CB-- thanks for the reply.Sorry I didn't post more info-- posted it in
alt.hvac. Anyhow, here is the scoop. Unit is a 5 ton 10 seer, upflow
standard (non variable) air handler in a closet upstairs on a two story
house. It was installed when the house was built 4-5 years ago (not by
us-we don't do new construction). I think the people are the original
owners, but didn't ask specifically. We had never been there before. She
said the problem just started last week. When I got there the unit was
off. Turned it on -- HP and strips-- and let it run . Everything fine.
Coil, blower, cabinet all nice and clean. Figured maybe the drain trap
had dried and it was somehow sucking sewer gas, but the drain just runs
outside. I checked the line at the unit and outside and no smell in it
at all. Said WTF. Then, just to check, put the c/u into forced defrost,
went inside and sure enough-- not nearly as bad as they made it out to
be, but definitely noticable. The strips had already been
on, so it was definitely from the coil. I remember seeing a bulletin
from Trane some time back, but as I recall, all it did was acknowledge
there was a problem, and gave no real causes or solutions. I think we
had another unit with the problem, and put in UV lights and ended up
taking them back and refunding the money as they did not help.I am going
to look into it more tomorrow, but I wanted to talk to people here who I
would trust more than some factory rep giving BS. I know Vicki is a
Trane A/S fan, and also NuCalgon. Maybe she will see the post in the
other group, if she can wade through the crap there. Have you ever run
into one doing what this one is? I don't know if this is something
peculiar to Trane or not. I have never heard of the problem on other
units, but around here there are far more Trane HPs than all others put
together. Thanks Larry


Hey Larry,
Sounds like you have a case of "dirty sock syndrome". Typically, the smell
does come from the coil when it defrosts due to the extreme temperature change
which causes micro-organisms to give off the odor. And no, the problem isn't
peculiar to Trane. I have seen it on all the major brands, even some 90% plus
gas furnaces too. Basically, the high SEER equipment doesn't run a high enough
coil temperature to keep the little buggers away. Sometimes a good cleaning
with a acid based coil cleaner and treatment with something like Exodor will
make the problem go away for a while. Most times it will return, but sometimes
not. I think there is lots of theories out there about the source of the
problem and a cure, but I have not seen anything definitive. We have replaced
a few indoor coils with coated coils to prevent the growth of the buggers and
even one or two of them didn't turn out to be a long term solution. I have
heard it said that UV lights are the ticket, but you have already mentioned
that you haven't had success with that method. I did have a powerpoint
presentation that I got from a Trane distributor that had some info that helped
the homeowner understand what was happening and what we knew about it. It had
no real solutions other than to make the customer understand we were doing all
we could and basically, it was one big experiment because what worked at one
job may or may not help the next one. I think CB gave some good advice because
if you have mold growth, there has to be buildup on the coil in the cracks and
crevices. Good luck with it.

Bobby