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Home > Resource Library > UV Lamp Performance & Cost
UV Lamp Performance & Cost
Over the years I have spent a lot of time discussing UV lamp operating characteristics with my customers, more than any other topic; and with good reason! UV lamps
are the backbone of any UV sterilizer system. The UV lamp establishes the vessel size, lamp array, generated heat, power consumption and overall cost
of ownership. This means that the UV lamp will determine the performance and cost of any UV system, yet many people are still unaware of just how large a
role the UV lamp has in influencing a unit's efficacy.
When considering a UV system, one needs to be aware of the specific lamp types and the distinct performance differences between them. There are two types
of UV lamps, Polychromatic (medium-pressure) and Monochromatic (low-pressure). Medium-Pressure lamps convert the bulk of their input watts (electrical
consumption) into a broad range of UV-B and UV-A light (above 280 nm, which is ineffective for germicidal disinfection). Low-Pressure lamps convert the
bulk of their input watts into UV-C light at 254 nm, very close to the peak (264 nm) of the germicidal disinfection Curve (240-280 nm).
Medium-Pressure lamp's broad UV output
is better suited for photochemical applications, while Low-Pressure lamp's narrow spectral output makes it ideal for germicidal disinfection.
Medium-Pressure Spectral Output |
Low-Pressure Spectral Output |
Power Consumption
When discussing UV lamp performance, it is important to identify how much of the input watts are converted into "desired spectral
output". In the case of a germicidal disinfection application, you should only be concerned with the output watts that fall into the Germicidal Action Curve
(240-280nm) as shown above. The bar graph below compares the output conversions of four Low-Pressure lamp types and one Medium-Pressure lamp. This graph shows
that the Medium-Pressure UV lamp has the poorest conversion, converting only 7 to 13% of its input watts into useful UV-C output watts, while the Low-Pressure
lamps offer a conversion of up to 40%. Low-Pressure lamps are scientifically proven to be more energy efficient and cost-effective.
Generated Heat
Water temperature is an important factor in successful aquatic life support systems and their efficacy. Often, facility managers are forced to incorporate
chillers to maintain adequate water temperatures due to equipment-emitted heat. Medium-Pressure UV lamps operate at 1600°F while, the most powerful Low-Pressure
UV lamps (amalgam) operate at 180°F. This characteristic alone suggests that Medium-Pressure lamps operate too hot and, therefore, are counter productive and not
suitable for aquatic life support systems.
End-of-Useful-Lamp-Life
This is a term used when the UV lamp is no longer useful and requires
replacement. UV lamp manufacturers express the end-of-useful-lamp-life by identifying the lamp's efficiency compared to its new condition after a specific
amount of continual operating time (80% after 9,000 hours). Efficient operation cannot be determined on whether the lamp "lights" or not. In fact, operating
a UV lamp beyond the manufacturer's specified useful-lamp-life can damage the lamp's ballast and potentially offer no UV protection (germicidal disinfection).
The provided bar graph compares the lamp life of four types of Low-Pressure UV lamps and one Medium-Pressure UV lamp. On average, Low-Pressure lamps outlast
Medium-Pressure lamps by 44%.
When applied to an aquatic life support application for germicidal disinfection, Medium-Pressure lamps are simply not worth the cost. They waste far too much
energy and generate an excessive amount of heat in order to achieve minimal UV-C output levels. Low-Pressure lamps, on the other hand, deliver performance-to-cost
advantages by achieving optimal UV-C output levels while operating at a significantly lower temperature. For germicidal disinfection, Low-Pressure UV lamps are
proven to be the better solution. Please remember, selecting the right UV lamp is critical.
by Stephen Zimmer
Visit UV lamp information for more information.
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