Water Vapor in Flue Gases


  #1  
Old 01-31-07, 06:28 AM
B
Member
Thread Starter
Join Date: Jun 2006
Posts: 27
Likes: 0
Received 0 Likes on 0 Posts
Water Vapor in Flue Gases

Recently I had to replace all the galvanized exhaust pipe from my NG heater. Many parts had completely rusted through. I thought I had water coming down the chimney, but low and behold I find out that I have sooooo much water vapor in the exhaust that it condenses shortly after entering the chimney.... It drips back down the new exhaust pipe, leaking out the seams (I replaced with plastic pipe but did not glue it). I fill a 5 gallon bucket in a week.

What are my options for this problem? Do I seal all the joints and just run a drain line into the floor? I have never seen a problem this bad before. I'm not even sure why it would be condensing so quickly. The chimney is in the middle of the house. It should be warm.

Thanks,
Bill
 
  #2  
Old 01-31-07, 08:18 AM
Jay11J's Avatar
Member
Join Date: Sep 2001
Location: Rochester, Minnesota
Posts: 18,427
Likes: 0
Received 0 Likes on 0 Posts
How big is the flue pipe? and how long of a run going up?

Is it in the middle of the home or outside along the side of the house?

How many BTU is the furnace, and water heater?
 
  #3  
Old 01-31-07, 10:03 AM
B
Member
Thread Starter
Join Date: Jun 2006
Posts: 27
Likes: 0
Received 0 Likes on 0 Posts
Flue pipe coming out of the furnace is 2" and connects to a 5" chimney pipe. Vertical run of 2" is less than 3'. Vertical run of 5" is probably less than 30' from basement to roof of my ranch.

The Chimney is in the middle of the house.

125,000 BTU unit. There's no water heater involved or other appliance.

TIA,
Bill
 
  #4  
Old 01-31-07, 11:14 AM
F
Member
Join Date: Mar 2006
Location: Wet side of Washington state.
Posts: 18,495
Received 37 Likes on 29 Posts
Burning natural gas creates four molecules of water for every molecule of gas burned. In an 80% AFUE furnace the exit gases are hot enough to keep this water in the gaseous state until released into the atmosphere from a conventional chimney. I'll bet that you have a 90+% furnace. I'll also bet that you installed it yourself. Now you know why the manufacturer stated that you had to run the 2 inch PVC exhaust stack out of a side wall.

You need to properly vent this unit according to the manufacturer's instructions.
 
  #5  
Old 01-31-07, 11:39 AM
B
Member
Thread Starter
Join Date: Jun 2006
Posts: 27
Likes: 0
Received 0 Likes on 0 Posts
Didn't install it myself. But the family that lived here had lots of people in various trades. So I wouldn't be surprised. So your suggestion is that direct/power vent will solve my troubles? I'll give it a try.

Thanks,
Bill
 
  #6  
Old 01-31-07, 12:20 PM
Jay11J's Avatar
Member
Join Date: Sep 2001
Location: Rochester, Minnesota
Posts: 18,427
Likes: 0
Received 0 Likes on 0 Posts
You said 2".... That brought up a red flag... Is this white PVC??

If so, this needs to brought all the way to the roof in PVC, or out to the side of the home.
 
  #7  
Old 01-31-07, 07:05 PM
N
Member
Join Date: Jun 2006
Posts: 125
Likes: 0
Received 0 Likes on 0 Posts
never seen a 125000 btu furnace with a 2 inch flue. this has definately been tampered with. You said you had to replace the galvanized flue with PVC!!! another huge problem, if this is an 80% furnace that pvc is gonna melt and your going to be in some serious trouble. i would recommend calling a certified technician out to help you with this issue.
 
  #8  
Old 01-31-07, 09:01 PM
Grady's Avatar
Forum Topic Moderator
Join Date: Jan 2005
Location: Delaware, The First State
Posts: 14,401
Received 38 Likes on 36 Posts
Make & model #

It might help us help you if we had a make & model # of the furnace. If this is indeed a 90+, I agree that 2" is too small & it should either go out the sidewall or all the way up the chimney.
 
  #9  
Old 02-01-07, 07:22 AM
B
Member
Thread Starter
Join Date: Jun 2006
Posts: 27
Likes: 0
Received 0 Likes on 0 Posts
Whoah boys and girls! I really do appreciate the assistance, but I'm surprised there's still debate on this thread. I think furd nailed it when he stated that I need to power vent thru the wall.

I never said there was PVC in exhaust run. Yes it's 90 something efficient. No it has not been tampered with. Yes I've found lots of things in the house not done to code and as I identify them I work on them. But its a good house.

I appreciate all the advice, really I do. If there's anything more than this that you think I've missed I'm still ears.

Thanks,
Bill
 
  #10  
Old 02-01-07, 11:36 AM
Jay11J's Avatar
Member
Join Date: Sep 2001
Location: Rochester, Minnesota
Posts: 18,427
Likes: 0
Received 0 Likes on 0 Posts
True, you never said there was PVC, but you said you replaced it with Plastic. Also, you said 2" from the furnace, that is also a PVC size, I am along with Grady about having a 120k furnace on a 2" exhaust.

Give us the full model number on the furnace and we can see what you got.

90% uses PVC and can be vented out the side or on roof.

80% uses Metal B-vent and MUST go up to the roof top.
 
  #11  
Old 02-01-07, 11:47 AM
B
Member
Thread Starter
Join Date: Jun 2006
Posts: 27
Likes: 0
Received 0 Likes on 0 Posts
I'll accept that offer for help, thanks.

It's an InterCity but branded as "ArcoAire" EnviroPlus 90 RPJII

Model # GUK125A020IN

It's black plastic. ABS. Although I do have PVC adaptor in the works.

Thanks,
Bill
 
  #12  
Old 02-01-07, 04:56 PM
Jay11J's Avatar
Member
Join Date: Sep 2001
Location: Rochester, Minnesota
Posts: 18,427
Likes: 0
Received 0 Likes on 0 Posts
ABS is not used around here, so that's why we say thought you had PVC.

I am not able to find the install manual to see what sizing chart says.. I think Grady is able to get the info.

Since I don't know ABS, I am not sure if you can mix them with PVC or not? Others will have to answer that question.

Also, check your local code if it has to have ABS or PVC is allowed. I think I recall reading something that up in Canada it's code to have ABS. Are from up there?
 
  #13  
Old 02-01-07, 07:08 PM
Grady's Avatar
Forum Topic Moderator
Join Date: Jan 2005
Location: Delaware, The First State
Posts: 14,401
Received 38 Likes on 36 Posts
Vent size

I can't get into ICP's tech site tonight for some reason but I will check with the distributor tomorrow.
 
  #14  
Old 02-01-07, 09:38 PM
B
Member
Thread Starter
Join Date: Jun 2006
Posts: 27
Likes: 0
Received 0 Likes on 0 Posts
I can use PVC on a power vent, no problem. Had that at my last abode. This has what I believe to be a power vent. Not as strong as I'm used to, which is why I readily agreed about not venting to the chimney. I never heard of a power vent to the chimney before. If it weren't for the short run, I wouldn't have any ABS. Just PVC. But it doesn't get anywhere near hot anyway.

Continued thanks,
Bill
 
  #15  
Old 02-02-07, 06:41 PM
Grady's Avatar
Forum Topic Moderator
Join Date: Jan 2005
Location: Delaware, The First State
Posts: 14,401
Received 38 Likes on 36 Posts
Vent size

I did check with the local distributor today & was told this furnace should indeed be vented with 3" PVC (forgot about the ABS).
 
  #16  
Old 02-02-07, 09:38 PM
B
Member
Thread Starter
Join Date: Jun 2006
Posts: 27
Likes: 0
Received 0 Likes on 0 Posts
The stock power vent though has a two inch outlet and the hole for the exhaust pipe in the top panel of the unit is for two inch. Is it supposed to widen after that point? That seems kinda silly. It's too clean looking to have been tampered with IMHO.
 
  #17  
Old 02-03-07, 05:45 AM
Jay11J's Avatar
Member
Join Date: Sep 2001
Location: Rochester, Minnesota
Posts: 18,427
Likes: 0
Received 0 Likes on 0 Posts
Right, just as you get past the furnace and elbow up you put a 2 to 3" reducer and go 3" all the way outside to the side of the house. Make sure you have the intake pointed down outside. and exhaust gooseneck up.
 
  #18  
Old 02-03-07, 09:06 AM
B
Member
Thread Starter
Join Date: Jun 2006
Posts: 27
Likes: 0
Received 0 Likes on 0 Posts
OK, thanks. I would have made the mistake of running 2" pipe. I never heard such, but I assume I should have a slight grade towards the outside as well. If there's no such standard I suppose it can't hurt.
 
  #19  
Old 02-03-07, 11:53 AM
Jay11J's Avatar
Member
Join Date: Sep 2001
Location: Rochester, Minnesota
Posts: 18,427
Likes: 0
Received 0 Likes on 0 Posts
You want the pipe to pitch back towards the furnace, not outside. Should have about 1/4" per foot.
 
  #20  
Old 02-03-07, 12:13 PM
B
Member
Thread Starter
Join Date: Jun 2006
Posts: 27
Likes: 0
Received 0 Likes on 0 Posts
duh... of course, don't know what I was thinking. Thanks.
 
  #21  
Old 02-03-07, 09:33 PM
Grady's Avatar
Forum Topic Moderator
Join Date: Jan 2005
Location: Delaware, The First State
Posts: 14,401
Received 38 Likes on 36 Posts
Vent termination

Not to dispute Jay, but I like to put drainage tees on the intake & exhaust after they go outdoors. Better yet is to use a concentric vent kit.
 
  #22  
Old 02-04-07, 05:34 AM
Jay11J's Avatar
Member
Join Date: Sep 2001
Location: Rochester, Minnesota
Posts: 18,427
Likes: 0
Received 0 Likes on 0 Posts
Grady,

??? You mean put a T on both intake and exhaust on the end of the pipe when it gets outside of the house?

If so, a few things can happen.

-Exhaust vaper has good chance of getting sucked into the intake.
-Exhaust vaper build up along the side of the cold house (You've seen our temps.hehe)
-T on intake has higher chance of getting rain water in.
 
  #23  
Old 02-04-07, 12:12 PM
Grady's Avatar
Forum Topic Moderator
Join Date: Jan 2005
Location: Delaware, The First State
Posts: 14,401
Received 38 Likes on 36 Posts
Drainage Tee

Jay,
Hadn't thought about the vapor on the side of the house thing but I don't see how a tee would cause any more of a problem than an ell. In fact I would think less since there is twice the venting area??? When running two pipes outdoors, I always use drainage tees which are kind of a tee/wye hybrid to prevent rain water from coming in. If installed upside down they become a funnel rather than a drain so proper installation is critical.
Whenever possible, I prefer to use a concentric vent kit but in heavy snow areas they frequently can't be used.
 
  #24  
Old 02-04-07, 03:18 PM
Jay11J's Avatar
Member
Join Date: Sep 2001
Location: Rochester, Minnesota
Posts: 18,427
Likes: 0
Received 0 Likes on 0 Posts
It may be diffrent your way since you know how cold we can get.

I know my aunt and uncle had the T set up, and it was nothing but problems for them, so I removed it and put 90o down on intake, then goose neck up on the exhaust, problem solved.

I now understand by turning the T upside down to advoid the rain. but the exhaust vaper will go both up and down.. the down may travel over into the intake (that what happen to my aunt's.)

I too perfer the vent kit, I have the BAYVENT.
 
  #25  
Old 02-05-07, 06:32 AM
HVAC-EMT's Avatar
Member
Join Date: Dec 2006
Location: The Berkshires
Posts: 165
Likes: 0
Received 0 Likes on 0 Posts
Exclamation condensate!!

I highly reccomend that if you have a condensing furnace/boiler that goes from 2" to 3" with it pitching up to the outside, that you put on the horizontal run a 2x3 bushing into a dandy cleanout tee threads pointing down with a male adapter threaded into it that is bushed down to a barb fitting which should have clear tubing attached to it that is looped to act as a trap that should go into a condensate pump that goes to outdoors, pitching out so that the condensate doesn't freeze at the penetration. It should all be PVC because ABS is not rated for the temperatures that PVC is. The threaded part should have teflon tape on it and is so that if anything did get in there, it can be removed easily without cutting the pipe. Also, CO detectors are highly reccomended because if the exhaust is blocked or finds it's way back into the house, death can occur! The termination and air intake should be protected from rodents & debris. Had a freeze up last week because squirrels stored nuts and seeds in the intake pipe, cutting of the air.
 
 

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