A/C Smell - Not Dirty Socks!


Old 10-29-02, 03:27 PM
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A/C Smell - Not Dirty Socks!

We had our air conditioning/heatng converted from a single unit system to a dual unit/zone system about 3 years ago, including new duct work. About 2 years ago one of the units (Lower floor) started emitting a "metallic" smell when the A/C was running.

The contractor has been out and inspected/cleaned the entire system numerous times. They would treat the coils with a "bio- guard" product that would help for 1-2 days but the smell kept coming back. Last March they even went so far as to replace the coils with a specially teated version. The smell has not occurred during the summer but last week we had a cold spell and the heater had to run for 2 days. The weather warmed back up and, unfortunately, the smell is back. If we run the system fan 100% of the time the smell is somewhat diffused but if the fan only runs when the thermostat calls for cooling we get a pretty strong blast of the smell. We do not get the smell when the heater is running

This smell is bad enough that my wife wants to sell the house if we can't rectify it, we're also very concerned about exposing our 1 year old to any contaminants.

The contractor has really been helpful in trying to resolve the issue but I think we're all out of ideas - anybody have any thoughts??

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Old 10-29-02, 08:07 PM
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Hello Skibumtx. Welcome to the Heating & Cooling forum & our Do-It-Yourself Web Site.

I read your posting several times. Not even sure I could begin to offer you assistance but you have requested some thoughts.

The cause could be moisture left on the drain pan if the unit is a vertical heater. Vertical units have a drain pan between the heater and the bottom of the coils. Condensation remaining in the pan and in contact with the drain pan may be a possibility.

The source of the odor may not be in the ducting or with the unit itself. The location of the return air intake may be all or part of the odor source. The odor may seem like a metallic odor as a result of any chemical change as the air passes through the entire system.

Contact the manufacturer for additional information.

The resident heating & air conditioning professionals replying within this forum, may have alternate solutions, suggestions and advice. Check back several times for additional replies.

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Old 10-30-02, 09:39 AM
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Thanks, but...


Thanks for your input. I assume that when you refer to vertical vs. horizontal that you are talking about airflow. If this is the case, I have a horizontal unit.

The air intake is a 2 ft. square column built into the center of the house and has been inspected numerous times. One of the technicians actually climbed from the 1st floor to the 2nd through the column.

The thing that interestes me most is the fact that the smell did not occur until AFTER the heater had been run for a couple of days. Prior to the heater use the system was odor free.


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