Normally/generally the 115v version is used in other than architectural
non-dim installs or where lamp replacement costs are not a large factor. (For those of the 240v world, this would be the same in the 230v verses 240v lamps concept I would think.)
Measure (or have someone qualified to do so measure) the
voltage at the
fixture before adjusting the
dimmer.
Voltage drop or
line voltage at the
fixture is normally at 118v by the time it if starting at 120v gets
thru the
dimmer and all the way out to the
circuit. That's given what you have feeding your building is 120v. If say 125v, this would tend to blow up lots of 115v lamps. On the other
hand if you are starting with a 110v feed to the building as also possible, than the amber
shift of a 120v lamp would be very wasted in your use.
Voltage to the building as with actual
voltage to the
circuit can vary. Make sure who ever is checking
voltage at the
fixture is checking it under load and not alone because the
meter probably won't have enough resistance alone to accurately
meter the
voltage.
115v lamps were designed to both operate slightly over their rated
voltage so as to
gain a higher
color temperature and output - making them seem as if say a 1,000w lamp, and in compensating for
line losses in
voltage that for other 120v lamps normally does not allow it to get up to it's full output.
Next option after
voltage class would be the high output or long life lamps. You should have four choices in this lamp wattage. Again, high output/short life (300 hours when operating at it's rated
voltage be that
voltage fed to the light 115v or 120v) or long life (1,500 to 2,000 hours) when operated at it's rated
voltage. High output is as it says it is, a higher output lamp at the expense of lamp life.
Couple this with the other way of manipulating lamp life verses output - by way of
voltage and you get four choices for a lamp. Say small, medium, extra large and super sized for this lamp by way of lamp life.
750w/115v high output lamps are normally used in the professional industry where budgets are high and lamp costs don't really factor in verses intended use. Such lamps provide the crisp blue
color temperature and high output. Lamp life should be in around the 200 hour per lamp range in actual non-dimmed usage. Given use of a
dimmer, it all depends upon the show for actual usage and dimming of the lamp but as a rough figure perhaps the need to replace one lamp per 1.1/2 seasons.
750w/120v high output lamps are less normally used. Their main usage would be in cases where one needs a high output lamp but are not using a
dimmer or are subject to
voltage spikes and other problems in the
system. The lamp should be still fairly blue but not as hot as that of the 115v version. It should also under normal usage extend the lamp life around 100 or so more hours. (actual formula below note especially the GE note on operation of lamps at greater than 110% of their design
voltage - this is very important.) If you need a high output lamp but don't really have budget to replace 100% of the inventory every say as rough figure, every year and a half, perhaps the 120v version would be a better option as next best.
750w/115v extended life lamps. This would be a better lamp for most theaters that don't have a large budget. Such lamps would last almost as long as say a
Fresnel - almost to the extent that you probably won't notice the difference in lamp life operationg costs. It's going to be a more amber light than the above but should still be hotter than or at least similar to that of normal 750w
halogen fixtures. The lamp life is more in the range of say 1,200 hours in giving up output while at an expected 118v for more lamp life.
750w/120v extended life lamps. I buy them for customers that are strictly install or having problems with
voltage spikes. It's in output similar to that of a high output 575w lamp but much more dim or amber than even that of a say EHG lamp. If installing your fixtures outside in the winter, this lamp will likely be a good lamp. Otherwise for the wattage, while the lamp life would probably be in the 1,800 to 2,200 hour range, the light output is not so good and more in the 500w range.
v = Volts - A measurement of the electromotive force in an electrical
circuit or device expressed in volts.
Voltage can be thought of as being analogous to the pressure in a waterline. The
effect of
voltage on a lamp will cause a significant change in lamp performance. For any particular lamp, light output varies by a factor of 3.6 times and life varies inversely by a factor of 12 times any percentage variation in supply. For every 1% change in supply
voltage light output will rise by 3.6% and lamp life will be reduced by 12%. This applies to both DC and
AC current. Most standard
line voltage lamps are offered at 130v. Since most
line voltage power is applied at 120volts, the result is a slight under voltaging of the
filament. The
effect of this is substantially enhanced lifehours, protection from
voltage spikes and energy cost savings.
Voltage and Light Output: The
effect of
voltage on the light output of a lamp is ±1%
voltage over the rated amount stamped on the lamp, gives 3.1/2% more light or Lumens output but decreases the life by 13% and vise a versa.
Do not operate quartz Projection lamps at over 110% of their design
voltage as rupture might occur. GE Projection, Ibid p.13
A 5% change in the
voltage applied to the lamp results in
-Halving or doubling the lamp life
-a 15% change in luminous flux
-an 8% change in
power
-a 3% change in
current
-a 2% change in
color temperature (0.4% change per1%
voltage.)
Osram Technology and Application
Tungsten halogen Low
Voltage Lamps Photo Optics, p.21