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 03-01-2012, 12:45 AM   #1
Member
 
Join Date: Oct 2011
Location: Phoenix, AZ
Posts: 113
Rewards Points: 77
Default

Ductwork - Two companies have two different ideas. What to do?


A little background. I had my rooftop AC replaced a few years ago by Company 1. They came highly recommended and seemed to do an OK job. We oversized the unit in anticipation of building an addition (they suggested a 2.5 or 3 ton unit and i selected a 3.5 ton unit). Later I had them do some duct work for a back room that didn't have an air supply. That duct has never functioned well, but they told me it wouldn't from the get go (that it would only improve things a bit).

Now I'm building the addition and its time for mechanical. Company 1 came in and looked at everything and suggested they would tap into the main air supply box and run flex duct to the addition (a bathroom/closet combo of roughly 300 square feet). The told me they would run right off the drop box in the same way they ran the duct work for the room I had them add a supply to...the one that doesn't cool well. I need the addition to be done right and be comfortable, so I'm leery. They want $2000 to do the work. You can see a diagram of what they are suggesting in picture one.

Company 2 came and looked and says the way the original duct was run (house built in 1953) won't allow them to properly cool the bathroom addition and that I will get a similar result to the duct run to the other room a couple years ago, even with an air scoop. They propose to cap the main supply line/jack coming down from the roof and cap the main duct as well. They would then use the supply line/jack as a mixing box/plenum and run three flex lines (various sizes) - one to the room that gets poor air, another to the main duct (which is quite large and serves 4 rooms) and a third to the bathroom addition. They say this is the only way to equalize the distribution since the original ducting wasn't designed to be tapped into. Company 2 said they would probably charge $500 to do the work Company 1 suggested (but they wouldn't guarantee the work)but that if I want it done right, they will guarantee the work for more $$ or course. Please see diagram number two.

What do you think?? I really want this done right the first time. System has more than enough capacity. This is a ducting physics question only. Thank you.

Company 1's Plan


Company 2's Plan

JeepNick is offline   Reply With Quote
Old 03-01-2012, 02:53 PM   #2
Part of the Clover Leaf
 
Join Date: May 2011
Location: NW Burbs of Detroit Mi.
Posts: 1,107
Rewards Points: 500
Default

Ductwork - Two companies have two different ideas. What to do?


Can't say as I like either plan.

hvac5646 is offline   Reply With Quote
Old 03-01-2012, 04:07 PM   #3
Member
 
Join Date: Oct 2011
Location: Phoenix, AZ
Posts: 113
Rewards Points: 77
Default

Ductwork - Two companies have two different ideas. What to do?


I realize the ideal solution would be to rip out the main duct, build a new mixing box and run lines to new registers in every room - Company 2 even suggested it. This isn't an option right now.
JeepNick is offline   Reply With Quote
Old 03-01-2012, 08:29 PM   #4
Member
 
Join Date: Oct 2011
Location: pa
Posts: 4,437
Rewards Points: 2,188
Default

Ductwork - Two companies have two different ideas. What to do?


have to agree with hvac5646 don't like either one...but if changing out the ductwork is not and option.. then ...ask either company you go with to address your low air flow condition..... keep in mind your own words .you want it right...
ben's plumbing is offline   Reply With Quote
Old 03-02-2012, 08:49 AM   #5
Part of the Clover Leaf
 
Join Date: May 2011
Location: NW Burbs of Detroit Mi.
Posts: 1,107
Rewards Points: 500
Default

Ductwork - Two companies have two different ideas. What to do?


I have said it before and I will say it again...square boxes with flex give very poor performance. Especially tapping into existing duct. The existing system is not sized for the addition...in most cases it is probably border line for the existing structure.

Either put in new duct system or condition the addition with a separate system.
hvac5646 is offline   Reply With Quote
The Following User Says Thank You to hvac5646 For This Useful Post:
ben's plumbing (03-02-2012)
Old 03-02-2012, 09:50 PM   #6
Member
 
Join Date: Oct 2011
Location: pa
Posts: 4,437
Rewards Points: 2,188
Default

Ductwork - Two companies have two different ideas. What to do?


Quote:
Originally Posted by JeepNick View Post
I realize the ideal solution would be to rip out the main duct, build a new mixing box and run lines to new registers in every room - Company 2 even suggested it. This isn't an option right now.
be prepared to deal with a system that can be filled with problems if not corrected right now which can and will damage equiptment....just my 2 cents

ben's plumbing 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
A/C and Ductwork Efficiency Jessidog HVAC 1 07-29-2011 07:48 PM
Redecorating DD's room....thoughts, ideas? Looong. RealHouswifOfOK Interior Decorating 14 04-22-2011 06:19 PM
Attic Ductwork - Need some ideas RustedBrit HVAC 3 03-17-2011 03:05 PM
plastic ductwork vs. metal: acoustic duct liners jjpclev HVAC 5 02-26-2010 07:29 PM
Moving ductwork to accomodate finished basement Badfish740 HVAC 1 01-13-2010 03:11 PM




Top of Page | View New Posts

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