Sour Smell when Air Conditioner on

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Sour Smell when Air Conditioner on

Postby perquanion » Mon Jun 27, 2005 3:12 pm

What can cause a sour smell when the central air conditioner is running? This is a new house and when it ran a week ago it didn't smell. but this time when it was turned on the smell was there.
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Postby HollowPoint69 » Mon Jun 27, 2005 3:22 pm

Mold?
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Postby DAVE1 » Mon Jun 27, 2005 3:24 pm

could be something in the vents and is stinking up your hole house
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Postby nascarfool.com » Mon Jun 27, 2005 3:28 pm

It could be just about anything. (1) The inside of the furnace is insulated, if any water leaks on to the insulation it will cause a nasty smell. (2) Do you have an electronic air cleaner ? If so, it could be set for the wrong CFM (air flow). I have found many of them set to the highest CFM. When set wrong, the electronic air cleaner will create "ozone". It can be a very nasty odor. (3) Stuff in the duct work. I have pulled many items out of the duct work. Ranging from sawdust, dead critters and human waste. (4) The air conditioner removes moisture from the air. I suspect this could be your problem. The indoor coil drain pan is not designed to completely drain. Therefore you could have stale water sitting in the drain pan. When the blower motor comes on it will send the odor up through the ducts. If the house and system are new, check into getting it looked at under warranty. The systems I install come with a two year labor/ 10 year parts warranty.
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Postby Karlsweldt » Tue Jun 28, 2005 6:56 am

nascarfool.com's advice should be taken. The "coil" which sits in the air chamber above a furnace or "air handler" unit can leave water levels in the tray, which bacteria love! Mold forms, and the spores are blown about the dwelling. If possible, have the unit attended to by the landlord or premises owner under warranty. Otherwise, call in a contractor specialized in "sanitizing" A/C systems. You might try spraying a 10% bleach solution into the chamber, while the unit is off.. and allowing it to remain unused for a day. Then spray distilled water into the chamber, to rinse the solution. But it may not be totally effective. Disassembly and service on those units should be done only by qualified personnel. If a refrigerant line is ruptured, there are serious frost-bite and other dangers present.. you may suffocate from the displacement of oxygen by the refrigerant gases! Never, ever smoke or have an open flame in the area, when refrigerant gases may be present!!! Attend to the remedial action now, before serious bronchial trauma results.
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Postby trexntx » Tue Jun 28, 2005 8:10 am

Any hamsters missing? :wink:
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Postby Tolemac » Tue Jun 28, 2005 11:54 am

Damn. Just read nascarfool's post and thought he must be a HVAC guy, then I remembered he IS, so listen to him and you'll be right. 8)
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Postby c327 » Tue Jun 28, 2005 4:24 pm

Dirty underware under the bed he he he.

No really now. Probably for the same reason auto ac smells after it was turned off and left that way for a while then turned back on.

Probably the drain holes or piping in the evaporator are clogged and not draining completely. What you are smelling is stale water that is left in the evaporator after it has shut down and not drained all the way. If the AC system is a year or older the evaporator could be dirty and needs to be washed out.
If it's a house AC there should be a pan under the evaporator, the pan should have two drain pipes, one low level and one safety for high level. This pan should also be cleaned once in a while.
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Postby nascarfool.com » Tue Jun 28, 2005 5:44 pm

c327 wrote:Probably the drain holes or piping in the evaporator are clogged and not draining completely. What you are smelling is stale water that is left in the evaporator after it has shut down and not drained all the way. If the AC system is a year or older the evaporator could be dirty and needs to be washed out.
If it's a house AC there should be a pan under the evaporator, the pan should have two drain pipes, one low level and one safety for high level. This pan should also be cleaned once in a while.


14 years as an HVAC tech and the only time I've had to clean a coil is when the owner or renter was too lazy to keep an air filter in the system. If you change your filter on a regular basis, you will never have to have the A-coil cleaned (evap coil). Where I live, only one city requires the use of both drains from the A-coil. The low drain is piped to the floor drain or condensate pump and the high drain is piped one foot above the floor next to the furnace (if installed in a basement. Attics and crawl space installs are piped differently). The purpose of the secondary drain is to let you know when the primary line is plugged. The A-coil in an upflow configuration is designed to allow water to remain in the pan. That water is there to create a liquid seal between the bottom of the coil and the pan to prevent the air from going around the coil rather than through the coil.

If the odor persists, you can purchase odor tablets that sit in the pan and dissolve slowly over time. Sometimes it's not worth the trouble to open the sheet metal just to drop a tablet in the pan. Some systems will have a removable front panel if the coil is a factory cased coil. Some companies buy uncased coils and build their own sheet metal plenum around them. Those are the ones that are hard to get into for a home owner. If you have a humidifier on the system, make sure it is shut down for the summer. Below are two pics of the system in my house (I rent). I installed the A/C onto the existing furnace. I used a Trane cased expansion valve coil, it has a removable front panel. The city I live in requires both drain lines to be connected. You can't see the primary line in the first pic because it is behind the secondary line. The two other plugs are to be used if the coil is mounted in the horizontal position (crawl space and attic installs). The second pic shows the primary line going into the floor drain and the secondary ends next to the furnace. The rust on the furnace bottom was most likely caused by a major water leak or drain back up before the A/C was installed. :wink:

Cased Coil:
Image

Drain lines:
Image
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Postby Mr. Sogetsu » Tue Jun 28, 2005 7:34 pm

I never used odor tablets because where I live most people have well water (so it usually has some smell)and some have so much sulfur in their water it eats away at the coils and I have to replace them after a year or so. If you can smell the water coming out of some of these houses you would not complain about a sour smell. As nascarfool.com said it could be anything, so have it checked out.
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