Air In Pvc Pipe For Gas Furnace Froze


  #1  
Old 01-20-03, 06:35 AM
BITT
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Unhappy Air In Pvc Pipe For Gas Furnace Froze

I HAVE A 3 MONTH OLD AMERICAN STANDARD 92% EFFIC 120K BTU GAS FURNACE(SORRY DONT HAVE MODEL #). BOTH THE EXHAUST PVC PIPE & THE PVC PIPE FOR THE FRESH AIR VENT OUT THE SIDE OF THE HOUSE. THE FURNACE WAS INSTALLED BY AN AUTHORIZED INSTALLER & HE DID PULL A PERMIT SO THE TOWN INSPECTED IT. ANY WAY THE PROBLEM IS THIS: THIS PAST SAT NIGHT THE TEMP DROPPED BELOW ZERO & THE FURNACE WASN'T WORKING. LUCKILY I FOUND THE PROBLEM, THE PVC PIPE BRINING IN FRESH AIR WAS BLOCKED WITH SNOW/ICE AT THE OPENING. THE PIPE SEEMS TO BE INSTALLED CORRECTLY IT IS ANGLED SLIGHTLY DOWN TO THE GROUND & IT DOES HAVE A CAP SO THAT IT CAN ONLY SUCK IN AIR FROM BELOW SO WATER OR SNOW CAN NOT DRIP INTO IT. THE PIPE IS ABOUT 5 1/2 FT ABOVE THE GROUND & WE HAVE HAD PLENTY OF COLD NIGHTS BEFORE WITHOUT THIS HAPPENING. HAVE YOU EVER HEARD OF THIS HAPPENING BEFORE? I KNOW THE EXHAUST PIPE TENDS TO HAVE MOISTURE IN IT BUT HOW WOULD THE AIR INLET PIPE GET MOISTURE/SNOW/ICE IN IT? ANY SUGGSTIONS HELPING ME PREVENT THIS IN THE FUTURE WOULD BE GREATLY APPRECIATED THE TEMPS ARE EXPECTED AT OR BELOW ZERO EVERY NIGHT THIS WEEK AND MY WIFE IS 6 MOS PREGNANT. I HAVE CALLED THE INSTALLER WHO IS UNDER CONTRACT TO SERVICE IT FOR A YEAR UNDER THE MANUFACTER'S WARRANTY SEVERAL TIMES BUT HE HASN'T CALLED BACK!
 
  #2  
Old 01-20-03, 11:10 AM
brickeyee
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This sounds like a not very funny prank someone pulled. Snow does not fall up. I have been leery of having important things like air intakes and flue exhausts within reach from the ground for a long time. Spend a night up late and watch.
And please turn off the caps. On boards like this that is the equivalent of shouting.
 
  #3  
Old 01-21-03, 05:51 AM
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BITT:

The furnace mfr has a specific distance that the intake and exhaust are to be spaced apart.

Could the exhaust be drawn up the intake?
 
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Old 01-24-03, 05:14 AM
BITT
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Thanks Greg! I did finally get in touch with my furnace installer and he said he will make sure the two pipes are far enough apart. I did turn the heat up to 85 last night when the outside temp was around 5 and let the furnace run for aprox 2 hrs. There was ice forming inside the inlet pipe so it sounds like you may be right. Is there anything I can do other than having the pipes moved? I am trying to avoide having more holes drilled into the side of my house.
 
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Old 01-24-03, 05:58 AM
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BITT:

I'm not sure if the intake pipe can have an elbow installed to extend it further along the house. You would have to consult the mfr's literature.

It may be preferable to have a new hole made though, your pipe would not be exposed to outside damage that way.
 
  #6  
Old 01-24-03, 10:04 AM
Cinci1
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Unhappy Same Problem

I'm having the same problem. I have a TempStar furnace, but I definitely believe it's a problem involving the exhaust being pulled into the intake and the condensation freezing. When I purchased the house, the previous owner or installer had added a pipe to the intake, extending it about five feet away. Unbelievably, the pipe actually slants upward! So, when it gets really cold (these 0 degree nights have got to go!), the pipe still freezes over. I have not had a chance to fix the situation yet, but guess what I'll be doing this weekend?!?
 
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Old 01-24-03, 10:06 AM
Cinci1
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FollowUp Question

One other question. Would it be of any use to put any type of pipe wrap or insulation around the intake pipe? Obviously I need to fix the angle on the pipe, but I want to ensure that this doesn't happen again (2:30 in the morning at 0 degrees is not when I like to be under my deck with a coat hanger!).

Thanks!
 
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Old 01-24-03, 10:53 AM
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It would not be a good idea to insulate the intake pipe as you may only cause a problem somewhere else.

You would have to keep in mind that being too close together is only one possible cause of your problem.

It could be that moist air is somehow being discharged through the intake. Maybe when the furnace is not running.

See if you can detect a slight discharge of air when the furnace is not running.
 
  #9  
Old 01-24-03, 11:05 AM
BITT
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Thanks for all the info Greg. You have helped a great deal. I am almost positive at this point that the intake is sucking in the moist exhaust air. The pipe only freezes where it is open to the elements and has only happened when it is extremely cold with the furnace runnning for long periods of time. I think at this point the only thing I can do is to have the intake pipe moved over.
 
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Old 01-24-03, 04:53 PM
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By the way.

How far apart are the two pipes?
 
  #11  
Old 01-24-03, 08:29 PM
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Cinci..... did you say

(2:30 in the morning at 0 degrees is not when I like to be under my deck with a coat hanger!).

Are you saying that they have the furance piped under your deck!?! If so, that's why your havig problem!

With the mositer being trapped under your deck, it WILL get sucked back into your intake pipe.

I'd move those pipe to an open side of the house, not under the deck.. how long has the been there? If this a recent project, I'd call the installer back to fix it.
 
  #12  
Old 01-27-03, 07:31 AM
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Done over 5 years ago

Unfortunately, it was like this when we bought the house 4 years ago. What I'm guessing happened was that the initial installation happened before the deck was put on. When the deck was put on, they must have known a problem would occur, so they ran an extension on the intake pipe about 4 ft away from the exhaust. Would have been a great idea, except that the extension pipe gradually got higher, causing any condensation to collect in the joint. The good news is that I finally got around to lowering the extension, and (knock on wood), it's been working fine since (got down to -5 last night, and the heat's still going!). One last question though, does extending the intake pipe create any additional strain on the furnace (since it's pulling the intake air farther?). I'm really not looking to have a new intake pipe put in, but if it's killing my furnace, I'd have to think about it.

Thanks for an AWESOME site, and all the helpfull info.!
 
  #13  
Old 12-07-10, 06:35 AM
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There are maximum distances the pipe may be extended (especially once it is reduced and exits the house). You need to follow the manufacturer recommendation. It is not a good idea to ignore the separation distances recommended between exhaust and intake. The furnace is very pressure difference sensitive. My furnace recommends if the intake extends more than 24" outside the house that it be insulated.
 
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Old 12-07-10, 02:09 PM
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Hopefully the OP has solved his problem in the seven years since he posed his question.
 
 

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