Wattage & Power

Does more wattage equal better tanning capability, or just more power consumption?

Wattage is primarily a measure of power consumption, not necessarily irradiance (output). The wattage of a low-pressure fluorescent lamp is determined by the lamp design and, more importantly, by the ballast that powers it. All of this is influenced by the input voltage to the ballast/lamp system. In simple terms, the ballast will determine the system wattage, so installing a 100W lamp in a higher-wattage ballast (say 120W/1200mA) will result in approximately 120W of power consumption.
Wattage is also a measure of heat. One watt = 3.412 BTU. British Thermal Units are a heat value standard and you see this term commonly used in air conditioning systems. Total wattage of a tanning unit at actual input voltage, including fans and other onboard electrical devices, tells you the BTUs of air conditioning required to manage the heat load it creates. This is something to keep in mind if you are “upgrading” a few smaller beds to larger ones with more lamps/wattage/BTUs – your HVAC person should be consulted to be certain your A/C is adequate.

All other things being equal, increasing fluorescent sunlamp wattage results in increased output and power consumption.

Our industry is moving to sunlamps with higher wattage as opposed to the standards of 100W and 160W. The standard lamp envelope is F71/T12/Bi-Pin. In its 100W iteration, the internal environment of the lamp is tough; at 160W it is almost hostile. Increasing wattage further magnifies this effect, thus a shorter service life to be expected when wattage is increased, due to amplified phosphor degradation and, to some extent, physical wear and tear. Increasing wattage will increase UV output of the lamps, but not in a linear sense. Increasing wattage (and heat) past optimal lamp design by 10% yields about 5% greater irradiance and 10% higher power consumption. Keep in mind that in each of these scenarios, the lamp is the same size, you are just demanding more from it.
So, the answer to the question is: All other things being equal, increasing fluorescent sunlamp wattage results in increased output and power consumption. That is not to say that it is wise to install 100W lamps in a unit designed for 160W lamps … cathode and mount designs are quite different for these two lamp styles, and this kind of misapplication will certainly disappoint you. Whether a sunlamp is a reflector or full-coat model, the wattage does not change due to the reflector … radiant heat is directed differently by reflector lamps, but there is not more of it.
Since tanning systems of any size (or wattage, or UV source) can only deliver a maximum UV dose per session equaling four (4) MED (Minimal Erythemal Dose), there are reasons for higher wattage:

• For aesthetic reasons, greater lamp irradiance allows for longer exposure distances from the tanner so the unit can look the way the designer wants (or just be bigger).
• Economically speaking, greater irradiance allows for shorter maximum session times in like-sized equipment, thus increasing tanner throughput and salon revenue.
• Also, in same size equipment with the longer exposure time, higher wattage/output lamps allow fewer lamps and other components, resulting in lower manufacturing costs and a lower price for the equipment.