Is room air okay for my furnace?

The furnace went out this weekend. (No problem. Only 15 below zero... Fahrenheit, mind you... with winds howling over 30 miles per hour.) Turns out the intake pipe (that leads outside) was clogged. The technician lifted the pipe out of the socket where it connects to the furnace and moved it aside an inch or so, allowing the furnace to suck in air from the room instead. He assured me the furnace can operate just fine on room air until temperatures warm up outside (i.e. spring, which is weeks away) and the pipe clears, at which point I can reconnect it. My question: Is he right? Is room air just fine for my furnace? If so, then why was it designed to use outside air in the first place?
I'm also wondering why they put the exhaust pipe right next to the intake pipe, since it was probably steam from the exhaust pipe that clogged the intake pipe. Geez, the intake pipe must be sucking in exhaust all the time! That can't be good! Seems like they should be separated as much as possible...
RW
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Mon, 11 Feb 2008 08:42:49 -0800, MNRebecca wrote:

Inside air is fine and the piping was installed correctly.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
This shouldn't be a problem other than with the exhaust going outside (as it should) the inside air used for combustion will have to be replaced, and that means cold outside air will be drawn into the house where ever it can be - generally around doors and windows. If the furnace is in an unfinished basement the air is probably drawn in thru cracks and openings around the foundation, so the heat loss isn't as bad as it would be if the furnace is in a utility closet off a living area. This is in fact exactly how old-fashioned low-efficiency furnaces worked (and still do). Drawing combustion air from outside is a good energy savings measure with new high-efficiency furnaces.
The exhaust pipe on the other hand should NOT be disconnected in such a manner, for obvious reasons.
As for the location of the intake and exhaust pipes, the manufacturer has specs for how far apart these should be, and how far they should extend beyond the house, to prevent the sort of problems you are describing. If installed correctly the amount of exhaust sucked back in the intake should be minimal. Additionally, of your furnace is exhausting so much moisture that the exhaust is clogging the intake, it would seem there is either an issue with the installation, or with the furnace' functioning. While my 90% efficient furnace will produce some steam on cold days, I've never noticed any ice forming on either of the pipes. We haven't hit -15, but have been down near 0 with howling winds and high humidity.
Have you actually inspected the pipe to confirm you suspicion it is ice that is blocking it and not something else? If it is disconnected at the furnace it should be fairly easy to run a wire of fish tape up the pipe to see how far in the blockage actually is.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Good to know, thanks!

It's sealed to the furnace. Until this incident, I never quite knew what my builder meant when he said, "You can't get carbon monoxide poisoning with this furnace, it's sealed. :)

No, the technician did it. He was dressed and I was in layers of jammies. 15 below, 30mph winds. I'm not going out there myself until the weather moderates. Maybe next weekend.
Thanks!
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

one more thing.. (this is a different Mark by the way)
I would seal off the unused intake pipe that leads outside. This is because you said the outside opening was right near the exhaust pipe. If the intake pipe should clear itself one day and you are unaware, it will be open and can draw in the exhaust gasses CO etc into your house. Seal it off on the inside so you know it is sealed.
Mark
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Mark wrote:

Nobody else said it so I will- has anyone tried clearing the intake tube from the furnace room end, with a drain snake? Odds are it just an an animal nest or something, with maybe a layer of ice. On PVC pipe, it can't be stuck very hard, unless the tech who put it in was a slob, and left lots of burrs in the joints. If it is iced up, directing a hairdryer up there for a few minutes may be enough to clear it. The exhaust from a shop vac, or even a leaf blower (if you can narrow the output end down) may be helpful as well. (I use my leaf blower to clear downspouts when I am up there cleaning gutters.)
aem sends...
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

No one else has said this so as gas fitter I will if you are operating the firnace without the air intake hooked up and some one more than one told you it is okay suggest you find a new service person. I have put in 40 to 50 high efficent furnaces and never had one ice up as you describe . This can lead to carbon monoxide being sucked in to your house from the gas watertank possibly putting it out. If this service person worked for me he would be fired as he is an idiot.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
What a terrible disaster waiting to happen. Room air will kill your furnace, in a hurry. You need air from behind the garage, under the wood pile, and next to the bird bath. Your furnace is in such great risk, you are about to die.
Having started with a joke. Sure, the cellar air is just fine. You should (this doesn't seem intuitive) leave a window open a crack, if possible. The air has to come from some where. Formerly, it was coming in the PVC tube. Now, it may be coming down the water heater chimney.
A properly installed exhaust should be farther away from the house compared to the inlet. and usually pointed away. So, cycling back is seldom an issue.
--
Christopher A. Young
Learn more about Jesus
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I would be a little worried that if something was blocking the intake that same something might be blocking the exhaust too. Have carbon monoxide detectors installed? Trust them with your life? Might be a good idea to go figure out what is causing that blockage.
Steve B.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.