Mike (Trumpy):The only down side to these fittings that I have experienced, is temperature changes can cause the light output of the tubes to vary slightly, but it is not a big variation.
This is a very valid statement, as when we use Fluorescent Lamps inside of Walk-In Freezers, where Temperatures are -10ºC / 14ºF and down, the light output is reduced by 10% to 20% - depending on the ambient.
The Ballasts are Program Start, and incorporate an additional heat generating circuit, to keep the Ballastry + Lamps somewhat warm, without becoming a large contributor to heat.
On the Walk-In Freezers, I typically will set a "Target" illumination (in Foot-Candles) for 120% the desired average Foot-Candle level.
For example, if the desired level in the Freezer is to be 30 FC, with highly reflective walls, and fixtures mounted in rows at +20 feet A.F.F., I will set my application's target average level at 40 FC.
If the reflectance is less (darker points, like what would result from brown cardboard boxes on shelving), and/or the mounting height is >30 feet, then I adjust the average FC target by as much as 160%
For example, if 30 FC is the desired target average in the Freezer, I set my application's target to 50 FC average.
No Manufacturer has photometrics for the expected reduction in sub zero environments.
They all say their fixtures work in those environments - which they do, just no one has taken the effort to give actual derated levels.
We have been kind of finding out as we go, to come up with the +20% - +60% figures. So far they have been rather accurate when applied to the typical fixtures we specify and install.
Scott