UV for HVAC?

[MBAustin]

I searched the forums for prior posts on this topic and the only ones I found are from 2007-2008 so it seems a new thread is in order.

The HVAC tech who did the annual check this year recommended installing a UV light from Dustfree because of mold in/on the unit. It is 8 years old and the prior techs have never mentioned this before. (Our previous HVAC firm was bought out by a larger one recently.)

A quick web search didn't turn up a lot of information regarding pros/cons of doing this (other than the cost - about $1600).

Would appreciate any real-world experience with these systems. TIA.

 

[Aerides]

We recently had our duct work done and they included this. The line item cost was similar, but it was in the bundle of work and not something we could opt out to not get.

We have a new unit and new duct work, so there's no current problem to solve, but it supposedly helps against any mold getting there in the future.

Before this year, I would not have even known they existed, nor been in any rush to go out and get one, if I did.

 

[ShokWaveRider]

I purchased a 120v unit and installed it myself before the main AC fan. It was relatively easy. Drilled 2 holes in the air handler for the lamps and done. The unit I purchased came with a template. Much cheaper than having the AC company install one.

https://www.amazon.com/Sanitizer-Pu...=1662482920&sprefix=furnace+UV+,aps,91&sr=8-5

 

[JoeWras]

In my opinion, they are generally not needed on a residential unit in good working order. But like active electrostatic filters, if you want the extra protection, there's no harm in adding it for insurance.

Commercial chilled water units require this. If you've ever worked in a lab, or data center, and the HVAC person comes to service it, you would have seen the bright blue light when they opened the unit. This is required for those systems because they are actively circulating water, not just dealing with condensate. Chiller systems can sometimes harbor Legionaries disease, hence the UV light.

 

[freedomatlast]

Just another money grab from the HVAC industry selling you something (with an extremely high mark-up) you didn't ask for and didn't know you needed. Did you ever notice that the kids from homes that were germophobic were always the sickest? It's not terrible to be exposed to naturally occurring organic bacteria and inorganic viral material that your system can naturally fight off.

Also, in order for these UV lights to be effective, the viruses and bacteria require from minutes to several hours of UV light exposure before they become disinfected. The rate that air flows through your HVAC system is much too fast for the UV purifiers to be effective.

 

[latexman]

Whatever biological attack/corrosion the UV will kill in the evaporator unit has been going on for 8 years. I don't know your experience, but mine (NC, FL, TX, MI) is the MTBF's for evaporator coils is about 10 years. Have any leaks developed yet? Is the coil copper/aluminum or all aluminum? They usually start as pinholes, and then grow. So, they tend to need progressively larger shots of Freon each season to function optimally once they start leaking until the leaks get so large the coil or system needs replacing.

 

[Bamaman]

I agree with freedomatlast. The HVAC salesmen are often looking for another profit department and UV lights and electrostatic filters are examples. The price estimates for HVAC service are all over the place already--without additional non-needed expenses.

If I have any mold issue, I'll just leave and run my ozone generator that kills molds room by room.

 

[Spock]

Between the lamp strength and exposure time required, I don't see how a UV lamp is going to do much to kill stuff in the moving air stream. It appears that their value is in keeping mold from growing on the surface it's shining on... an occasional cleaning with vinegar or bleach would do the same.
If it were me I'd just go for a high MERV particulate filter.

https://www.epa.gov/mold/does-ultraviolet-uv-radiation-uv-lamps-kill-mold

 

[JoeWras]

Between the lamp strength and exposure time required, I don't see how a UV lamp is going to do much to kill stuff in the moving air stream. It appears that their value is in keeping mold from growing on the surface it's shining on... an occasional cleaning with vinegar or bleach would do the same.
If it were me I'd just go for a high MERV particulate filter.

https://www.epa.gov/mold/does-ultraviolet-uv-radiation-uv-lamps-kill-mold

I thought the light shines on the coils which may have some benefit.

I've looked at over 100 different residential coils through the years. I've never seen a properly operating one covered with mold, or even significant mold colonies. It seems logical that there could be, and sales people pounce on this, stirred in with a little fear.

A little slime in the pan? Sometimes. This is not a problem.

It seems the action of the airflow along with the constant rinsing action of the condensate drop seems to limit mold growth.

Where I have seen mold grow in HVAC units is in flood zones. The electric is off, there's no movement, there are mold colonies in the home from the flood. The spores get into the unit and it is party time.

 

[freedomatlast]

I thought the light shines on the coils which may have some benefit.

I've looked at over 100 different residential coils through the years. I've never seen a properly operating one covered with mold, or even significant mold colonies. It seems logical that there could be, and sales people pounce on this, stirred in with a little fear.

A little slime in the pan? Sometimes. This is not a problem.

It seems the action of the airflow along with the constant rinsing action of the condensate drop seems to limit mold growth.

Where I have seen mold grow in HVAC units is in flood zones. The electric is off, there's no movement, there are mold colonies in the home from the flood. The spores get into the unit and it is party time.

I agree. And in A/C systems that use the same ductwork as the heating system, it would seem that any mold accumulated through the cooling season certainly wouldn't survive the heating season.

 

[ncbill]

Whatever biological attack/corrosion the UV will kill in the evaporator unit has been going on for 8 years. I don't know your experience, but mine (NC, FL, TX, MI) is the MTBF's for evaporator coils is about 10 years. Have any leaks developed yet? Is the coil copper/aluminum or all aluminum? They usually start as pinholes, and then grow. So, they tend to need progressively larger shots of Freon each season to function optimally once they start leaking until the leaks get so large the coil or system needs replacing.

Still cheaper just to replace a coil versus a system, especially since the current refrigerant (R-410A) will be obsolete (just like R-22) by year's end.

2023 residential HVAC systems here in the USA will use R-32 or R-454b.

 

[latexman]

Still cheaper just to replace a coil versus a system, especially since the current refrigerant (R-410A) will be obsolete (just like R-22) by year's end.

2023 residential HVAC systems here in the USA will use R-32 or R-454b.

Is a replacement R-410A coil compatible with a new R-32 or R-454b compressor? Or, is a replacement R-32/R-454b coil compatible with the old R-410A compressor. Idk, but it would be nice to know beforehand to weigh the risk.

 

[Turbo29]

The tech that came to my house last month tried to sell me one of those for $2500. He said, "You have some organic growth in your pan in the air handler." Then he showed me a picture of a little slime mold in the pan.

Having seen the insides of numerous ice machines at restaurants I almost replied, "That's nothing compared to the inside of the ice machine where you are going to lunch after you leave here." I held my tongue and politely declined the UV unit.

 

[RobbieB]

For a hundred bucks, yes. Twenty five hundred, no.

 

[Koolau]

The tech that came to my house last month tried to sell me one of those for $2500. He said, "You have some organic growth in your pan in the air handler." Then he showed me a picture of a little slime mold in the pan.

Having seen the insides of numerous ice machines at restaurants I almost replied, "That's nothing compared to the inside of the ice machine where you are going to lunch after you leave here." I held my tongue and politely declined the UV unit.

Heh, heh, hand the tech a bottle of bleach and a couple of paper towels.

 

[JoeWras]

The fear mongering is out of control.

Mold can be a serious problem but people have to put this in perspective. It is everywhere. I am breathing thousands of spores right now as I type this, especially since I live in the moist Southeast USA.

So once you get the mold out of your coil, what about the drain? The slime molds are the thing that constantly cause the condensate drains to plug up. Run an LED cable down the pipe? /sarcasm

Mold becomes a problem when it festers in moist, calm air, with organics like wood and paper to colonize on. Slow leaks from plumbing, HVAC, and building exterior leaks that land on drywall, wood or paper are the real problem.

Instead of a UV light, I recommend putting money towards leak detector systems that alert you on your phone. Put detectors under every sink and toilet, under the fridge, dishwasher and washing machine, and in every HVAC pan and water heater pan. This will alert you to the flood. As a bonus, it might alert you to the slow leak, which causes mold.

Look under your sinks every now and then and make sure nothing is slowly seeping or leaking down there. Inspect your drywall next to doors and windows. Look for stains or any colonies. Look on drywall ceilings where bathrooms or laundry rooms are above. Have any stains or colors examined immediately.

Then relax.

Now THIS is mold:

 

[Masquernom]

Last year I purchased a home mold test kit. Took samples in the basement area and in the main floor of the house. Results came back with just normal house mold. Nothing of concern. The test kit is a lot cheaper than the UV light. We had a leak from our dishwasher drain once, so I wanted to check it didn't cause mold growth in the ceiling area of the basement below the leak.

 

[ShokWaveRider]

Heh, heh, hand the tech a bottle of bleach and a couple of paper towels.

NEVER use Bleach in an AC unit air handler, it corrodes everything. I forget what the Tech use, it is the active ingredient in Wet and Forget, does the same thing.

 

[JoeWras]

NEVER use Bleach in an AC unit air handler, it corrodes everything. I forget what the Tech use, it is the active ingredient in Wet and Forget, does the same thing.

Agree.

The coils shouldn't really get messed up no matter what, unless you have a problem with unfiltered air getting in. That's a problem. Make sure the returns are tight and well filtered. Otherwise, I don't think they should ever need cleaning of any sort, except maybe a water rinse. Bleach is a really bad idea at the coils. Maybe downstream on the condensate drain it is OK, but I'm even starting to wonder if that's such a good idea.

My 22 year old unit's coils have never been cleaned, and I'm not going to start now. I have a little bit of aluminum corrosion (white) and a little brown rust and/or slime in the pan. This is typical. If it ain't broke, don't fix it.

 

[MBAustin]

Thanks to everyone for the great commentary. After some further internet searching and discussion, DH called the HVAC company yesterday and talked with the tech who had been here last week. Nothing he said convinced us this was necessary for our unit - we'll just continue with the annual maintenance and let them clean it every year. BTW, they were proposing a duct-based light.

 

[Badger]

Many many years ago slime and fungus would build up on the air handler and I could get a service to chemically spray it all off for about $30. It was a real messy job on my upsidedown unit.
I looked into the UV lights during the early stages of the pandemic to mount in the return duct. Installation was real easy and you could buy most units for about $125. An install and repair service wanted almost $1k. A little bit of research led me to believe that it would not be effective due to the lack of exposure time.

Cheers!

 

[JoeWras]

My dad inherited this medical device from my grandfather. Great fun! Cures all kinds of ills! And ultimately useless. Back then it was lumbago or something. Use shocks to cure it. Today it is mold. All kinds of solutions for that problem.

 

[RobbieB]

The UV HVAC stuff got a big boost in the covid times as it could kill the virus.

 

[Koolau]

My dad inherited this medical device from my grandfather. Great fun! Cures all kinds of ills! And ultimately useless. Back then it was lumbago or something. Use shocks to cure it. Today it is mold. All kinds of solutions for that problem.

That contraption looks like it could be a lot of fun. My 7th grade science teacher brought in a crank phone and let the class all hold hands while attaching ourselves in series to the crank output. The teacher would slowly wind that crank, going faster and faster until someone broke the chain. The one who broke the chain had to (got to?) sit down. Eventually two guys (animals, really) remained and would not give up even though their arms were wildly flapping. I forget what the prize was.

Returning you now...

 

[ncbill]

Is a replacement R-410A coil compatible with a new R-32 or R-454b compressor? Or, is a replacement R-32/R-454b coil compatible with the old R-410A compressor. Idk, but it would be nice to know beforehand to weigh the risk.

?

I meant replacing a coil on an existing system is a lot cheaper than buying a whole new system, especially given the current refrigerant phase-out...the refrigerant used doesn't change with replacement parts.