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Community and Q&A

Intermittent Odor from Minisplit

Paul Pfeiffer | Posted in General Questions on

Can anyone offer clues as to why my minisplit occasionally puts out an unpleasant odor?  Or any steps I can take to figure it out?

Online searches suggest I might experience odors of dirty sock, chemical/vinegar, or fish/seafood.  To me none of those is accurate (but if I *had* to choose, it would be dirty sock).  I am unfamiliar with the smell of refrigerant–supposedly smells like ether?  I am unfamiliar with that also, but I smelled some starter fluid to (maybe) get an idea and it does not smell like that.  Basically all I can say is that it is an unpleasant but slightly sweet smell that is largely unlike any other smell I know.

I had the HVAC company out when it started, but the odor did not occur while they were here.  It happens a few times a day for a few minutes at a time, so it would be hard to get them here when it occurs unless they stay for multiple hours.

Some reasons I am confident it is originating form the minisplit:
(1) When I smell it I put my nose in the minisplit’s airstream and it is by far strongest there.
(2) I put my nose at the air intake and smelled nothing.
(3) I do not smell the same thing outside (it is right above a window where I can sample the air).
(4) Also the filter is clean.

As I mentioned earlier, the “dirty sock” smell is the closest one of the usual odors even though I wouldn’t call it that.  That is supposed to me indicative of mold, which makes some sense.  The minisplit long had a problem with dripping condensation, although that has been fixed.  It was probably also on at some point while builders were creating a lot of saw dust.  However why would the smell come infrequently in short bursts of a few minutes?  Furthermore I don’t seem to be having any respiratory issues, and I am the type who probably would if it were mold.

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  1. Expert Member
    Zephyr7 | | #1

    You probably have mold or mildew growing on dirt on the coils in the minisplit unit. There might be gunk in the condensate tray too. You can get chemical cleaners for this that will kill the mold/mildew and clear things up for you. Double check that your condensate line is clear though while you're cleaning the unit.

    You probably won't smell a refrigerant leak unless it's a pretty big one. Just ask your HVAC company to "wand" the unit to check for a refrigerant leak. The wands are like electromechanical noses that sniff for refrigerant, and they are VERY sensitive. If the wand doesn't find a leak, you're probably fine. The wands sometimes miss really small leaks (leaks so small you'd never notice anything with your own nose), and if that's the case you'd notice your unit getting low on refrigerant after a year or so. For those leaks, I put some UV dye into the refigerant system, then check for leaks with a black light. The dye glows under UV light, and since it can build up over time, you can find even the smallest leaks this way.


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