Planted Tank Guru
Join Date: Jul 2008
Location: East Lansing, MI, USA
The ballast because it effectively reads the lamp connected to it and provides the proper electrical requirements for the lamp. Some use a look up table and some measure the filament signature.
An electronic ballast for T5HO can run T5HO properly, and drop down to run T5NO correctly or slightly over driven.
An electronic ballast for T5NO, can run T5NO correctly, and run T5HO lamps at T5NO correctly. And sometimes a bit more than standard T5NO output.
The fixture can contribute to the issue as well. Fluorescent lamps, up to some point of failure, run better as they warm up. Right up to the point where the thermal cut out or breaker, cuts out.