Re: Halide lamps (short)

Jon Singer (
Sun, 06 Feb 94 12:39:50 PST

Don Burden makes an interesting & important point: the ballast for his
1000-watt Metal Halide lamp is relatively efficient (he reports it
only just warm to the touch). This is expectable, if you think about
it: the ballast is mostly a transformer, and transformers should be
about 95-98% efficient if they are designed well. The bulb, however,
is probably between 25 and 50% efficient, so it must dissipate 500 to
750 watts directly as heat. (I think that incandescent bulbs are 4 to
6% efficient, fluorescent lamps about 24%, and MH lamps perhaps 30%.
In terms of lumens/watt, fluorescents are around 88 when new, and LPS
lamps range up to about 116 if my memory is correct, or about 32%. MH
lamps are somewhere in between. Just as a comparison, the old mercury
lamps, without phosphor, are around 43 l/w.)