Here’s some discussion of the most popular questions I receive regarding sunbed voltage and tanning times:
How does voltage affect lamp performance?
Almost all sunbeds marketed in the U.S. employ pre-heat choke ballasts rated for a given wattage at input voltage of 220V. This ballast is a simple transformer, so increasing input voltage will increase wattage (electrical consumption) and, to a certain extent will increase irradiance (output) from the lamps while increasing the heat generated by the sunbed’s electrical system. The pre-heat choke ballast regulates current to the lamp, not voltage, so the lamp “sees” any voltage change to the ballast. Higher voltage to the lamp makes for more rapid consumption of emissive material on lamp coils = earlier lamp failure, and faster degradation of the UV-emitting phosphors inside the lamp = shorter lamp service life. JW North America rates service life as that point where irradiance has declined 30% from initial levels.
The discussion above does not apply the same way to a sunbed employing rapid-start magnetic ballasts. This style ballast compensates for input voltage variances within a fairly wide range. Increasing voltage to a rapid start system will increase heat without any benefit.
If the equipment manufacturer recommends running your bed at 230V, it should be because that is the way the bed was tested to arrive at the maximum timer interval, or time to deliver four (4) MED (Minimal Erythemal Dose). Increasing voltage beyond 230V then shortens the time to four MED through increasing lamp output … adulteration of the product. In this example, and assuming the original equipment maker (OEM) employs the industry standard 220V choke ballast, the OEM has already decided to accept shorter lamp service life, shorter lamp physical life and increased heat to get the desired timer setting. Increasing input voltage further will add more heat; will reduce lamp life and usefulness further, but with diminishing increases in output of the lamps. The example below demonstrates the diminishing returns and escalating costs relative to input voltage:
At 12 minutes into the session … that is, if the original testing that leads to the maximum timer setting is done correctly. OEMs typically perform testing for timer setting with lamps aged a few hours, so after installing a new set of lamps, we advise shortening sessions maybe 10% for the first 50-100 hours to compensate. Sunlamps depreciate more rapidly during the first 50-100 hours, and then the rate of decline flattens.
A sunbed delivering four MED in half or 70% of the max session time shown on the bed label (and in the accompanying manual) is “defective” per FDA regulations and per good manufacturing practices. The industry standard is to market and deliver sunbeds that are NOT defective. Possibly, the method of determining that a bed delivers four MED in substantially less time than called for on the label needs review; or possibly, the bed has been fitted with lamps that are entirely too strong for the equipment design. In any event, exposing a tanner to a full-session UV dose equaling eight (8) MED (your “50%”) is irresponsible, and creates potential liability for everyone in the supply chain who contributed to the over-long session, and can be damaging to the tanning industry as a whole.
Michael Stepp joined Wolff System as President in 1998, bringing years of lighting industry experience with GTE Sylvania, Osram Sylvania and Philips. Married for 38 years, he has a daughter and granddaughter.
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