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 03-19-2011, 10:14 AM   #1
Newbie
 
Join Date: Dec 2008
Location: Denver, CO
Posts: 18
Share |
Default

cold air intake from outside to furnace...


Our house was built in 1968. Yesterday a furnace guy was out to do a general checkup. He pointed at that we have:

1) Normal cold air return from all throughout the house
2) Cold air intake from outside piped directly in to the furnace
3) Makeup air vent in furnace room

He basically said #2, the cold air from outside directly in to the furnace, was "what they did 40 years ago" and was basically killing our furnace efficiency, since on the coldest days it was pulling in and having to heat outside air, possibly down to 10 below on our lowest days.

I'm inclined to believe him, however I also just wanted to get a second opinion before removing it and letting the furnace run on only return air from the house and the makeup air vent. Anyone know what the actual "code" is on that or where I can look to find it?

sspeed is offline   Reply With Quote
Old 03-19-2011, 11:32 AM   #2
Hvac Pro
 
Join Date: Nov 2008
Location: Winnipeg, Canada
Posts: 9,408
Default

cold air intake from outside to furnace...


Some homes need that fresh air pipe to get rid of excess moisture in the house, cooking smells, animals smells, cigarette smoke etc. We use a motorized damper in it to open it when only the heat is on. Google: Hoyme damper. If you shut it you may create a problem. It should have a damper in it which you can close to try living w/o it. I would not remove it.

http://www.hoyme.com/

__________________
"Cut it twice and it is still too short".
yuri is online now   Reply With Quote
Old 03-19-2011, 11:37 AM   #3
fabrk8r
 
fabrk8r's Avatar
 
Join Date: Feb 2010
Location: Iowa
Posts: 849
Default

cold air intake from outside to furnace...


Is your furnace 43 years old? I doubt it.

How is your furnace vented? If it's vented with PVC pipe it's a high efficiency furnace and the air supplying the furnace is called "combustion air" and has nothing to do with the air that is circulated through your home. Combustion air is supplied to the furnace from outside to allow combustion of fuel without pulling air from the structure and sending it out the flu. It is required by code is a lot of places now.

Now, having said that, it was common in older systems to have outside air supplied as "make-up air" to add air to the room where the furnace or other fuel burning appliance was located. This method also did not really affect the efficiency of the furnace a whole lot either, but it did add some cold air to the structure. Since your outside air is being piped directly into the furnace I'm guessing that it's combustion air and not make-up air.
__________________
"The physician can bury his mistakes, but the architect can only advise his clients to plant vines." -- Frank Lloyd Wright
fabrk8r is offline   Reply With Quote
Old 03-19-2011, 11:43 AM   #4
Experienced
 
Jackofall1's Avatar
 
Join Date: Dec 2010
Location: Southern Michigan
Posts: 2,822
Default

cold air intake from outside to furnace...


When you say, "Piped directly into the furnace", where exactly does it go, into the return air, or into the area of the combustion chamber?

Either way, this is bringing in air being used for combustion for all gas appliances, as well as exhaust sources such baths and kitchen.

Add a damper if there isn't one, but I wouldn't remove it.

Mark
__________________
When its all said and done there is usually more said than done
Jackofall1 is offline   Reply With Quote
Old 03-19-2011, 11:43 AM   #5
Jack of all trades
 
danrb007's Avatar
 
Join Date: Jan 2011
Location: Colorado/Wyoming
Posts: 73
Send a message via Yahoo to danrb007
Default

cold air intake from outside to furnace...


A trick I have used for the fresh air supply is pipe it into a 5 gallon bucket. have the end of the pipe sitting about 4 or 5 inches from the bottom. This will cut down tremendously on the cold air coming in from outside. The cold air stays at the bottom of the bucket since cold air sinks and warm air rises.
danrb007 is offline   Reply With Quote
Old 03-19-2011, 01:15 PM   #6
Member
 
Join Date: Oct 2009
Location: Nebraska
Posts: 2,362
Default

cold air intake from outside to furnace...


Outside air piped to the return is called fresh air/make up air. It's to equalize the negative pressure on the house from bath fans, drier vents,range hoods ect. By sticking in the return the air gets conditioned before dumping in the house. Without it the outside air will sneak in every crack and crevis,still the same amount but unconditioned.

Vents cut into the wall or a pipe just placed in the utility room is called combustion air. It supplies the oxygen for the fires to burn properly.
Marty S. is offline   Reply With Quote
Old 03-19-2011, 03:06 PM   #7
how
Member
 
Join Date: Feb 2011
Location: Vancouver BC
Posts: 1,491
Default

cold air intake from outside to furnace...


Are you are talking about a fresh air line that is passive (going from the outside and terminating within 18" of your burners) or active ( going from outside to the return air plenum with a vent opening at the furnace in the supply side plenum. You can't mess with either of these ( although the idea of adding a spill bucket to the passive system does help) systems without running the risk of co & co2 spillage into your house unless you have a mid or high efficiency furnace..
how is offline   Reply With Quote
Old 03-19-2011, 05:41 PM   #8
Newbie
 
Join Date: Dec 2008
Location: Denver, CO
Posts: 18
Default

cold air intake from outside to furnace...


Thank you for all of the replies. I'd have to guess the furnace is about 15 years old... Sounds like I should leave it...

To clarify:
What I was calling cold air intake comes from outside the house, through 4 inch pipe, in to the return about 3 feet from the plenum.

Then, in the same room, there is a 4in vent right in the wall that just dumps in to the room, I assumed that was the make-up air?
sspeed is offline   Reply With Quote
Old 03-19-2011, 07:26 PM   #9
Hvac Pro
 
Join Date: Nov 2008
Location: Winnipeg, Canada
Posts: 9,408
Default

cold air intake from outside to furnace...


The one in the duct we call fresh air or ventilation air. The other bringing air into the room for the furnace burner is called combustion air. 4" into the return duct is quite small and just enough to bring in some ventilation/fresh air air w/o costing that much to reheat so I would leave it alone. Your guy was wrong. 40 yrs later we still bring in air for ventilation but we use a minimum 5" pipe and put a motorized damper on it.

__________________
"Cut it twice and it is still too short".
yuri 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
furnace blows cold air but burner is workin drewhart HVAC 9 01-19-2011 08:22 AM
Trane XR 80 furnace blowing cold air as117 HVAC 1 11-28-2010 10:53 PM
fresh air intake for furnace Red Squirrel HVAC 6 05-21-2010 09:32 PM
new furnace - house is STILL cold qchawkfan Building & Construction 6 01-11-2010 09:30 PM
Furnace blowing cold air. rileyc HVAC 4 02-19-2009 02:18 PM




Top of Page | View New Posts

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