Guest guest Posted October 7, 2004 Report Share Posted October 7, 2004 Laverne Dust collects on both the furnace heat exchanger and the internal parts of the electric motor that drives the circulation blower/fan. When the heat exchanger heats up it gets to temperatures that can easily 'fry' dust, producing a number of partly oxidized hydrocarbons, most of which are suspect as far as health is concerned (many are PAH's). An inefficient electric motor usually has internal parts that get quite hot and they too can 'fry' dust. One of the health reasons for moving to more efficient electric motors is their generally-lower internal surface temperatures. Furnace filters are designed to take out the large bits like hair and lint, not the fine stuff that gets deep into our lungs. If a furnace filter is in place, then the fines will still collect on the hot surfaces. If the filters are upgraded to the newer 'Premium' pleated filters, much less fine dust will get through and fry. A 3M Filtrete filter will let even less through. If we could afford the pressure drop of a HEPA filter operating on the full furnace circulation flow they would let almost nothing through. Jim H. White SSAL Fried Dust > > > What causes the smell of " fried dust " in a house heated with a natural gas > furnace? I assume it is dust that accummulates and is burned on the motor > or something, but what or where is the source of the dust most likely to > be? > > Is it caused from an inadequate air filter on the furnace? > > Thanks for your thoughts, > > LaVerne C. > Calgary, AB > > > > > > > FAIR USE NOTICE: > > This site contains copyrighted material the use of which has not always been specifically authorized by the copyright owner. We are making such material available in our efforts to advance understanding of environmental, political, human rights, economic, democracy, scientific, and social justice issues, etc. We believe this constitutes a 'fair use' of any such copyrighted material as provided for in section 107 of the US Copyright Law. In accordance with Title 17 U.S.C. Section 107, the material on this site is distributed without profit to those who have expressed a prior interest in receiving the included information for research and educational purposes. For more information go to: http://www.law.cornell.edu/uscode/17/107.shtml. If you wish to use copyrighted material from this site for purposes of your own that go beyond 'fair use', you must obtain permission from the copyright owner. > Quote Link to comment Share on other sites More sharing options...
Guest guest Posted October 7, 2004 Report Share Posted October 7, 2004 LaVern, The smell is caused by a thin layer of fine dust that has collected on the airstream side of the metal heat exchanger during the off season. On the very first startup of the heating season, that layer of fine duct gets a bit " cooked " for lack of a better term. Some smell is to be expected since A/C filters do not block all fine dust and particles. If the first cycle smell if really strong (or persists for many cycles thereafter) or it sets off the smoke detectors in the dwelling, then you can pretty much bet there is an air filtration problem with the system. Best Regards, Phil S. Fried Dust > > > What causes the smell of " fried dust " in a house heated with a natural gas > furnace? I assume it is dust that accummulates and is burned on the motor > or something, but what or where is the source of the dust most likely to > be? > > Is it caused from an inadequate air filter on the furnace? > > Thanks for your thoughts, > > LaVerne C. > Calgary, AB > > > > > > > FAIR USE NOTICE: > > This site contains copyrighted material the use of which has not always > been specifically authorized by the copyright owner. We are making such > material available in our efforts to advance understanding of > environmental, political, human rights, economic, democracy, scientific, > and social justice issues, etc. We believe this constitutes a 'fair use' > of any such copyrighted material as provided for in section 107 of the US > Copyright Law. In accordance with Title 17 U.S.C. Section 107, the > material on this site is distributed without profit to those who have > expressed a prior interest in receiving the included information for > research and educational purposes. For more information go to: > http://www.law.cornell.edu/uscode/17/107.shtml. If you wish to use > copyrighted material from this site for purposes of your own that go > beyond 'fair use', you must obtain permission from the copyright owner. > Quote Link to comment Share on other sites More sharing options...
Guest guest Posted October 8, 2004 Report Share Posted October 8, 2004 Jim: Another factor may be that many furnace motors are " air over " meaning that they use the circulating air in the duct to cool the motor. TENV or TEFC motors would be more expensive but are totally-enclosed (totally-enclosed non-ventilated or totally-enclosed fan-cooled). Don Schaezler, Ph.D., P.E., CIH ETC Information Services, LLC Cibolo, Texas Jim H. White wrote: >Laverne >Dust collects on both the furnace heat exchanger and the internal parts of >the electric motor that drives the circulation blower/fan. When the heat >exchanger heats up it gets to temperatures that can easily 'fry' dust, >producing a number of partly oxidized hydrocarbons, most of which are >suspect as far as health is concerned (many are PAH's). An inefficient >electric motor usually has internal parts that get quite hot and they too >can 'fry' dust. One of the health reasons for moving to more efficient >electric motors is their generally-lower internal surface temperatures. > >Furnace filters are designed to take out the large bits like hair and lint, >not the fine stuff that gets deep into our lungs. If a furnace filter is in >place, then the fines will still collect on the hot surfaces. If the filters >are upgraded to the newer 'Premium' pleated filters, much less fine dust >will get through and fry. A 3M Filtrete filter will let even less through. >If we could afford the pressure drop of a HEPA filter operating on the full >furnace circulation flow they would let almost nothing through. >Jim H. White SSAL > > Fried Dust > > > > >>What causes the smell of " fried dust " in a house heated with a natural gas >>furnace? I assume it is dust that accummulates and is burned on the motor >>or something, but what or where is the source of the dust most likely to >>be? >> >>Is it caused from an inadequate air filter on the furnace? >> >>Thanks for your thoughts, >> >>LaVerne C. >>Calgary, AB >> >> >> Quote Link to comment Share on other sites More sharing options...
Guest guest Posted October 8, 2004 Report Share Posted October 8, 2004 Unless the blower motor is malfunctioning in some manner that is causing it to overheat, the amount of heat generated by the motor is negligible in comparison to the that of the heat exchanger when the burners are in operation. The blower motor's role in the first-firing smell of the heating unit is meaningless in comparison. Try turning the blower to the 'ON' position before you actually fire up the furnace and see how much burning odor you get from the system. Even after you have allowed the motor to run for some time and come up to its normal operating temperature, there will be no smell. Now turn the blower off and fire up the furnace burner. When that blower starts now, there will be no comparison between those two odor events. Now here's something you should ABSOLUTELY NOT do but is offered here just as a mental exercise. While the furnace is in full operation after coming up to normal operating temperature, kill the power to the unit and shut it all down. Open the blower compartment and an inspection hole at the furnace heat exchanger. Touch the blower motor and see just how hot it isn't. It may be warm, or even VERY warm, but it will not be so hot that you can not hold your hand on it for a long 5 count (unless the motor is malfunctioning). Now go to your inspection port and put your hand on the airstream side surface of the heat exchanger. You will not be able to take your hand off of it fast enough to keep from blistering in all likelihood. The only times I have ever smelled a burning odor from a blower motor was when that motor was malfunctioning and overheating at the limit of its internal overload or when its windings were literally burned due to grounding or an electrical short. Phil (30 yrs in the HVAC business) S. Fried Dust >> >> >> >> >>>What causes the smell of " fried dust " in a house heated with a natural >>>gas >>>furnace? I assume it is dust that accummulates and is burned on the motor >>>or something, but what or where is the source of the dust most likely to >>>be? >>> >>>Is it caused from an inadequate air filter on the furnace? >>> >>>Thanks for your thoughts, >>> >>>LaVerne C. >>>Calgary, AB >>> >>> >>> > > > > > > > > > FAIR USE NOTICE: > > This site contains copyrighted material the use of which has not always > been specifically authorized by the copyright owner. We are making such > material available in our efforts to advance understanding of > environmental, political, human rights, economic, democracy, scientific, > and social justice issues, etc. We believe this constitutes a 'fair use' > of any such copyrighted material as provided for in section 107 of the US > Copyright Law. In accordance with Title 17 U.S.C. Section 107, the > material on this site is distributed without profit to those who have > expressed a prior interest in receiving the included information for > research and educational purposes. For more information go to: > http://www.law.cornell.edu/uscode/17/107.shtml. If you wish to use > copyrighted material from this site for purposes of your own that go > beyond 'fair use', you must obtain permission from the copyright owner. > Quote Link to comment Share on other sites More sharing options...
Guest guest Posted October 8, 2004 Report Share Posted October 8, 2004 Phil Internal surface temperatures on some of the cheaper motors used in furnaces in tract (or just minimum first cost) houses do get very hot indeed. The outside of the motor does not. If you were to read the protocol for determining the horsepower of a motor you would see that there are several motor monitoring points and there is a huge difference in the temperatures on the surface of the windings on the inefficient motors compared to the outside of the casing. As motors become more efficient this difference drops off dramatically. There were some really crappy motors used out there for a while. Another point; once the temperature gets high enough to 'fry' dust, it does not matter if it gets higher, as is the case of the heat exchanger. By the way, the energy efficiency of motor-driven things is the way I make most of my living, so I too am an expert, but as a researcher/scientist. I also have over 40 years of experience in this area, so I outrank you if this is one of those 'who is the biggest ***** in the schoolyard' sorts of things. Jim H. White Formerly Senior Advisor - Building Science, Canada Mortgage and Housing Corporation (home of the best studies on why houses make people sick) Now jus President of a small company called System Science Associates Ltd. (SSAL) Fried Dust > >> > >> > >> > >> > >>>What causes the smell of " fried dust " in a house heated with a natural > >>>gas > >>>furnace? I assume it is dust that accummulates and is burned on the motor > >>>or something, but what or where is the source of the dust most likely to > >>>be? > >>> > >>>Is it caused from an inadequate air filter on the furnace? > >>> > >>>Thanks for your thoughts, > >>> > >>>LaVerne C. > >>>Calgary, AB > >>> > >>> > >>> > > > > > > > > > > > > > > > > > > FAIR USE NOTICE: > > > > This site contains copyrighted material the use of which has not always > > been specifically authorized by the copyright owner. We are making such > > material available in our efforts to advance understanding of > > environmental, political, human rights, economic, democracy, scientific, > > and social justice issues, etc. We believe this constitutes a 'fair use' > > of any such copyrighted material as provided for in section 107 of the US > > Copyright Law. In accordance with Title 17 U.S.C. Section 107, the > > material on this site is distributed without profit to those who have > > expressed a prior interest in receiving the included information for > > research and educational purposes. For more information go to: > > http://www.law.cornell.edu/uscode/17/107.shtml. If you wish to use > > copyrighted material from this site for purposes of your own that go > > beyond 'fair use', you must obtain permission from the copyright owner. > > Quote Link to comment Share on other sites More sharing options...
Guest guest Posted October 9, 2004 Report Share Posted October 9, 2004 Jim, I don't want to turn this into an argument by any stretch of the imagination and I certainly respect your knowledge and experience. I only signed off with " 30 yrs in the HVAC business " because no one here in this forum knows me from Adam and I wanted to follow my (publicly expressed) opinion with some reason for others here to at least give it the modicum of consideration it deserves. My previous post was certainly not meant as a proclamation that I was the " ...biggest ***** in the schoolyard'. I would however like to add one more point to my original comments regarding this topic. The blower motor on a forced air heating system (in my part of the country at least) is used year round because that same blower motor is utilized for air movement during the cooling season. That means that when some portion of the motor's exposed internal parts do get hot enough to fry the dust, such dust will be fried as it tries to accumulate during blower operation. Because of this, dust in the motor never really gets the opportunity to build up in any significant quantity on those hot spots you talked about. Its kind of a " pay/fry as you go " in regard to any dust that might contact those areas. The heat exchanger on the other hand banks it entire load of accumulated dust all during the cooling season and waits to fry it all off in mass at the first fire up of the heating season. That is the smell from the furnace we are all familiar with and that is why I say that the blower motor's contribution to that smell is negligible if not nonexistent. The only notable frying dust odor I have ever smelled from a blower motor in operation was when the motor was failing and overheating. That's when all of the accumulated dust on those parts of the motor that don't normally get very hot start to fry. Phil S. Fried Dust >> >> >> >> >> >> >> >> >> >>>What causes the smell of " fried dust " in a house heated with a natural >> >>>gas >> >>>furnace? I assume it is dust that accummulates and is burned on the > motor >> >>>or something, but what or where is the source of the dust most likely > to >> >>>be? >> >>> >> >>>Is it caused from an inadequate air filter on the furnace? >> >>> >> >>>Thanks for your thoughts, >> >>> >> >>>LaVerne C. >> >>>Calgary, AB >> >>> >> >>> >> >>> >> > >> > >> > >> > >> > >> > >> > >> > >> > FAIR USE NOTICE: >> > >> > This site contains copyrighted material the use of which has not always >> > been specifically authorized by the copyright owner. We are making such >> > material available in our efforts to advance understanding of >> > environmental, political, human rights, economic, democracy, >> > scientific, >> > and social justice issues, etc. We believe this constitutes a 'fair >> > use' >> > of any such copyrighted material as provided for in section 107 of the > US >> > Copyright Law. In accordance with Title 17 U.S.C. Section 107, the >> > material on this site is distributed without profit to those who have >> > expressed a prior interest in receiving the included information for >> > research and educational purposes. For more information go to: >> > http://www.law.cornell.edu/uscode/17/107.shtml. If you wish to use >> > copyrighted material from this site for purposes of your own that go >> > beyond 'fair use', you must obtain permission from the copyright owner. >> > Quote Link to comment Share on other sites More sharing options...
Guest guest Posted October 10, 2004 Report Share Posted October 10, 2004 Phil One of the advantages of running a circulation blower year round is that you do spread out any frying on the motor, if it occurs. The second advantage is that, after looking at your electrical bill, you may decide to go for one of the much more efficient motors next time around. When we in Canada funded a survey of the actual consumption of circulation blower motors versus the flow power that they delivered (in SI simply ([L/s]/1000)*Pa = Watts of flow power), we found that normal furnaces were between 5 and 20% efficient (although few were over 15%) at turning electrical power into flow power (which is what we really want & need). At 10% subsystem efficiency, 90% of the purchased electricity is turned into heat in the motor/fan combination, to be used as household heat during the heating season, but this heat becomes a significant part of the cooling load in other parts of the year when air conditioning is needed. Some of the new GE ECM motors, driving intelligently-selected fans, were running at close to 25%, for a significant reduction of 5:1 compared to the 5% efficient ones. It should be possible to make the set closer to 40% efficient, if the demand was there for better efficiency, but it is a system problem that is not being well researched, even with the research that is going on. Oh Well! Peace be with you and thanks for your response. Jim H. White SSAL Fried Dust > >> >> > >> >> > >> >> > >> >> > >> >>>What causes the smell of " fried dust " in a house heated with a natural > >> >>>gas > >> >>>furnace? I assume it is dust that accummulates and is burned on the > > motor > >> >>>or something, but what or where is the source of the dust most likely > > to > >> >>>be? > >> >>> > >> >>>Is it caused from an inadequate air filter on the furnace? > >> >>> > >> >>>Thanks for your thoughts, > >> >>> > >> >>>LaVerne C. > >> >>>Calgary, AB > >> >>> > >> >>> > >> >>> > >> > > >> > > >> > > >> > > >> > > >> > > >> > > >> > > >> > FAIR USE NOTICE: > >> > > >> > This site contains copyrighted material the use of which has not always > >> > been specifically authorized by the copyright owner. We are making such > >> > material available in our efforts to advance understanding of > >> > environmental, political, human rights, economic, democracy, > >> > scientific, > >> > and social justice issues, etc. We believe this constitutes a 'fair > >> > use' > >> > of any such copyrighted material as provided for in section 107 of the > > US > >> > Copyright Law. In accordance with Title 17 U.S.C. Section 107, the > >> > material on this site is distributed without profit to those who have > >> > expressed a prior interest in receiving the included information for > >> > research and educational purposes. For more information go to: > >> > http://www.law.cornell.edu/uscode/17/107.shtml. If you wish to use > >> > copyrighted material from this site for purposes of your own that go > >> > beyond 'fair use', you must obtain permission from the copyright owner. > >> > Quote Link to comment Share on other sites More sharing options...
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