Apr 29, 2020 UV-C Lamps: When and How to Replace
Hidden away somewhere in your facility’s AHU plenum or HVAC duct is a UV-C lamp struggling to perform its primary disinfection task.
Not surprisingly, researchers believe eight out of every 10 building engineers forget to regularly replace their facility’s UV-C Lamps. Said differently, 80% of facility managers are NOT reaping the many benefits of germicidal UV-C highlighted below.
UV-C lamps, while typically thought of as mysterious, are in fact manufactured on the same types of machines as fluorescent lamps and operate identically. (See the image to the left where the top UV-C blub looks nearly identical to the standard fluorescent lamp.)
However, UV-C lamps use doped quartz glass, an expensive type of glass that does not include the internal phosphor that makes fluorescent lamps “glow” to produce visible light.
In other words, because the UV-C wavelength (253.7 nm) is invisible to the human eye, the blue light that one sees represents only 5% of the total output of the lamps. So you can’t “see” if the remaining 95% output is reading “full” or “empty.”
So unlike the dark or flickering lamp above your desk or in the conference room, the visible light emitted from a UV-C lamp is NOT a useful indicator of its performance.
Said differently, UV lamps will continue to emit the blue light long after the UV-C output has decreased, even by more than 50%!
IMPORTANCE OF UV LAMP REPLACEMENT
UV fixture design, while similar to fluorescent fixtures, is different in a number of ways. One of the primary differences is the environment in which these HVAC type fixtures are meant to operate. Its stainless steel construction is one of the main differentiators; however, the functional life difference has to be its electronic ballast design.
Being in a cold, damp environment requires a robust ballast that can withstand the fluctuating electrical demands of the lamp as its surrounding air cools, warms and moves. Also, the damp environment provides an additional challenge for the electronic components and necessitates the use of a complete waterproofing… or, that it be mounted remotely outside of the plenum.
The applications of UV-C lamps are many, as mentioned, they are used in virtually all building types for HVAC surface irradiation to keep cooling coils and plenums clean, along with air filters – disinfected for “capture & kill”, and for infection control (i.e. the “on-the-fly” killing of pathogens).
Another popular use since the 1940s is upper-air UVGI systems for in-room killing of airborne pathogens. In all cases, maintaining the lamps so that the installed systems are emitting the proper amount of UV-C energy to accomplish the goal of the application, is of course imperative.
WHEN TO REPLACE?
Most lamp manufacturers (Phillips, GE, and Sylvania, etc.) recommend:
- removing and replacing UV lamps every 9,000 hours or 1 year (annual preventative maintenance [PM] schedule).
- Most quality lamps will emit at least 80% of their original UV-C output at the end of one year.
- An annual schedule consolidates change-outs into one service interval, allowing the facility to purchase lamps in larger quantities to save money and time.
In “remote” systems (mechanical rooms, interstitial spaces), there are accessories available for continuous monitoring of lamp-ballast functionality (UV-Com lamp ballast monitor™) that communicate with building management systems. Monitoring of critical environments (hospital isolation rooms, etc.) for whole system performance and lamp-on hour meters (UVReport™ stationary radiometer) can be provided as well.
The locations where UV-C fixtures are typically applied have unfortunately created a situation where the lamps are “installed and often forgotten.” This has led a few users to believe they don’t work when in actuality, the lamp’s useful life has simply passed. Whether UV-C fixtures are installed at the air handler manufacturer’s factory (common today) or retrofitted into an existing system, or even installed in the upper air of a room, UV-C should be installed, and immediately added to the building PM programs. This way it’s not forgotten and its many benefits can be enjoyed for many years to come.
BEST PRACTICES FOR REPLACEMENT
When it comes to replacing UV-C lamps, certain practices should be avoided. A common mistake many make is replacing them only as they stop functioning. This method is highly labor intensive and inefficient, requiring routine inspections of the individual lamps to determine the need for replacement.
Furthermore, as that 9,000-hour mark passes, as noted above, the lamps’ germicidal effectiveness begins to diminish, potentially causing HVAC/R system performance to be compromised.
A more advisable solution is to establish an annual replacement schedule whereby all lamps are methodically swapped out at a designated interval. Such a strategy eliminates the need to carry a large inventory of replacement lamps (with the exception of a few spares in case of breakage). Instead, it offers plenty of lead time and a more logical routine or schedule.
Annual replacement is also more cost-effective. Individual replacement means higher lamp and labor costs and downtime during each procedure—not to mention frequent monitoring by staff members. An annual schedule consolidates change-outs into one service interval, allowing the facility to purchase lamps in larger quantities to save money and time. This also reduces the need, with the exception of critical environments, to invest in an expensive radiometer or other equipment to monitor individual UV-C output. The knowledge that lamp replacement will simply be “taken care of” each year will allow peace of mind for building managers.
Most important of all, annual replacement guarantees that UV-C output will never fall below effective levels and HVAC/R efficiency and IEQ will not be compromised. By implementing such a schedule, you are doing your duty to protect both your building occupants (and your pocketbook), as well as your equipment from the efficiency-robbing effects of microbial buildup.