HotConductor, I understand what you're saying but I am not talking about using the workhorse ballasts, which ARE rated for multiple lamp types.
I am referring to the idea of
"Therefore I can continue to install the 34 watt t12 magnetic ballasts. I like them because they are cheap and reliable."
If those ballasts are NOT rated for use with t8 lamps, then I stand by my position that it is reckless and/or unsafe.
And need I remind anyone that deliberately installing a non-rated lamp/ballast combination would not only void the listing of the ballast but would be a Code violation. (ref. 1999 NEC, the one I have on hand,)
Art. 110.3(b) "Installation and Use" "Listed or labeled equipment
shall be installed and used in accordance with any instructions included in the listing or labeling."
So if the ballast labeling does not indicate that a T8 lamp is suitable a red tag would be given (if inspected) and if anything should go wrong this violation sets up a very strong position of liability.
Thank you Larry. Your post went up as I was composing mine, and I agree with you on everything except the maybe.