UV lights in AC coils?

[Don Wiss]

I'm replacing my central air conditioner with a much more efficient one. (I hope Congress restores the $500 tax credit this year!) One of the options I can buy is UV lamps for the coils. Carrier makes these claims:

- Kills bacteria & mold growing on the indoor coil

- Enhanced indoor air quality

- Enhanced air flow

- Minimizes microbial build-up on coils

- Improves system efficiency

See:

Now I don't yet know how much this option is (or the annual replacement of the bulbs). But is this something worth considering?

Don (e-mail link at home page bottom).

[Dr. Hardcrab]

Figure on about $100 per bulb on replacement costs.....

[geothermaljones]

Check out the UV in the return ductwork... The UV can degrade the plastics oft found on the A/C Coils, namely the condensate drain pan.

geothermaljones

[Old & Grumpy]

[Don Wiss]

Well, if so, that becomes a $300/year expense. There is absolutely no way that the system efficiency could be improved so much that I save $300 of electricity (for summer only usage). The system will already be "up to" 21 SEER.

Don (e-mail link at home page bottom).

[Zyp]

donwiss:

Geothermljones is spot on. You have to be cautious on the evaporator coil pans.

HVAC Tech isn't thinking well. The mold that can grow will inhibit thermal transfer from the air to the coil. UV lights have been proven to increase efficiency in that respect. Albeit over time.

The thing with mold though, is it requires a dark, damp and warm spot to grow. That in mind, while the air conditioning is in operation, the cooling coil hopefully is around 40º F. Not the best for mold growth. But, when standing water is left in the condensate pan, and the system is at rest [or heats during the evening, cools during the day], can leave the opportunity for mold growth.

[hallerb]

wth. =EF=BF=BDBut, when

well turn the heat on occasionally even in the summer.. with windows open.

nice hot furnace air should kill any mold growing in there

[Zyp]

Mold likes it steamy. Generally 98º or better in fact. Turning on the heat occasionally might increase growth. Ever heard of "dirty sock syndrome?" During a heat pumps operation, water left standing in the condensate pan aids the growth of microorganisms and bacteria. The result is the co-toxins produced and the stench as well.

As long as the condensate pan is metal, and, a UVC light is installed in such a manor not to expose other plastic parts to the light, they are a good remedy to eliminate mold growth around the evaporator. But, it is recommend the bulb be replaced annually.

[hallerb]

=EF=BF=BD Turning on the

my point was that with the heat on any mold will dry out and die.

[PaPaPeng]

Nope. Under stress they form spores to be blown to other more hospitable places for regrowth.

On UV lamps I once saw a section of them in the Dollar Store. They never stocked them again. But these lamps are available in novelty stores that sell psychedelic posters and paraphenalia. Perhaps UV lamp bulbs are cheaper there than at a HVAC place.

[Noon-Air]

Wrong kind of UV... wrong light band and temperature

[a]

Indeed - those are "black lights" and won't kill anything.

a

[a]

Honeywell makes some in plenum units:

I am considering one for my main cold air return.

Anyone else have one of these?

a

[a]

Better link:

a

[Dr. Hardcrab]

It killed a lot of my brain cells back in the early 70s!!!

No wait.......that wasn't the black light..........

[a]

I was thinking of that when I posted! Killed a lot of good trips too!

a

[becauseofjunk]

UV does have it's applications.

However, It is expensive for the normal, low maintenance homeowner. UV does have a 1/2 life, something the manufactures have not advertised so well in the residential market. A fact that some contractors themselves have not embraced, I wish I had taken pictures of their faces when I had them actually read the literature.

Evaporator Coil (specifically pan) properly installed should not have standing water so this is not my concern with mold. In fact, it should not be taken into my consideration for recommending a UV system. (But what can I say, I push routine maintenance too.) However, I do live in a rain forest where RH is extremely high. It is the health of the occupants that determine if I recommend an UV system and I do take the time to explain 1/2 lifes, etc....

I find that a properly installed system with a healthy family do not require the addition of UV, there are other, cost effective systems that will keep IAQ well within acceptable limits for a majority of households.

But here is a question for you techies: Ever try to tar your environmental test equipment outside within "environmental norms" to find the house way below (meaning lacking even the slightest trace of natural pollutants such as asbestos or CO found in the area?--and no UV installed?)

[a]

OK - The Honeywell products are not *that* expensive, and UV is used in

*many* water treatment systems and they are not that expensive... UV half-life? No. You mean a radioactive half life expressing the rate of decay? That's like saying light has a half-life, or radio waves have a half-life - they do not. Half life is an expression of the rate of decay of a substance (or a biological system) - not the MTBF or service life of a product. Maybe you mean the phosphors that are used to create the UV radiation has a half-life?

All things wear out - UV bulbs included, but what I like about some of the the Honeywell units is that they can sense when the air is moving and then turn on - extending bulb life past the usual one year.

a

[Don Klipstein]

The UV bulbs for sterilization do not have phosphors. The glass/quartz does becoome a little less transparent to the germicidal UV as the bulb ages.

- Don Klipstein ( [e-mail])

[hallerb]

ing the rate of

he glass/quartz

many years ago hamilton gas dryers had these lamps. many years like

2nd world war