| Dual voltage or multivoltage controls are designed to operate
at 120, 208, 240 or 277 volts. They are used when single voltage controls
can't be used. The concept is that utility inventory could be reduced and
the lineman's job could be simplified by making one control "do it
all". In reality, most low cost dual volt controls work poorly at voltage
extremes because manufacturers must make performance compromises to achieve
the desired price. Good electronic multivolt electronic controls are readily
available but initial cost is a small amount more. The previous (C136.10-1988) ANSI rating of 105-285 volts has been extended
(C136.10-1996) to a 105-305 rating. The extension of the voltage range
recognizes that 277 volt lines used commonly in the USA, may run 10% high.
A word of caution: some low cost multivolt controls will have short life
when used on 277 volt systems.
Tip: If you want to be assured of quality multivolt controls,
add the following to your specifications: Turn-ON and OFF levels shall be the same at 120, 240 and 277 volts. You don't have 277 volts on your utility system? Perhaps not today, but
if you service off-roadway lighting in the USA, 277 volts becomes common.
Or, as your utility expands and/or merges, you may find yourself with
unexpected areas of mixed 120 and 240 volt lighting. No problem, use a
high quality multivolt electronic control. DTL has a detailed discussion paper
available on the advantages and disadvantages of multivolt controls. Call,
fax, email or write for a copy. | 
