Gas Furnace Vent Size - HVAC - DIY Chatroom Home Improvement Forum


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

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

Reply
 
Thread Tools Display Modes
Old 02-05-2010, 12:44 PM   #1
Project Addict
 
tjeieio's Avatar
 
Join Date: Apr 2008
Location: Salem, Oregon
Posts: 27
Rewards Points: 25
Smile

Gas Furnace Vent Size


I have a 90+ Rheem gas furnace. The contractor came off the unit with a 2" pvc vent pipe, but one foot later upped it to 4" for a 12 foot horizontal run to the outside of my house. I am confused as to why they would go from the furnace's 2" discharge to a 4" pipe. Why couldn't they just run with 2" all the way, since that is what comes off of the unit.

If it is related to the pitch of the pipe, could I keep with 2" if I went directly into the nearby fireplace flue and kept it mostly vertical?

Advertisement

tjeieio is offline   Reply With Quote
Old 02-05-2010, 01:26 PM   #2
An old Tradesmen
 
Join Date: Oct 2008
Location: PA
Posts: 26,551
Rewards Points: 4,740
Default

Gas Furnace Vent Size


What size furnace?

Is it a 4" pipe, or is it a 3" ID pipe?

It can not be vented into a chimney.

Advertisement

beenthere is online now   Reply With Quote
Old 02-05-2010, 01:44 PM   #3
Project Addict
 
tjeieio's Avatar
 
Join Date: Apr 2008
Location: Salem, Oregon
Posts: 27
Rewards Points: 25
Default

Gas Furnace Vent Size


I believe it is a 105,000 BTU furnace. You are correct, 3".
tjeieio is offline   Reply With Quote
Old 02-05-2010, 03:04 PM   #4
Member
 
Join Date: Dec 2009
Posts: 641
Rewards Points: 500
Default

Gas Furnace Vent Size


3" is most likely the right size for a 105mbtu furnace. make sure the pipe increases on a vertical section, not horizontal or it will trap condensate.
hvac benny is offline   Reply With Quote
Old 02-05-2010, 03:19 PM   #5
Project Addict
 
tjeieio's Avatar
 
Join Date: Apr 2008
Location: Salem, Oregon
Posts: 27
Rewards Points: 25
Default

Gas Furnace Vent Size


Yes - the transition is just before the elbow that turns horizontal.
tjeieio is offline   Reply With Quote
Old 02-05-2010, 03:56 PM   #6
Old Newbie
 
Join Date: Aug 2009
Location: Ottawa Valley, Eastern Ontario, Canada
Posts: 70
Rewards Points: 75
Default

Gas Furnace Vent Size


I do some work for a local Rheem dealer.
He vents all his furnaces that way.
I believe it's a Rheem requirement.
tinmanrob is offline   Reply With Quote
Old 02-05-2010, 04:45 PM   #7
An old Tradesmen
 
Join Date: Oct 2008
Location: PA
Posts: 26,551
Rewards Points: 4,740
Default

Gas Furnace Vent Size


Quote:
Originally Posted by tjeieio View Post
I believe it is a 105,000 BTU furnace. You are correct, 3".
Its vented properly then.

Your installer did his due diligence.

Advertisement

beenthere is online now   Reply With Quote
Reply

Tags
furnace , gas , hvac , size , vent


Thread Tools
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
return vent size change philip18 HVAC 7 10-25-2009 12:18 AM
Can I reduce the vent size? beth n rod HVAC 3 08-22-2009 01:22 PM
Foundation crawl space vent size problem Constant Improvement Building & Construction 15 01-15-2009 06:07 PM
Is my furnace a direct vent or power vent? wease HVAC 5 02-02-2007 08:55 AM




Top of Page | View New Posts