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  1. #1
    Join Date
    Jan 2007
    Location
    Pittsburgh
    Posts
    181

    UV Light For HVAC

    Had a customer today inquire about adding UV lights to his duct work. Anyone have some good information as to the effectiveness of the lights ? What models are worthwhile? I do recall you have to be careful where you install them, flex connectors and filter media cannot withstand it. Should you have one in the supply and return ? Can all evaporator pans now a days tolerate it ?

  2. #2
    Join Date
    May 2004
    Location
    south louisiana
    Posts
    3,335
    Name:  uv light & mold growth.jpg
Views: 2546
Size:  46.3 KBI usually steer homeowner towards sealing ducts & returns, then adding a media filter.

    IMO, if everything is well sealed..there isn't anything in the duct system that needs uv lights.

    that said...I replaced a ductboard supply plenum that had uv light.
    everywhere the uv light could reach...no mold. where it didn't reach...mold.
    so they do stop growth they reach.
    if you look at the picture,
    on the sides of the plenum..close to uv light...no mold. further on, where light
    couldn't reach...mold.
    the question to me alway was...what is causing mold?

    in this case it was no seal at duct takeoffs at the plenum &
    poor seal @ plenums to equipment.
    condensation caused by hot attic air touching metal take offs
    caused moisture inside (and outside) of plenum.
    ended up changing most of the ductwork too, as mold had grown
    inside flex.
    plenums were changed to sheet metal externally insulated as per
    homeowner concerns.

    hope this helps.
    The cure of the part should not be attempted without the cure of the whole. ~Plato

  3. #3
    Join Date
    Jan 2007
    Location
    Pittsburgh
    Posts
    181
    Wow the UV light subject is defiantly a frustrating issue. Seems like to there is no consistency to anything regarding UV lights and everyone seems to have a different option. At any rate I was ultimately referred to RGF Guardian Air HVAC Cell and REME HVAC Cell. I was offered a substantial discount on the REME for my house so that I can experience it and then hopefully push the sales of them. Seems like this thing is adding peroxide, plasma or whatever to the air, which im not crazy about. Anyone else use these ?

  4. #4
    Join Date
    Nov 2011
    Location
    St. Louis
    Posts
    3,653
    Where installed properly (and everything else as well), they are pretty much scientifically sound.

    To change the bulbs as recommended - expensive.

    I can guarantee they will destroy anything not UV resistant in close proximity (humidifier panel trays).

    I would only suggest if someone has extreme alergies.

  5. #5
    Join Date
    May 2005
    Location
    Lubbock Texas
    Posts
    773
    Gentlemen UVGI lamps are an excellent selection for surface irradiation. But a bad selection for IAQ. Their simply isn't enough time to deactivate a biologic moving at 500 fpm. If installed correctly they will do a good job of keeping the bio slime off of the coil which will maintain the heat transfer efficiency at the evap coil.
    The premise of ventilation is that the OA is clean or of sufficient quality to be used for dilution. Traditional ventilation is somewhat being threatened by the fact that the EPA is changing the requirements for outdoor air quality which is creating non-attainment zones in what is now becoming a significant portion of the country. That means that buildings in those areas will need to clean up the OA before they bring it into the building.
    www.genesisair.com
    Genesis Air Inc.

  6. #6
    Join Date
    Aug 2004
    Location
    North Richland Hills, Texas
    Posts
    14,915
    Quote Originally Posted by genesis View Post
    Gentlemen UVGI lamps are an excellent selection for surface irradiation. But a bad selection for IAQ. Their simply isn't enough time to deactivate a biologic moving at 500 fpm. If installed correctly they will do a good job of keeping the bio slime off of the coil which will maintain the heat transfer efficiency at the evap coil.


    Additionally, if you do install one, insure that EVERY material within about 3 feet of the light is UV rated.

    Some drain pans, ductboard materials, filters, filter housings, wiring, unit insulation, humidifiers, and virtually all flex duct inner liners will be degraded by exposure to UV lights.
    If more government is the answer, then it's a really stupid question.

  7. #7
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,646
    Any organic material that is high %RH for +24 hours has a high potiential for mold growth. Mold spores and organic dust are everywhere. A couple hours of drying out the ducts every 12 hours could stop mold spore from growing. A/c ducts in attics with moisture saturated cooling coils will keep the ducts near saturated for days on end. Completely drying out the ducts by operating the fan a couple hours twice a day stops mold. Fans in the "on" mode 24/7 are most likely to be clear of mold. There are other problems.
    Also ducts in attics during cold weather also have mold potiential from condensation on the ducts when the duct surface is near the dew point of interior air dew point. Again operating the fan several hours each day will dry these surfaces and prevent mold spore germination.
    Good indoor air quality requires fresh air change when occupied. An air change in 4-5 hours is usually adequate when occupied.
    Air filtering to keep the equipment clean. Merv +11 is suggested for inside and fresh make-up ventilation.
    Maintaining <50%RH throughout the inside of a home avoids mold and dust mites. Air ducts spend many hours with 80%-near 100%RH during cooling hours. Several hours everyday of <50%RH everyday will reduce mold/bacteria to minimable level.
    In green grass climates, a whole house ventilating dehumidifier like the Ultra-Aire supplys fresh filtered air, blends the filtered dry air with filtered house air, circulated the conditioned air throughout the home via the a/c ducts. This procces maintains <50%RH throughout the all of the equipment.
    In most cases the 100 watt fan of the dehumidifier can operate 24/7 which keeps everything dry during the "off" cycle. The real long term effects of UV lites on sensitive occupants is unknown.
    Fresh filtered air, keep every dry when not in use, and low circulation is effective for indoor air quality.
    Regards TB
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

  8. #8
    Join Date
    May 2004
    Location
    south louisiana
    Posts
    3,335
    well said teddy bear!
    The cure of the part should not be attempted without the cure of the whole. ~Plato

  9. #9
    Join Date
    Jan 2013
    Location
    Central Arkansas
    Posts
    82
    We always used uv resources equipment in the air handlers when I worked in mfg.. as said before keep all wireing you can away from the area, run the wireing in conduit or shield it some way and if you have to use zip ties make sure they are uv rated. they can also help design a system


    http://www.uvresources.com/

  10. #10
    Join Date
    Nov 2008
    Location
    New Brunswick, Canada
    Posts
    18
    We install a few UV lights and customers have really been happy with them. They have told us that they have helped out with alleges. We have been using Sanuvox.

    http://http://www.master.ca/en/profe...feet&modele=R_

  11. #11
    Join Date
    Feb 2013
    Location
    Fairhope,AL
    Posts
    96
    I have found mold growth in units,with the customers reporting feeling very weak after leaving the home each day. We tried a duct cleaning along with a UV light but after 3 months the problem got better but didn't go away. Eventually we had to replace the unit and ductwork to eliminate the mold permanently. I believe UV can inhibit new growth and odor but does very little if anything for ridding existing mold inside the ductwork and coil.

  12. #12
    Join Date
    May 2004
    Location
    south louisiana
    Posts
    3,335
    "Eventually we had to replace the unit and ductwork to eliminate the mold permanently."


    so....if the ductwork was well sealed to beging with
    ... uv light wouldn't have anything to prevent from growing.

    it is a shame that mastics aren't used properly & the 'sealed' system isn't very well sealed at all.

    I always find it funny that oversized,poorly cut holes for supply boxes that are hidden
    by install of supply grill is so often over looked.
    same for plenum to equipment connections, and return air..both ceiling mounted and chase.

    code says mastic seal should be 'nickel thick' thats tough! I'm a pretty good mastic painter
    and dime thick is hard. nickel thick takes some finesse.
    I'm still trying to perfect that one!

    imo if all ducts were mastic sealed, (I use both paint on and hardcast #1402 mastic tape)
    and above mentioned areas were mastic sealed..then media filter is what works.

    I've worked on lots of jobs..the problem solver aka 'my guys don't have time to do this kind
    of work' I've found what works is painting the mastic WHERE it leaks.
    making it nickel thick, and using a combo of both paint on mastic & mastic tape.
    It isn't the amount of mastic you use, it is where you use it.

    on one job, the guys bragged that they used 8 gallons of mastic.
    (HO bought through Home Depot...need I say more?) the amount of duct leakage
    was reduced from 300 cfm...to 200 cfm. but there were gobs of mastic all over
    the place..they filled in the top of the sheet metal plenums...but not where the top
    of the plenum attached to the sides..you know where the joint is! ha ha ha.

    my advantage is that I test the ducts before and after sealing them.

    not to bash the hvac industry...the job is to get it installed & running.
    ducts are secondary for most.

    electricians that have that same big oversized cut at bath & stove vent
    fans & save a few $$ by buying IC recessed lights instead
    of Insulation Contact Air Tight lights...they need to be responsible
    for the holes in the air barrier for the attic also.

    attic access/pull down stair cases...another leakage/heat transfer issue that
    isn't addressed.

    seems we seal walls pretty good, but sure like to make holes in ceilings!

    I think on the same day that bath fan back draft dampers are installed
    correctly (or at all) will be the same day that recessed lights
    go out of style.

    just my pov
    The cure of the part should not be attempted without the cure of the whole. ~Plato

  13. #13
    Join Date
    Dec 2002
    Location
    Arizona
    Posts
    4,423
    energy_rater_La;

    on one job, the guys bragged that they used 8 gallons of mastic.
    (HO bought through Home Depot...need I say more?) the amount of duct leakage
    was reduced from 300 cfm...to 200 cfm. but there were gobs of mastic all over
    the place..they filled in the top of the sheet metal plenums...but not where the top
    of the plenum attached to the sides..you know where the joint is! ha ha ha.

    my advantage is that I test the ducts before and after sealing them.

    not to bash the hvac industry...the job is to get it installed & running.
    ducts are secondary for most.


    just my pov
    Can I ask what your test out numbers average?
    Make your expertise uniquely valuable.

    Make your influence uniquely far-reaching.

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