Furnace flue CO2 danger concerns

Reply

  #1  
Old 02-14-20, 01:03 PM
J
Member
Thread Starter
Join Date: Feb 2020
Posts: 3
Received 0 Votes on 0 Posts
Unhappy Furnace flue CO2 danger concerns

Please see the attached images of the problem.

I'm looking for an outsider's opinion on my furnace and the flue. We're currently looking to replace our 19-year-old HVAC system and have multiple sales reps coming in to look at our unit. One of the sales reps determined that my furnace was not safe to run and turned off my gas line that goes to my furnace.

I thought that was strange because I have a company that checks my unit and they looked it over about 3 months ago. With that said, I had a third company come in and they also agreed it was not safe to run. The third company said there is an unusual amount of exhaust escaping through the pipe and that it's not safe to run.

We moved into this house less than a year ago and this is the first I hear of this. This unit has most likely been like this for that last 19 years. I decided to buy a CO2 detector with a screen that displays the peak level of PPM. I put it in the AC closet and let the heater run. No CO2 was detected.

Here is the background info that may be helpful.
I live in south Texas. Mild winters and really hot summers. I live in a ranch-style two-story home. The unit is in an AC closet on the 2nd floor in the hall. The furnace is a RUUD Silhouette II and it's 19 years old. It has an induced draft blower. All the flue pipe looks to be B-type that runs into my attic and out the top of my roof. I did notice that the flue pipe is in no way screwed to the furnace and I can pull the pipe off the top of the furnace with very little effort.

Any advice is appreciated. Thank you in advance.
 
Attached Images   
Sponsored Links
  #2  
Old 02-14-20, 03:50 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 55,114
Received 585 Votes on 551 Posts
Welcome to the forums.

In the first picture..... is that the flue pipe just hanging over the 3" furnace exhaust port ?
That would allow a lot of exhaust to leak out.
In the second picture..... is that the flue pipe going directly thru the roof ?



 
  #3  
Old 02-14-20, 04:45 PM
user 10's Avatar
Member
Join Date: Mar 2004
Location: NA
Posts: 2,022
Received 39 Votes on 33 Posts
In the first picture..... is that the flue pipe just hanging over the 3" furnace exhaust port ?
That would allow a lot of exhaust to leak out.


I could be wrong, I believe that flue setup is used when the chimney or liner is too large for the btus of the furnace -> air goes into the gap and dilutes the exhaust to prevent condensation.

Kind of like the draft hood on a natural draft water heater.

Keep in mind, the venting of induced draft furnaces runs under negative pressure once the draft is established. If there's exhaust leaking out of there beyond the few seconds to establish a good draft, there's a chimney or b-vent problem.

That installation is not necessarily illegal. It''s hard to tell for sure

-----------
If the furnace itself is safe and exhaust problem can be corrected, i would hang on to that furnace. Will never re-coup the savings of going high efficiency in texas.
 
  #4  
Old 02-15-20, 03:50 AM
M
Member
Join Date: Sep 2019
Location: Canada
Posts: 918
Received 80 Votes on 75 Posts
Shutting off the gas may have been a salesman's trick to try and get you to buy now.

I would steer clear of that company.

The question is: how did they determine that there was a problem with the system?
I cannot see any degradation with the flue and it has run for years like this without a problem.
So I am skeptical.

One thing i did see is that screen up on the roof.
Is that supposed to be a cold air return?
Looks like it could use a cleaning.

 
  #5  
Old 02-15-20, 03:51 PM
J
Member
Thread Starter
Join Date: Feb 2020
Posts: 3
Received 0 Votes on 0 Posts
Hey,

Thanks for the input everyone. I attached two additional images. One is showing the rest of the flue running through the attic and into the roof. The pipe measures 5 inches in diameter. In the original pictures, you can see the bottom of that pipe sticking down through the ceiling of the AC closet.

The second image is the details of how the flue connects to the furnace (or lack thereof connection).

Yes, the pipe is just hanging over the exhaust port. I took a picture of that for greater detail.
The flue runs into the attic and out the roof. The picture inside the AC closet shows where the pipe goes out the top of the closet and into my attic.

The screen on the ceiling of the AC closet leads to the attic.
 
Attached Images   
  #6  
Old 02-15-20, 06:10 PM
Grady's Avatar
Forum Topic Moderator
Join Date: Jan 2005
Location: Delaware, The First State
Posts: 14,151
Received 19 Votes on 17 Posts
B-vent requires at least a 1" clearance to combustable materials. It doesn't look like you have that much. That connection at the furnace is just plain wrong. If you had to use a short piece of single wall & an adaptor to get up to the size of the B-vent, it would be better than the B-vent sitting loose on the exhaust of the furnace. If you can give us a model number of the furnace, maybe we can find an installation manual.
 
  #7  
Old 02-15-20, 10:05 PM
J
Member
Thread Starter
Join Date: Feb 2020
Posts: 3
Received 0 Votes on 0 Posts
I found this link that matches my model of the unit. The model number is UGPH-10EBRJR. It's a 100,000 BTU unit so according to the manual I found online it should be a 4 inch and requires a 3in to 4in transition. From the looks of this, it goes from 3 the inch outlet on the furnace to 4in and then 4 to 5inch.

Side note. The house was built in 1981. This furnace was put in around 2000. I'm guessing the old furnace used the 5-inch pipe and someone rigged this bad boy up to the original pipe. I also have a condensation issue with this pipe. It leaks at one of the elbows in my attic. Probably because the pipe is too big and is cooling off in the attic. That's my best guess.
 
  #8  
Old 02-16-20, 05:01 AM
Geochurchi's Avatar
Member
Join Date: Nov 2012
Location: USA
Posts: 4,212
Received 25 Votes on 24 Posts
Hi, does that duct with the screen on it have a fire damper on it? if not it will act like a flue pipe should a fire occur .
Geo
 
  #9  
Old 02-16-20, 06:30 AM
M
Member
Join Date: Sep 2019
Location: Canada
Posts: 918
Received 80 Votes on 75 Posts
Are you sure that the 5 inch is not actually a 4 inch but double walled.
 
  #10  
Old 02-16-20, 07:14 AM
Grady's Avatar
Forum Topic Moderator
Join Date: Jan 2005
Location: Delaware, The First State
Posts: 14,151
Received 19 Votes on 17 Posts
Unfortunately often when furnaces are changed the vent system is not properly redone.

With your furnace at nearly 20 years old & knowing you have condensate issues, there's a fair possibility there's a good bit of rust in the heat exchanger. At a bare minimum the heat exchanger needs to be cleaned & inspected. If still intact, the vent should be replaced with the proper fittings & pipe size.
 
  #11  
Old 02-16-20, 05:26 PM
H
Member
Join Date: Nov 2002
Location: Massachusetts
Posts: 1,822
Received 0 Votes on 0 Posts
just a quick correction

Theres no concern with CO2, you can breathe that all day long. We exhale CO2 ourselves. Our green plants love the stuff.
Now if your referring to CO, well thats a totally different gas, That gas will kill you. Now maybe, just maybe, one of these guys popped his combustion analyzer on it, and the CO was over 50 PPM, or he detected the conditioned space has CO, and just stopped there. Most people want free estimates and like they say "Theres no free lunch".
I think there should have been a thimble to keep the spacing away from combustibles and yank that flue completely out and start over with the proper sized pipes. This is of course after the heat exchanger is proven to be solid. 20 Years old, highly unlikely, especially with condensate issues. If it were mine I'd junk it, and that flue system with it. Unless your going to move soon.... Make sure it gets inspected by the city (permitted) if replaced.
 
Reply

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


Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: