When I Turn My River North Furnace on I Smell a Strange Odor but It Goes Away After Awhile

I was working in a very nice condo for the first time, in the River North area of Chicago, and after examining the furnace I asked the homeowner if they smelled anything funny when they first turned the furnace on this year.  They answered “Yes, we smell the same thing every year for a little while when we first turn the heat on”.

The following is for informational use only and is not intended as a “How to Guide”.  Gremillion Mechanical always recommends that if there is a problem with any complex appliance in your home to call a professional service technician trained in the repair of that equipment.  Remember to always “stay in your comfort zone” when trying to perform any task related to your furnace and if you feel unsafe, call for professional help!

A very common thing to have happen in furnaces without air conditioning is that after a long period of sitting idle and not being used they can have some dust build up on the heat exchanger inside the unit.  This dust can be on the combustion side as well as the air side.  In this type of situation, it would be normal for the dust to have to burn off the heat exchanger and therefore causing an odor that is not familiar to most people.  This odor seems to go away quickly but more likely is the fact the everyone gets used to odors quickly and they just ignore the odor.

Another cause could be the odor of flue gas in the air stream.  The furnace contains a “heat exchanger” that heats up to allow for forced air heating, but seals and separates the combustion chambers from the sir flowing into your home.  The air in your home flows around the outside of the heat exchanger while gas burners heat the inside.  One by-product of the combustion of natural gas is a mixture of gases that need to be vented to the outside.  Since the heat exchanger is made of metal, it is prone to corrosion caused by the combustion process gasses that are corrosive to metal.  Over time, this corrosive action can cause holes in the heat exchanger, usually around welds.  This can allow flue gas to escape from the combustion chamber into the airstream that enters your home.  The carbon monoxide that is in the flue gas may now be entering your home.  The carbon monoxide gas is odorless in of itself, but other gases mixed in with the CO (Carbon Monoxide) may have an odor.

Orange flame is a bad sign

This is an actual furnace that Gremillion Mechanical was called to do a clean & check on.  The left center of the picture shows that the center burner is burning orange.  This could be caused by several different issues but the furnace pictured here has holes in the heat exchanger.  This of course is not a good situation for anyone, this furnace needed to be replaced and would have to be shut off by Gremillion Mechanical and of course the owner told that the unit would have to be replaced.  Any reputable mechanical contractor would not allow the unit to run even if it was the only heat source in the home.  You and your family may be cold, but the flue gases being introduced into the airstream that serves your home can make your family very, very ill.  We are not the “Heating Police”, as one client called us, and the homeowner has the right to make his own decision about the safety of their family.  The technicians that work for Gremillion Mechanical will not allow this furnace to run while we are on site, but again the homeowner has the right to turn his equipment on if they choose.

Rusting of the heat exchanger end plate

This picture shows a closer view of the end plate of the heat exchanger of the unit shown above.  It is easy to see that this plate is rusting, but it looks like it doesn’t have any holes in it that would cause any problems.  Looks can be very deceiving to the untrained eye, and also very dangerous to the occupants of the space that is served by a unit in this condition.

Complete failure of the combustion chamber

This photo is of the air side of the heat exchanger in the same unit as above.  You can easily see the rust around the connection point, and separation of where the heat exchanger chambers are connected to the heat exchanger end plate.  This is why the flame is burning orange in the first picture.  This condition not only allows dangerous gases into your home, but also can be a fire hazard starting a fire inside the furnace and possibly the home.  Again, this is a very dangerous condition and the technicians at Gremillion Mechanical would not leave this furnace operating.

We understand that times are tough for a lot of people and replacing your furnace is probably the last many of us need to hear.  The unit used in this article was replaced by the homeowner, but could have this furnace been fixed?  The answer is yes but at a higher cost then replacing the entire unit.  Plus, replacing the unit comes with manufacturer warranty that will cover most parts for up to 10 years (not all manufacturers offer 10 year warranties).

Chicago Heating Repair
3526 S. Paulina St. ChicagoIL60609 USA 
 • 773-234-4575

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