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 01-28-2013, 10:58 PM   #1
Newbie
 
Join Date: Jan 2013
Posts: 2
Share |
Default

Residential HVAC system upgrades


1. Why aren't Horizontal Slab Coils used in residential A/c Systems if room permits? About the same cost but less restrictive in flows.
2. If I understand the 'Equal Friction Duct Sizing' correctly, all trunks are sized to the same friction factor with the branches adjusted to achieve the same friction loss of the longest branch.
I'm still a little hazy in how to figure the trunks and adjusted branches for a duct upgrade.

IdKid is offline   Reply With Quote
Old 01-29-2013, 04:48 AM   #2
An old Tradesmen
 
Join Date: Oct 2008
Location: PA
Posts: 25,027
Default

Residential HVAC system upgrades


They are used in residential. They're common in some areas, and not in others.

Your correct on friction rate. Trunk lines are all sized to the same friction rate, and as air is remove by supplies, when the velocity drops by 200 to 300 FPM, you reduce down to a size that gets it back up, but is still at or just under the friction rate you need/want. Supplies are ran out at what ever the friction rate came out to for the TEL for the CFM the room/area needs.

beenthere is online now   Reply With Quote
The Following User Says Thank You to beenthere For This Useful Post:
IdKid (01-31-2013)
Old 01-31-2013, 07:00 PM   #3
Newbie
 
Join Date: Jan 2013
Posts: 2
Default

Residential HVAC system upgrades


Thanks, this has helped in the duct design math. To check, so the rest of my branches have the same pressure loss, the combined losses (of the flow path) of the trunk and a branch, should equal the combined losses of the longest branch.?
IdKid is offline   Reply With Quote
Old 02-01-2013, 04:18 AM   #4
An old Tradesmen
 
Join Date: Oct 2008
Location: PA
Posts: 25,027
Default

Residential HVAC system upgrades


Only the longest supply will have the loss of the TEL. The other ones will have the same per 100 foot of TEL, but will have a lower TEL. Balancing dampers are used to lower the air flow in the shorter branches that get too much air.

Not uncommon for a duct system to have a TEL of 300 foot plus or minus on the longest branch, and have a short branch with only 70 foot of TEL. But both are sized the to the same friction rate.
beenthere is online now   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
Replace just the Cooling Unit for Condo HVAC System acj74 HVAC 19 07-22-2012 02:03 PM
1 year old HVAC system not working designSTL HVAC 7 07-02-2012 08:44 AM
Goodman HVAC system blower stuck on? OhNoes HVAC 14 09-03-2011 07:32 PM
advice please! - new TRANE HVAC system ACtawk HVAC 2 10-07-2010 04:25 PM
Is 1/2 Pex more restrictive than 1/2 copper? twilightcall Plumbing 19 06-24-2008 07:32 AM




Top of Page | View New Posts

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