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  1. #1

    Deteriorating system components exposed to UV light

    Has anyone else had problems with UV lights, EAC's and the other "new" air cleaners deteriorating the hydrocarbon based components of their HVAC systems? I just had another customer show me a filter that looked like Swiss cheese after being exposed to a UV light. The UV light and the ozone will react with any plastic materials such as filters, pans, wire, mastic, flex duct, etc. I would like to know how widespread this problem is and what people are doing about it.

  2. #2
    Join Date
    Aug 2004
    Location
    North Richland Hills, Texas
    Posts
    14,915
    It is very wide spread because most UV light systems get installed in the WRONG part of the system.
    It seems that in my area, no installers have the slightest clue where they go in the system.
    Every one of them I have seen was installed in the return plenum before the filter, or in the supply plenum. UV lights do absolutely nothing good for a system in those location.

    Salesmen love adding them to systems because they are high profit margin, but talk them up as doing something that the UV light has no hope of doing. UV lights will do almost nothing to stuff that is traveling in the air because the air moves to fast to allow enough exposure time.

    The only place a UV light system can do anything positive for the system is if it is shining directly on the entering air side of the indoor coil, and is located within a foot or so of it.
    If more government is the answer, then it's a really stupid question.

  3. #3
    Well said. One of the benefits of using some of the Photocatalytic Oxidation (PCO) designs is that you aren't trying to treat the air stream with the UV light and the design is focused on illuminating the internal coated sections of the photocatalyst. It treats the conditioned space on a longer exposure basis. Of course, some designs do actually try to condition the air stream - requiring much higher energy consumption to try and "zap" the bad stuff. Problem is that the bad stuff might not be constant in the air stream, leading to an overload of the good stuff - which can be just as bad for the occupants!
    A little vodka is ok, a liter can kill you if you drink it all at once!

  4. #4
    Join Date
    May 2005
    Location
    Lubbock Texas
    Posts
    773

    Thumbs up

    Nice subject for a change and everyone is right on the money from what I have witnessed so far in a lab setting and in the field. Most HVAC manufactures have changed the formula of the plastics they use in current coil boxes in residential systems to compensate for the use of UVGI Lighting. For the old systems depending on the UV wattage the bulb produces it will break down the pans if it has a direct irradiation on the pan in 3 to 5 years.
    In the returns after at least merv 10 filtration is the place in a system that the highest kill rates can be achieved for this reason. A low out put bulb is the most common bulb on the market. Its optimum working temp is around 80 degrees so if the same bulb is put in an air stream of 55 degrees is reduces the output of the bulb by almost 40%. As what Mark said the only place to install just UVGI alone is in the coil box after improved air filtration.
    As far as filters being burned by the UVGI lighting there are benefits of illuminating the back of the filter in a controlled commercial setting for biologic protection but never in a residential unit the risks of someone being burnt by the lights are too high. This is why in our residential line we use polished aluminum shields to protect the filters and project 100% of the light to the PCOs.
    From what I have seen from field installs a 36 watt UVGI light will burn through a filter in about 3 weeks if the light is left on with no air flow. The systems I have seen with constant air flow have gone over 120 days before the holes start in the filters, like a variable speed system chiller system with VAV boxes and such.
    Field testing by us and other universities show in PCO technology the higher the temp and the higher the humidity the better the removal rate is. So yo need to keep this in mind when installing any ones PCO system.
    I am a nut with aluminum tape I tell people if in doubt cover it with foil tape. The only other technology I have really witnessed a lot of damage was in a very large (unnamed casino) they were using a very large commercial EAC System and in the beginning they said the could see some improvement in the smoke particulate then after about a year they started getting dirt clods falling out of the supplies on to the slots. What had happened was the magnetized particulate was collecting in the supplies that was making it passed the Merv 6 pleated filters they were using in the HVAC and was sticking to the supply ducting. The dirt in the supplies got so thick in a years time the air flow was rolling it in to balls and pushing it out of the supplies. They are in the process of replacing those ducts right now. It was a mess. Nothing bets good filtration humidity control and proper fresh air and sometimes thats not enough then you supplement with UVGI or UVGI with a PCO. Depends on what you want to achieve in the treated environment.

  5. #5
    Join Date
    Mar 2004
    Location
    Austin, Texas
    Posts
    1,959
    genesis -

    I must be missing the most basic logic here. When I go look at your 'systems' on your web site I see what looks like UVGI lights sandwiched between two filters. How does the UVGI ever reach the coil from between the two filters? Are these units to go under a furnace? How would the UV light reach past the blower and furnace to ever see the coil?

  6. #6
    Join Date
    May 2005
    Location
    Lubbock Texas
    Posts
    773
    CX the top side of a WO units is a pleated mesh screen than has the TIO2 on it. The bottom of the unit is a merv 12 4 inch filter.And one of our basic beliefs in the office is a properly maintained system is the best system in residential units. And if you have a clean evap and coil pan to start with and add our UV/PCO system the improved filtration and the combination of the UVGI and the PCO your coil box should stay clean and mold free. The last testing we did't with the Army was showing on old removel we were hitting in the range of 90% plus in a single pass at around 1800 CFM
    We are developing a system that sets on top of the coil for some one. But we are still in the testing phases of it, and still looking at proto types.

  7. #7
    So, you have confirmed exactly what this thread is about - UV lights will destroy any materials made of hydrocarbons exposed to the UV lights. This is a major problem since buyers are not informed of this potential damage or the costs involved.

  8. #8
    Join Date
    Aug 2012
    Location
    NE wisconsin
    Posts
    403
    Quote Originally Posted by breathe easy View Post
    So, you have confirmed exactly what this thread is about - UV lights will destroy any materials made of hydrocarbons exposed to the UV lights. This is a major problem since buyers are not informed of this potential damage or the costs involved.
    Proper installation will result in no damage, far enough up in the return drop and you have no direct exposure to the light, put shielding in to protect non uv resistant materials or cover in foil tape. Those filte earlier in this thread must have been right next to the bulb. The company I work for installs a lot of uv lights and with proper installation and educating the customer a little we never have any problems. But I have seen them installed wrong by the other guys and it usually results in the filter deteriorating, but I've never seen them as bad as the photos posted earlier.

  9. #9
    Join Date
    Aug 2010
    Location
    SouthEast Texas Gulf
    Posts
    15

    UV Lamp location is key

    Quote Originally Posted by breathe easy View Post
    Has anyone else had problems with UV lights, EAC's and the other "new" air cleaners deteriorating the hydrocarbon based components of their HVAC systems? I just had another customer show me a filter that looked like Swiss cheese after being exposed to a UV light. The UV light and the ozone will react with any plastic materials such as filters, pans, wire, mastic, flex duct, etc. I would like to know how widespread this problem is and what people are doing about it.
    The placement of the lamp (s) I believe is key. Lamps should be installed on the output side of the coil (Per Carrier pub:63UV-LA3). I sell and install UV lamps on occasion, I even have installed one in my home. I have never had a problem with plastics in the system, I believe that the new plastic pans are uv and chemical resistant. Flex duct might be a problem but I have not seen that as most of the systems I work on are metal pipe or ductboard. I use a TIF 3710 to check uv lamp operation; when installing a new bulb I mark the readings on the coil, averaging readings on both front and back side of coil. If the bulb is less than 1 year old and reading low because the bulb is dirty I clean it with alcohol, carrier sells a cleaning kit. I have seen a big difference in only 6 month of using a uv lamp on some systems. Usually the coil and pan look like new. I also recommend a good filter, like an Aprilaire, be installed at the unit. I have never seen an Aprilaire filter degraded by uv light, even when installed directly on intake of a fan coil. I always install the uv lamps between the coil and blower not the coil and filter, even so when you remove the filter you still get a dose of uv radiation but I have not seen any harm even after a year of same filter being exposed to uv.

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