Author Topic: HVAC - Ductless Heat pump mold problems. Asthmatic :(  (Read 556 times)

Tami1982

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HVAC - Ductless Heat pump mold problems. Asthmatic :(
« on: August 23, 2018, 07:25:14 PM »
Anyone work in the hvac industry? Familiar with Mitsubishi ductless heat pumps?

I have had mold problems for three years with mine.  The first one, I was told was over powered for my 500 sq ft house, and therefore never shut down, or completed "cycling."   They came out, masked and plasticed the full of mold box off, until they could come and exchange it.  They put a smaller unit in with a cold plasma air sanitizer unit and it still molded.

This thing pumps out humidity like you wouldn't believe.  For the last year and a half since the new one was installed, I have run a dehumidifier 24/7.  I still struggle to keep the humidity under 50%. 

I have tried:
Lower the temp and lowering the fan, if I do that, I end up with a temp 10 degrees above the temp requested.  I can't seem to lower the fan. 
Auto doesn't work either for maintaining temperatures. 
I don't use a schedule, because if I let it get warmer, it will take hours to get the temp back down.  It's set to hold at 70.
I clean the filter once a week minimum with a vacuum and wash it once a month and let it completely dry before installing.  I've also brought in an air compressor and blown the dust off it. 

The blower and the wire grating is full of mold. Again.

This is a serious issue, as mold is bad for anyone, but the whole reason this was installed was to help my asthma, and needless to say, having a house full of mold spores isn't helping.

I also have two air purifiers, and the dehumidifier has a filter system as well plus the unit itself has the cold plasma air sanitizer and hepa filters.  In 500 sq ft!   I can't imagine what else to do.

The contractor has no ideas why this is happening and offers no solutions.  I'm still working with Mitsubishi, but all I keep hearing is the implication that I'm doing something wrong, that it is somehow my fault.  The contractor tried to imply I was DIRTY, and that it's because I have dogs.  Um. My house is super clean, cause uh, hello allergies and asthma?  Plus, if this thing can't handle me and two dogs, how is it handling FAMILIES? 


Help?

Suggestions?




Miss Piggy

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Re: HVAC - Ductless Heat pump mold problems. Asthmatic :(
« Reply #1 on: August 23, 2018, 07:28:53 PM »
PTF. We have a different (non-ductless) heat pump, and we're battling mold issues in our unfinished basement. Could be coincidence...but I'm wondering if this is a heat pump thing.

Jon Bon

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Re: HVAC - Ductless Heat pump mold problems. Asthmatic :(
« Reply #2 on: August 24, 2018, 08:03:06 AM »
I assume this a minisplit, and not a high velocity units with the super small 2 inch ducts?

Like an AC unit is gonna be a massive dehumidifier as well, so obviously its going to condense a bunch of water. It sounds like this water is not going to where it needs to go? I am not an expect on this but do know a bit.

IIRC the minisplits are going to have a few refrigerant lines as well as a drain line. It is important that the drain line is on the bottom when it exits the house.  Is something going on with your drain line? It needs to have negative grade so it can drain. Is it leaking somewhere or going uphill so it cant drain correctly? Find the drain line and follow it wherever it goes, probably just replace it or worst case get a small condensate pump to get it the heck out of your house. The AC is pulling all the moisture out of the air and then promptly depositing that water into the house.

Hell you got 500 sqft a window unit would do you just fine.

I feel you have lots of options which is something.






fuzzy math

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Re: HVAC - Ductless Heat pump mold problems. Asthmatic :(
« Reply #3 on: August 24, 2018, 08:58:11 AM »
Maybe my perception is off but I don't consider 50% humidity to be that high? My dehumidifier pumps out hot air. So if yours is similar you are heating the air which causes the Ac to turn on which causes humidity and you're stuck in an endless loop. No practical advice sorry, just an observation.

Tami1982

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Re: HVAC - Ductless Heat pump mold problems. Asthmatic :(
« Reply #4 on: August 24, 2018, 10:23:17 AM »
Maybe my perception is off but I don't consider 50% humidity to be that high? My dehumidifier pumps out hot air. So if yours is similar you are heating the air which causes the Ac to turn on which causes humidity and you're stuck in an endless loop. No practical advice sorry, just an observation.

50% is probably okay for most people, but with my allergy to mold, and asthma, it's too high :(  And I also worried about the scenario you describe.  However, if I do not run the dehumidifier it goes up to 70%.  Does that on its own with no "competition."  So at least this way I can keep it down  *some*

It is important that the drain line is on the bottom when it exits the house.  Is something going on with your drain line? It needs to have negative grade so it can drain. Is it leaking somewhere or going uphill so it cant drain correctly?

Hell you got 500 sqft a window unit would do you just fine.


Yes.  I have 8 ft ceilings.  The split is mounted near the ceiling of the room. the drain tube exits near the foundation outside.  It does produce SOME water.  It has been checked multiple times and is installed correctly.

Yes. I had two smaller window units and life was just find.  I only needed two because of my house layout - it's not open at all.  However, when the county comes along, and say they have a grant and will put in the fancy  thing that will improve your allergies/asthma and give you year round lovely heat/cool air, and do it quietly and most cost effectively, you go YIPPEE!  And jump on it.  Only, it costs me more to run than my other units did, or heaters did, because I only turned them on when necessary and this thing has to run 24/7.  And it came with all these issues.

I finally wrote to Mitsubishi directly, over the county and contractor's heads, and they have been very responsive thus far.  Last couple days.  If they can't give me a definitive answer I think I'm going to tell the county to just remove it.

If someone works in HVAC and has experience with this issue, I'd love to hear from you. 

Jon Bon

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Re: HVAC - Ductless Heat pump mold problems. Asthmatic :(
« Reply #5 on: August 24, 2018, 12:24:36 PM »
You reasoning makes perfect sense not blaming you there. I would want a minisplit over window units any day of the week.

Have you googled this? Is this a common problem with this type of unit? This feels very strange to me because AC takes all that water out of the air and should be draining it outside.

Pulling it out and sticking with cheap window units is probably fine. You could probably even sell the minisplit.