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UV light for mini split

jjrbus

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Joined
Dec 8, 2018
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606
Location
Florida
Has anyone actually installed a UV light in a mini split to combat mold. I have been searching and most of what I find are advertisements for lights.
 
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bonneyman

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Apr 22, 2010
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8,757
Location
Desert SW
I've heard of UV lights installed upside down in an evap coil to kill mold spores and bacteria, but it's buried in the unit so no chance of human eyes being exposed. I guess something similar could work for your issue.

Perhaps this article might help.
 

aggie113

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Jul 22, 2015
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467
Location
San Antonio, TX
I use a small electric sprayer and a bib kit I bought on Amazon to do a yearly cleaning on the minisplit in the garage. Even cleaning the filters on the regular it still gets nasty on the blower wheel.
 

fitter30

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Jun 23, 2019
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Location
Peace Valley,mo
The problem isn't the mini it's the RH. Either lower the set point add dehumidifier to lower the RH below 50%. Or lower the set point. Infiltration is not your friend.
 
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jjrbus

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Dec 8, 2018
Messages
606
Location
Florida
I use a small electric sprayer and a bib kit I bought on Amazon to do a yearly cleaning on the minisplit in the garage. Even cleaning the filters on the regular it still gets nasty on the blower wheel.
I have taken the blower wheel out and now have bought the sprayer and bag. The issue I have now is my minis are mounted up high, I am 78 and I can see getting up and down a ladder is not going to be happening much longer.
 
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jjrbus

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Joined
Dec 8, 2018
Messages
606
Location
Florida
The problem isn't the mini it's the RH. Either lower the set point add dehumidifier to lower the RH below 50%. Or lower the set point. Infiltration is not your friend.
I live in FL it is a swamp. After doing some research the plastic used in the blower wheel is porous and a perfect home for mold. Nothing in the mini evaporator gets mold on it except for the wheel.. People who seem knowledgeable claim it is common in draw through AC designs.
 

fitter30

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Jun 23, 2019
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Location
Peace Valley,mo
I live in FL it is a swamp. After doing some research the plastic used in the blower wheel is porous and a perfect home for mold. Nothing in the mini evaporator gets mold on it except for the wheel.. People who seem knowledgeable claim it is common in draw through AC designs.
Moisture on a AC coil is 100% when the cold air starts to warm up/ mix with room temp rh drops( higher the temp the lower rh). Air temp is easy to drop, latent heat is the hard part.
Need to ask our electric provider if they offer a energy audit that includes a blower door test. Will tell how tight the house is. Guess you have a crawl space? Is it sealed with a dehumidifier?
 

bluedog225

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Jan 31, 2012
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3,241
Location
Texas
I thought dry mode or having continuous air flow to dry it out was the answer.

Maybe some colloidal silver on the surface if it is porous. Wonder why they would do that?
 

Chuckster in NJ

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Jan 26, 2010
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Location
Hunterdon County NJ
Wouldn’t the UV light degrade the internal plastic and rubber components?……… I know that UV light breaks down the polymer chains in plastics.
Ozone has been known to destroy plastics and rubber too.

BTW! Mold survives on DARK, DAMP area with NO AIR MOVEMENT so if you take away one of these mold will go dormant and will not survive.

TIP! "IF" you have a mold problem in a mini split I suggest checking out a cleaner spray that they use on HVAC systems and use it on a monthly basis.……. Condensate pan tablets and condensate line cleaners will also work to knock down mold.
Check out www.supplyhouse.com
 
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jjrbus

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Dec 8, 2018
Messages
606
Location
Florida
Moisture on a AC coil is 100% when the cold air starts to warm up/ mix with room temp rh drops( higher the temp the lower rh). Air temp is easy to drop, latent heat is the hard part.
Need to ask our electric provider if they offer a energy audit that includes a blower door test. Will tell how tight the house is. Guess you have a crawl space? Is it sealed with a dehumidifier?
No crawl, house is CBS built in 86, all new windows and doors. Minimal insulation.
 
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jjrbus

Well-known member
Joined
Dec 8, 2018
Messages
606
Location
Florida
Wouldn’t the UV light degrade the internal plastic and rubber components?……… I know that UV light breaks down the polymer chains in plastics.
Ozone has been known to destroy plastics and rubber too.

BTW! Mold survives on DARK, DAMP area with NO AIR MOVEMENT so if you take away one of these mold will go dormant and will not survive.

TIP! "IF" you have a mold problem in a mini split I suggest checking out a cleaner spray that they use on HVAC systems and use it on a monthly basis.……. Condensate pan tablets and condensate line cleaners will also work to knock down mold.
Check out www.supplyhouse.com
It is not just me with a problem, there are thousands of videos and posts online about mini blower wheels with mold problems.
 

Diesel Dan

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Joined
Jul 21, 2013
Messages
2,457
Location
TN
It is not just me with a problem, there are thousands of videos and posts online about mini blower wheels with mold problems.
keeping my blower cages clean is a battle as well.
What I recently started doing is adding a layer of bulk two layer furnace filter on top of the inlet of the wall units. It has made a noticeable difference in keeping the cages clean and you can see the filter material darken from the contaminates they catch. These are in the living space, not a shop. The attached image is similar to what I use, friend that does commercial hvac gave me a few cutoff pieces to try and I'll order me a roll to keep on hand.
 

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jjrbus

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Joined
Dec 8, 2018
Messages
606
Location
Florida
keeping my blower cages clean is a battle as well.
What I recently started doing is adding a layer of bulk two layer furnace filter on top of the inlet of the wall units. It has made a noticeable difference in keeping the cages clean and you can see the filter material darken from the contaminates they catch. These are in the living space, not a shop. The attached image is similar to what I use, friend that does commercial hvac gave me a few cutoff pieces to try and I'll order me a roll to keep on hand.
It's a thought. Seen a guy in his shop made a 8X2 foot box over his wall unit. All filters
 

aggie113

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Joined
Jul 22, 2015
Messages
467
Location
San Antonio, TX
I thought the higher filtration led to poor airflow for these units. My bedroom minisplit wheel is due for a cleaning. First time in 4 years for that so not bad. The garage unit requires a cleaning yearly. Links to the equipment I use bib and an electric sprayer
Even if the cheap electric sprayer only lasts a year it is still cheaper than having someone come out and clean a unit.
 
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jjrbus

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Joined
Dec 8, 2018
Messages
606
Location
Florida
The cheapest mini split cleaning in my area is $120 to $250 per unit, I have 3 separate units. I see a pro on You tube clean a mini including removing and cleaning the blower wheel in an hour.
 

sarcastoplasm

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Joined
Apr 4, 2026
Messages
2
I’m an HVAC tech in southwest FL so I deal with this issue a lot. Unfortunately anything strong enough to kill mold or prevent its growth will also degrade the plastic polymer of the blower wheel. There are products out there from Rector Seal (Dust Free), Diversitech, and Fresh Aire but they have mixed results with poor reliability. I think the best option is to have it cleaned periodically. You can remove the wheel to clean it but you have to be ginger careful, or you can get a bib and clean in in place.

Keep in mind any time it’s disassembled you run the risk of something not working right when it’s put back together again. Even if you do everything “correct”.
 
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