: Aug 2010
Location: Sacramento, CA
Posts: 2
Default HVAC design flaw?

Hello,

New to this forum. I hope someone out there might have some advice. My home was built in 1999, so it's not that old. 2 story 2800 sq ft. Has always had issues with the temperature being 10-12 degrees different between up and down. There is only one thermostat upstairs. I just avoided being downstairs during the winter. My wife and I married in 2004 and she complained about the difference and now we have some money to get it fixed. After having two contractors take a look at what I have, they both tell me the ducting is designed wrong. There are only two returns, 20x25 and 18x18, which they told me will allow only a little more than 1200 CFM and my 5 ton system needs 2200 CFM. So i need to install a new return and then install a zone system with a thermostat downstairs. The whole thing will cost $10K. My question is shouldn't the builder be responsible for this since it's appearently a design flaw? Any advice would be greatly appreciated.



__________________
rblaine is offline  
 
Reply With Quote Quick reply to this message
Old 08-30-2010, 05:28 AM  
kok328
Supporting Member
HRT_SUPPORTER.png
 
Join Date: Nov 2007
Location: Grand Blanc, MI
Posts: 2,195
Liked 109 Times on 95 Posts
Likes Given: 64

Default

I don't know if the builder would be liable or not but, chances are pretty good that the builder is long gone.



__________________
kok328 is offline  
 
Reply With Quote Quick reply to this message
Old 08-30-2010, 05:41 AM  
oldognewtrick
Moderator
HRT_MODERATOR.png
 
oldognewtrick's Avatar
 
Join Date: Jul 2009
Location: Nashville, TN
Posts: 5,411
Liked 459 Times on 382 Posts
Likes Given: 145

Default

Typically a builder will warrant a structure for a period of 1 year, unless you can prove willful intent to defraud, you are probably out of luck. A lot of contractors rely on their sub-contractors to provide and install systems. A lot of them don't fully understand the dynamics of house construction. You will spend a lot more than 10K trying to prove and recover the cost of fixing the original system.

__________________
oldognewtrick is offline  
 
Reply With Quote Quick reply to this message
Old 08-30-2010, 09:17 AM  
rblaine
Junior Member
 
Join Date: Aug 2010
Location: Sacramento, CA
Posts: 2
Default

Thanks for the replies. I was thinking that since car issues that are a design problem are repaired by the maufacturer (think Toyota) even decades after the car was built, the same might apply to an improperly built/designed HVAC. In my view this is something I would not have detected within the one year warranty. The builder is still around, so I'm thinking I might just ask him about it and maybe he can at least help me out with lower cost.

__________________
rblaine is offline  
 
Reply With Quote Quick reply to this message
Old 08-30-2010, 03:26 PM  
kok328
Supporting Member
HRT_SUPPORTER.png
 
Join Date: Nov 2007
Location: Grand Blanc, MI
Posts: 2,195
Liked 109 Times on 95 Posts
Likes Given: 64

Default

So would it be the builder (general contractor), the subcontractor or the local code inspector who signed off on the build?
Unfortunately, comparing automobiles and homes are like comparing apples and oranges when it comes to defects. Not to mention that the 1yr home warranty applies only to the original owner.

__________________
kok328 is offline  
 
Reply With Quote Quick reply to this message
Old 10-05-2010, 10:11 AM  
om55
Junior Member
 
Join Date: Oct 2010
Location: marion, In.
Posts: 5
Default

your probably not going to get anything from them and what you need is to find an affordable answer to your problem. have you asked your heating contractor about zone dampers with different controls that would shut off air to one section and let it continue in the other. I would think that an honest contractor could do that for less than ten grand. granted the duct work may still be not the way it should be but make it work now and rework the duct when it comes time to replace the whole unit.

__________________
om55 is offline  
 
Reply With Quote Quick reply to this message
Old 10-20-2010, 06:02 PM  
classic
Junior Member
 
Join Date: Apr 2006
Posts: 9
Default design problem

An excellent rule of thumb for return sizing is filter length x filter width x 2 = capacity, so 20 x 25 x 2 = 1000 cfm and 18 x 18 x 2 = 648. You have a nominal capacity of 1648 cfm and a 5 ton unit needs 2000, so you are 20% undersized.

Your real problem is heat trandfer 101 - hot are rises, cold air falls.

Lets pretend that your 2800 sq ft house is the same up and down.
Each floor is 1400 sq ft, so you need the same ammount of air for each floor,
right?

WRONG!!!!!
Hot air rises, so in the winter you need about 70% of the heat downstairs because the downstairs heat will take care of the upstairs.

Summer is just the opposite. The cold air downstairs pushes the heat upstairs, and the attic is hot as hell, so you need 65% of the cold air upstairs

you need some sort of damper system to make the switch between summer and winter needs.



__________________
classic 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
Bar design/ideas seanysean General Home Improvement Discussion 5 04-05-2010 11:05 AM
New Design TxBuilder HouseRepairTalk Website Help 3 10-06-2009 01:17 PM
Replacement window - Flaw in glass StrayKatt Windows and Doors 1 08-24-2009 03:40 PM
Poritco Design Help! robb01 General Home Improvement Discussion 2 07-16-2009 05:30 AM
Slab design ronbu General Home Improvement Discussion 1 10-26-2006 12:09 PM