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 09-13-2008, 07:18 PM   #1
Newbie
 
Join Date: Sep 2008
Posts: 1
Rewards Points: 10
Default

Nat. Gas B-Vent sizing


What is the best size B-vent stack for water heater? Replaced my furnace with hi-efficiency sealed combustion type so no longer exhaust it out the roof. So now have only the 40,000 btu gas water heater venting out the 5" stack about 18' vertical height in MN. Conflicting info from contractors said "code don't require change, so leave it" or from another "will have high condensation in MN cold weather so better reduce size". Plan on reroofing in next few weeks so would like to change it now if needed.
Or since water heater is probably 23 yrs old do I go for a power vented out the side wall new heater?

hiondetails is offline   Reply With Quote
Old 09-14-2008, 12:29 AM   #2
MacGyver
 
Join Date: Sep 2008
Location: Sparks NV
Posts: 17
Rewards Points: 10
Send a message via AIM to Kizzl775
Default

Nat. Gas B-Vent sizing


well if you gotta run a new pipe you will be fine with 4 in B-Vent. now on the otherhand if your gunna think about a direct vent for a few more dollars id look at like a rinnai tankless little costly but there sweet as hell it pushes like from 7.5 to 8.5 gallons a minute

Kizzl775 is offline   Reply With Quote
Old 09-14-2008, 07:16 AM   #3
oops, did I do that!
 
Join Date: May 2008
Location: mid michigan
Posts: 290
Rewards Points: 250
Default

Nat. Gas B-Vent sizing


If your water heater is 23yrs old, it wont be long before you have to replace it. Might want to do it now and not have to worry about it. 4in. is the most common for residential applications.

During cold weather the furnace will cycle on and off frquently during the day, and keep the vent or chimney warm and venting properly. Once that source of heat is removed, and vented elsewhere the water heater is the only source of heat and does not cycle as frequently, or not at all when water is not being drawn from it, and the vent or chimney cools off during the off cycle.

Once it does cycle on, warm/cold creates condensation. This condensation is acidic, and will attack the mortar of the chimney, or the metal in the vent. Typicaly a stainless steel liner is installed to prevent this. Maybe you should mention this to the furnace installer, and check with your local code enforcement to see if a liner is required. You may get another few years out of that old water heater. It will also come in handy when you do purchase a new heater, and give you another option to venting through the side wall.

Last edited by 8 Ball; 09-14-2008 at 07:22 AM.
8 Ball 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
Soffit Vent Sizing - Really Hot Attic dmo069 Roofing/Siding 7 12-04-2008 10:33 PM
Low-Slope Ventilation - Cobra Fascia Vent and Cor-a-Vent Roof-2-Wall vent atulc Roofing/Siding 7 08-22-2008 11:40 PM
Plumbing Vent size recommendations rlhed Plumbing 4 07-31-2008 01:01 AM
Where is the toilet vent?!?!? domgbrown Plumbing 4 01-11-2008 07:33 PM
Yoke vent for water closet kenlog Plumbing 4 07-13-2007 07:34 PM




Top of Page | View New Posts

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