We use a lot of the Highbay 4, 6 and 8 Lamp T5HO Fluorescent Fixtures - with Reflectors and Parabolic Diffusers.
They are a much better choice for wide spread area lighting than an HID Highbay or Lowbay, as the linear Lamps have a good light spread - especially with the reflectors and Parabolic Diffusers!
The THD (Harmonics) of the Electronic Ballasts does not result in anymore L-N Load Current then what is produced by a typical CWA Reactor based HID Ballast.
Maybe an additional 5% if the Circuits are loaded to Maximum, and the Ballasts are "Noisy" (>20% THD).
The typical tradeoff for a Lighting Retrofit (old Probe Start Metal Halide fixtures replaced with T5 HO Fluorescents) is a drammatic reduction in drawn Kilowatt Hours, while still retaining the same level of Light (and a much "cleaner" light output too!).
Clients receive conservation + reduction benefits, and typically the retrofit pays for it's self within 2 years.
The Ballasts driving the Lamps on the fixtures I typically Specify / Design with, are "Programmed Start" instead of just plain old "Instant Start".
The Lamps are started in the "Hot Cathode" mode, and as they are run, the Cathode Heating is reduced accordingly.
This results in excellent Lamp efficiency + effecacy (read: high, stable light output), best life operation, and since the Cathodes' heat is reduced during operation, the total drawn wattage is reduced at that time
Standard "Rapid Start" methods are great for Lamp operation, but power is wasted by continuously heating the Cathodes at the same level.
"Instant Start" methods use "Cold Cathode" operation, but the Lamps are not running at their optimum output.
The Cathodes are not heated, so there is no "Parasitic Load", or "wasted power" to heat the Cathodes; the tradeoff is lower power drawn through the Lamps, and results are lower Light output.
Scott
