View Full Version : Musty odor when a/c running
10-23-2004, 01:10 PM
I have a problem when one of our heat pump-a/c units runs. Our home has 3 heat pump units, with 2 for the downstairs and 1 for upstairs that is split into 2 zones. They are Trane XL units, with 12 seer, 1.5 tons each downstairs, and 13 seer, 2.0 or 2.5 tons upstairs. (I may off on the tonnage, but recall total tonnage is 5 to 5.5) The home is built on a raised slab, so no crawlspace to worry about. The home is new with 4,400 sq ft, and the units have only been used for about 11 months. All the air handlers are installed in the attics. The two handlers for downstairs are mounted on the attic floor, while the one for upstairs in mounted vertically up on a wall. During this past summer, I noticed that the upstairs unit ran the most as it had the most space to cool. It didn't have any problems keeping the temp at 76, and it would put out a lot of water through the drain to the outside.
The problem started about a month ago when the upstairs unit would come on, we noticed a moldy odor coming from the ducts. At first, it would only smell musty for a minute or so and went away while the unit ran. It has continually gotten worse where it nows smells all the time, to the point I had to shut off the system today so it won't run. My allergies were just killing me. The system has good airflow from all vents, I can't find any duct leaks, and I regularly change the pleated filters every 60 days or so. The only bed and bath occuppied are downstairs, so we don't have any direct bath moisture affecting the upstairs unit.
I have heard of problems with mold and mildew occurring in older systems that haven't been cleaned, but ours is almost new. I can't fathon why we would be having a problem in such a new system. We had several problems with this and another unit, but they were electrical in nature, or so I was told when they were repaired by the installer. I appreciate any suggestions as to what I should ask and look for when I call our HVAC installer. I expect him to come back and rectify the problem, but I also want to try to avoid this from happening again. Any advice? Many thanks.
[Edited by jhinsc on 10-23-2004 at 06:16 PM]
10-23-2004, 08:30 PM
you have dirty socks syndrone..to get rid of it install new coils and have them coated ...if you dont do this it will never go away..
10-23-2004, 09:27 PM
Airman1, thanks for your reply. It appears you are correct. It's funny though that in our previous home, we ran the heat pump system for 2 years with no problems at all. And we're only having a problem with the one system, as the other 2 are running just fine. If the "dirty sock syndrome" is systemic with heat pump systems, shouldn't they all be having the same problem?
10-23-2004, 11:10 PM
airman, this is not questioning your opinion, just adding to it. I recently installed a dual bulb UV in my mother-in-laws A/C. Checked it after 6 months, had no slime in the pan and coil area. (wish you could have seen the original cleaning I had to do!) These things are great!
10-24-2004, 01:47 PM
i too has DSS in my house BUT in only one area..so i double downsized the coil...it came back...i installed a different brand ..it came back...i finally installed a coated coil...gone for 2 years now...DSS seems to be a condition that attatches to an area of your home or the whole house..it will not go away..no one knows what it is exactly...but we know how to fix it..we have a coating system in our company and coat every coil we can because coil coating also reduces electrolysis..if it were my house today all coils being installed will be coated...it costs way too much to correct compared to the cost to eliminate before it occurs
10-24-2004, 07:28 PM
Airman, for the most part, i'm an applied systems or boiler mech. Please explain this coating. Will this coating also prevent the copper from rotting out in swimming pool dehumidification/air-cond system?
10-24-2004, 07:48 PM
Trane puts out a precleaner(kills DSS) and an after treatment for dirty sock syndrome. Install an uv light next to evap coil to kill DSS microorganisms after coil is treated.It has worked for me.
sanuvox uv http://www.sanuvox.com great stuff
10-24-2004, 11:51 PM
uv light will help very little but not eliminate the odor ..in other words dont waste your money on uv lights..companies like technicoat coating at yahoo...the coil must be covered to eliminate porous surface where mold can grow..we have a franchise process called Bronze-Glo...where we can coat the coil and ship it but if you can do it locally (not in Texas) you would be better served
Airman, sanuvox are 90% germicidal/ 10% ozone they really work well. check out their website i was skeptical at first as well. they are completely different than any other uv product out there i have an r-3500 works great
10-25-2004, 11:26 PM
Airman, I have found that spraying copper with "no-mar", purchased from napa will save the exposed copper in wastewater and sewage plants, but I have not found a way to protect the coil. Will your suggestion work?
10-26-2004, 01:10 PM
yes coil coating is done in industrial applications all the time...now back to uv lights..here is my opinion...if they work..they are not needed in a properly designed system...if they dont work they are a waste of money...we have never used them except in testing them and have found out that uv light are installed on most cases to correct a problem proper design of equipment selection would have prevented..so they solve the problem that should never have been there ...in moldy Houston we have not needed them in any of our systems in 20 years beause we aim our design to remove 40 to50% more humidity than what is being installed as a routine here...that being said no light are needed
10-28-2004, 02:16 PM
On the UV light subject. I think some UV lights are pointless in that they lose their intensity in lower temperatures. Most UV lights on the market fall into this category. That said, I bought a "cold cathode UV light" on a whim to see if it actually worked. It did, it has and hopefully will continue to do so. This cold cathode variety costs about double the normal UV light price and has a bulb life of about 1 year. So, am I getting my $'s worth out of the system? Probably not since I service my unit regularly. I would clean my coil at that time if I did not have the UV light anyway. I must say that one side of my coil (closest to the UV light is remarkably clean), but the other side is on the "dark side of the moon" so to speak and needs attention. I do think that it helps with odors to a small extent. I can't say this firsthand as I never noticed an odor problem, but my wife did and swears it is better since I installed the light.
Ozone in any application where there is someone living in a structure is not a viable alternative for odor control. In order for Ozone to be effective against odors, the concentration has to be way above acceptable levels for humans. Ozone is a respiratory irritant and actually breaks down tissue. I don't want to breathe it.
Airman....I do not totally disagree with you on the UV light situation, but I do think that issues such as Dirty Sock Syndrome can and do occur when a system is designed properly. In a HVAC system you have warm and cold air meeting producing condensate in the coil area. ADD a little dust and you have a food source with a bargain buffett for mold. All I'm trying to say is that I have seen properly designed and installed systems have odor problems associated with mold.
10-29-2004, 03:32 AM
and you notice that the dss has occurred more recently..it is irrelevant to design ..it is a house plague attatched to the house..newer equipment designs seem to bring it out..no one knows how to eliminate just stop the problem..in other words fix it but why it is there ..do not know..coating offers the fix without the cure...once coated evap coils we have had zero returns...we are now coating 30% of our coils and selling it as an exclusive our competion does not offer...even if they dont want it shows we can fix a problem that may occur..and we dont use uv lights at all EVER!!
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