Smell coming from Heat Pump


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Old 12-04-19, 05:01 AM
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Smell coming from Heat Pump

We have a new Trane heat pump installed last February, so less than a year old. This year we have noticed a strong odor coming from the vents when the heat is running and the outside temperature drops below 34 degrees (give or take a couple degrees). The blower unit is in the crawlspace which stays dry with a steady low humidity. Last winter when the unit was installed there was no odor during the heat cycle. The Trane installers did come out and thoroughly inspected everything including the coils and drain pan etc. and put it through several cycles including the defrost cycle, but could not replicate the issue, although it was in the middle of the day and the outside temperature was above 45 degrees when they came out. Now every time the temperature drops in the 30ís, the smell is back. They said theyíll had to come back when itís colder during the day to try to smell the odor since they couldnít replicate it. Any insight? We canít be the only ones with this issue.
 
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Old 12-04-19, 05:59 AM
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Although odds are slim that I can help you perhaps giving info on what the smell is might help others help you
re: mildew/mold ,electrical, dead animal etc.
 
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Old 12-04-19, 06:05 AM
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When the heat strips are engaged after being unused for awhile they will give off an odor as they burn of dust or whatever BUT generally that just happens at the beginning of the heating season and won't come back until next year. Couldn't they bypass the heat pump and just engage emergency heat ??
 
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Old 12-04-19, 06:31 AM
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More info about smell

The smell is a musty sour smell, not the burning type of smell when first turning heat on in the winter. To me itís just a chemically musty sour. And the technicians did turn the heat strips on; no smell. And they said the coils were clean. But it was above 45 degrees when they did all the testing. We smelled it again early this morning; it was 32 degrees outside. Under the house where the blower unit is was 62 degrees with 41% humidity. It is so sporadic; only when itís below a certain temperature outside. The smell actually reminds me of the damp sour smell when first switching from heat to ac in the spring/summer, except it keeps happening.
 
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Old 12-04-19, 03:22 PM
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many heating units, not just heat pumps, may have a coating or odors from manufacturing on heating surfaces, ducts, etc... when it gets cold, I'd turn the temp way up and let it heat to the max for some time, maybe up to an hour.
 
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Old 12-04-19, 09:25 PM
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It's a problem that typically affects heat pump systems. It's nick named "the dirty sock syndrome".

Many times the only way to get rid of the smell is to have a new evaporator coil installed that has a different coating on the metal or is mfd of a different metal. You can probably push for warranty exchange.

Dirty sock syndrome
 
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Old 12-05-19, 04:46 AM
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Thanks so much

Thank you to everyone. This is awesome information. Thank you so much!!
 
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Old 12-06-19, 08:55 PM
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Have you checked the filters? Filters often create this kind of odor and simply changing those you can get rid of this bad smell. Musty mildew sour smell in identical to old dirty filters.
 
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Old 12-12-19, 08:14 AM
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Filter Answer

Hi. Yes, I am diligent about changing my inside filters on a regular basis. Weíve been monitoring the smell and it really seems to be when itís a certain temperature (below 40) and seems to be sporadically during the defrost cycle.
 
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Old 12-12-19, 07:34 PM
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Angry Chemical irritating smell

I have something like that going on also. New heat pump summer 2019. Works great with no problems. But this winter, when temperature drops down below 40, there is horrible odor coming out of vents. It is irritating to my throat and burns inside my nose. It is a chemical metallic type odor. Very hard to describe it. Does anyone know what this smell could be and is it harmful to breathe? This has been happening for couple months now. ???
 
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Old 12-12-19, 07:38 PM
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Welcome to the forums.

Did you read post # 6 ?
 
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Old 12-12-19, 07:45 PM
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Hi, it’s not the dirty sock smell. It doesn’t smell like a stinky sock or dead animal. It only happens when it’s very cold. I’m worried if it is harmful to breathe. It is very irritating. Installer came out yesterday and switched out something and cleaned coil I think. But the smell is back tonight as a cold snap is here.
 
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Old 12-15-19, 09:53 AM
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Handy1983, I think weíre battling the same thing...

I describe the smell as sour, musty, chemically. My husband describes it as a chemical smell. We both are smelling it, itís just weíre interpreting it differently. Iím right, of course , but itís the same thing at the same temperatures as yours. Ours is a Trane unit. It was awful a couple days ago when the temperatures stayed around 35-40 all day. I do think it is the dirty sock syndrome from what Iíve read. Iíll keep updating once the HVAC technicians are able to come out and actually smell it. The conditions have to be just right. But, yes, a couple days ago it was so bad and so steady that I started feeling sick from it as well.
 
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Old 12-16-19, 08:00 AM
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Thanks for responding. This feels like such a hopeless situation. I woke up with sore throat again as the smell was here last night as every night that temperatures drop. I am thinking of asking installer to disconnect the auxiliary heat and just use the heat pump only, until this problem is resolved. I don’t know if that’s possible to do. It’s gonna get real cold tomorrow night and I know it’s gonna run the auxiliary almost constantly. Will that help......disconnecting the auxiliary part of heat pump?
 
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Old 12-16-19, 03:46 PM
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I donít know much about the mechanical part...

I just know ours seems to be acting up during the defrost cycle mostly, although the technicians put it through all the cycles including defrost and emergency heat and of course no smell. Itís very frustrating, so I understand.
 
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Old 11-18-23, 09:24 AM
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I came across these posts as I was searching for answers to the frustrating smell from the heat pump system. I have a new system, installed in June 2022. It stated the smell as soon as the temperature dropped to 37 or below, I have narrowed it down to the defrost cycle when the outdoor temp is 37 or lower. A metallic chemical smell that does bother your throat and nose. It's a heavy smell that lingers for several minutes. Yes, the tech came out during a warmer part of the day, forced a defrost and nothing. I believe the heat coils are putting off this smell. I use a Nest thermostat. They are most likely made of some materials that are not up to par for the heat.
 
 

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