exhaust smell in house

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Old 02-12-05, 06:55 PM
Ismellsomething
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Question exhaust smell in house

I hope I am doing this right...It is my first post on this board and I don't know how else to start but to jump in...We moved in November 2004 to a house with an older oil-fired forced hot air system. We have a pronounced smell on the second floor that we describe as an "exhaust" smell. Furnace guys don't think it smells like combustion fumes but can't describe the smell either. It is only noticible when the furnace kicks on but BEFORE the fan starts blowing. There is a slight current through the air vents when the furnace is off, a little greater when furnace is on, and naturally, most current with blower on. Is it normal that air flows through the vents when furnace is off? No soot on walls, vents, ceilings, etc. One service man said that we were having delayed ignition, but why would we smell it upstairs and not in basement, unless the heat echanger was cracked? And why only smelling on top floor? First floor and basement area (which does have a heat vent and a return) smell fine. Had the ducts cleaned by Sears about a month ago. System has an electronic filter and a humidifier which we've not turned on this winter, since it is probably gunked up. Any help would be greatly appreciated!
 
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Old 02-13-05, 06:10 AM
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It does sound like a crack in the heat exchanger. Most can be seen with a mirror and a light. Some are on top of the furnace from humidifiers that malfunctioned years ago and must be viewed from the top. The first test would be the draft test over the fire with blower off, then on. It has to be done carefully but it will indicate even a small leak. Second would be a smoke candle. It is easy to light and throw in, but the inspection has to be done quickly (relatively). I also have heard of a test requiring oil of wintergreen on a bunch of cotton balls but I have never tried that one. I have had a few furnaces that I could not pinpoint the source of the leak but when I pulled them out and took them apart, I found rusted seams and cracks that were hidden from view. Another test I now use is to start the burner and put a digital combustion tester in the flue pipe. See what the CO2 level is and as soon as th eblower comes on, if the CO2 drops off, there is a leak in the heat exchanger. It is a reliable test but again does not pinpoint the leak. Your electronic air cleaner would not help you because the odor isn't coming back the return, it is being generated in the furnace and sent out the supply duct. Keep us informed on your progress.


Ken
 
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Old 02-13-05, 11:52 AM
Ismellsomething
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Thanks for your reply. We've heard that a cracked heat exchanger would cause black marks on walls, around pictures, on TV screens, etc. We just had the whole house painted fresh before we moved in (Nov 2004) and there's no sign of any soot. Would that be because it is too soon after painting, or that heat exchanger cracks can exist without soot? Any thoughts on why the smell is only on the second floor?
 
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Old 02-13-05, 12:23 PM
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Before the blower comes on, the tallest ducts create the most convection. Those are the ones on the second floor. The reason you don't smell it when the blower comes on is because there is 100 times more airflow and it pressurizes the heat exchanger with air from the blower. That reverses the direction of leakage and then house air is being driven into the combustion air. If your burner is burning efficiently, there isn't going to be soot by the bucket, but it will eventually stain the walls just like you see outside of himes with power vented oil burners. It takes a few years for the stains to show up but they will eventually need to be washed off the siding. It is just a fact of life with the outside but it is not something you want to have inside.

Ken
 
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Old 02-13-05, 12:24 PM
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Id say it takes time to get the wall black from the smoke. You also can get a smoke bomb that you put in the furnace after you run it for a time and get it hot then put it in . One brand is called Smokeys.If it is cracked the smoke will get in the home but dont hurt anything. Id say the smell is on the second floor cause the duct there will act like a flue up to it with the blower off. On that EAC filter there Id go over to a good pleated kind . Will do a much better job. I find people just dont keep them clean like they should and then they dont work and do the job they should.


ED
 
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Old 02-13-05, 01:01 PM
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A couple of other possibilities are a bad chimney & a downdraft. In the case of the chimney, particularly if this is an old house, there could be cracks in the chimney allowing exhaust fumes into the house. With a downdraft, sometimes the exhaust will exit the chimney then come down the roof. With a downdraft, it usually goes away as the chimney warms creating more draft up the chimney. A complete combustion analysis is certainly in order.
 
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Old 02-13-05, 02:13 PM
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Thanks, everyone. We're going to get the oil company guy over again, and this time, we think we'll be able to actually get him to smell it...it took us a while to realize it was only on the second floor, furnace running, blower off. Then it sounds like a smoke test or combustion analysis is a good idea. We're not opposed to changing the furnace, but then again, if the chimney is the problem, then I guess that won't help much. If the smoke test doesn't show anything, would it be a good idea to get the chimney lined with stainless and see what that does? Don't want to worsen the updraft by creating a smaller flue...I've thought of having the chimney video-inspected to check for leaks/cracks, too. But, not sure if that would be good money spent. Will let you know what happens this week. Thanks again.
 
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Old 02-13-05, 02:22 PM
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I would hold off on the chimney until after the service guy does his thing. Believe or not, a chimney too large is as much or more of a problem than one too small. Most if not all professional chimney sweeps can do a good job of inspecting the chimney. If you are seriously considering a new furnace, Thermo-Pride makes the finest oil fired furnaces out there. Just be prepared, you get what you pay for. They are not made cheaply & don't sell for cheap.
 
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Old 02-13-05, 04:10 PM
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I agree with Grady. Don't spend much time or money trying to blame the chimney. There is almost always a negative pressure in there and there isn't much of a chance that something would come out between the top and bottom and if it did, it wouldn't travel around the house. Make sure they check that furnace carefully.

Ken
 
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Old 02-14-05, 05:55 AM
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Don't spend any time trying to figure this out on your own. Get a pro in there and have them go through this thing before it gets to the point that you don't wake up.

Call in a hvac company, you will more than likely get better results than from the oil company.
 
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Old 02-16-05, 12:51 PM
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Originally Posted by mattison
Call in a hvac company, you will more than likely get better results than from the oil company.
I have been servicing oil heat equipment for over 25 years in a family business that my father started over 40 years ago. I do alot of work for oil companies and our own customers. Most HVAC companies do mostly gas heat. I consider myself a professional. There are many fine techs out there that work for oil companies. Its like any trade there are good and bad everywhere.
 
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Old 02-17-05, 04:48 AM
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Al is totally correct about the techs who do work for oil companies and I appologize for my statement if I offended any oil guys.

Maybe you should call your oil company and speak to the service manager and explain that you are concerned that there may be co in your home and would they send out a seasoned tech to check the levels and inspect the furnace. With the test equipment available to us today he does not have to rely on just his nose.
 
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Old 02-17-05, 08:25 AM
Ismellsomething
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follow up--blower motor test

The oil company sent someone two days ago to check out the smell. We had painting done that day and all he could smell was paint, although I got the "smell". He said he'd send someone to do a smoke test. A seasoned oil service man (35+ yrs in the business) arrived today to do it. Turned out that he couldn't put the bomb in the chamber because of its design, but he did another test instead. He opened the chamber door with the blower off and observed the flame, positioning his hand in front of the opening. He then turned the blower motor on and could no longer keep his hand in front of the door from the heat being pushed out. I saw the flames change direction each time he switched the blower on and off. He said this test meant it was obvious that there was a hole, since the fan should not impact the combustion chamber. Sounds like what KField was saying, but is this test conclusive? Makes sense, but other than a smell that no one can agree on, there are no other symptoms.

The HVAC company that we know in our area only services commercial sites, so we are still looking for an HVAC specialist, but maybe given today's info we've determined with certainty that we need a new furnace...interested in your opinions

Thanks.
 
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Old 02-17-05, 08:48 AM
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Turned out that he couldn't put the bomb in the chamber because of its design,
Dont know why it didnt fit . But he new how to go and find it. It pays to get a good tech. Glad you got it Now get a new furnace get 3 bids. Id say what does that last tech sell might pay to get one from him are who he said to call.

ED
 
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Old 02-17-05, 10:09 AM
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I can't believe thet the first tech on the job didn't find that. Sometimes the draft over the fire will change ever so slightly when the blower starts and you need to be careful with the placement of the draft gauge. But in your case, there is enough of a hole in the heat exchanger to burn the hair off of a techs knuckles. If the furnace was serviced and adjusted with combustion testing equipment, the defect would have shown up as soon as the blower started. Check for a company to install the new one who will know how to maintain and troubleshoot it too.

Ken
 
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Old 02-17-05, 12:53 PM
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The hand infront of the door test will usually only work on large cracks or holes in the heat exchanger. You now know you need a new furnace. You want a good one. Something like a Hallmark or Thermopride. IMHO they are the only two worth installing
 
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