Can you interchangeably use 36 Watt and 32 Watt F32T8 tubes? Some are only available in 36 Watts, but I want to run them on a 32 Watt ballast. Can I do this?

36W T8 have the same lamp current and voltage as F40T12 so they can operate on F40T12 preheat ballasts, but they have krypton buffer which have higher starting and restarting voltage, so they won't start on rapid-start or preheat with OCV less than 230V. The brightness of both 36W T8 and F40T12 is the same.
F32T8, have different lamp current and voltage than F40T12, so they aren't interchangeabe to each other, but they use argon filling with low starting and restarting voltage, so rapidstarts can be designed for them, and they are brighter and so more efficient than 36W T8.
So 36W T8 can't operate on F32T8 ballast and the opposite.

I am talking about electronic ballasts, Instant Start and Programmed Start.
Does that make a difference?

Basically assume that the same will happen as if you put a F40T12 on the same ballast, as F36T8 and F40T12 are similar

Basically assume that the same will happen as if you put a F40T12 on the same ballast, as F36T8 and F40T12 are similar

So if the ballast can run F40, it can run F36.

Electronic ballasts yep, i dont expect starting problems with them

Preheat can run 36W too, that is what they were designed for in the 1st place

Rapid Start - Over here some RS ballasts manage to start them fine, but it is not predictable or reliable. Dont know what will happen on US Rapid Start (that have same starting type but otherwise are completely different in construction)

Then why have F36T8? Why not use F32T8?

It can be used directly in place of F40T12 on most European Magnetic gear (except Rapid Start), and it can be powered by Electronic ballasts at 32W (but those are ballasts made for the F36T8, not for the US F32T8). So one lamp both for Magnetic and Electronic

It can be used directly in place of F40T12 on most European Magnetic gear (except Rapid Start), and it can be powered by Electronic ballasts at 32W (but those are ballasts made for the F36T8, not for the US F32T8). So one lamp both for Magnetic and Electronic

So they are more or less interchangeable.

Then why have F36T8? Why not use F32T8?

F36T8 (rated for 0.43A, arc voltage about 95V; the F40T12 is 0.43A, around 105V) is electrically compatible (at least partially; they need higher voltage for ignition) with the F40T12, so it can run in fixtures still equipped with an F40T12 ballast (provided it gives off enough voltage for ignition - so preheats or I most electronic). Fixture equipped with F36T8 ballast can run either the F36T8 and the former F40T12, so these lamps could be altered freely.

F32T8 (rated for 0.25A, arc voltage about 140V) is electrically completely different lamp, so although it is of the same physical size, it can be run only in fixtures, where the ballast was replaced for this type. A fixture equipped for F32T8 then can not run the F40T12.

Quote from: wattMaster on July 16, 2016, 01:32:45 PM

Then why have F36T8? Why not use F32T8?

F36T8 (rated for 0.43A, arc voltage about 95V; the F40T12 is 0.43A, around 105V) is electrically compatible (at least partially; they need higher voltage for ignition) with the F40T12, so it can run in fixtures still equipped with an F40T12 ballast (provided it gives off enough voltage for ignition - so preheats or I most electronic). Fixture equipped with F36T8 ballast can run either the F36T8 and the former F40T12, so these lamps could be altered freely.

F32T8 (rated for 0.25A, arc voltage about 140V) is electrically completely different lamp, so although it is of the same physical size, it can be run only in fixtures, where the ballast was replaced for this type. A fixture equipped for F32T8 then can not run the F40T12.

So running F36T8 in a F32T8 fixture will underdrive it.

So running F36T8 in a F32T8 fixture will underdrive it.

Well, depends how the ballast will respond to seeing 95V instead of 140V arc.
But indeed, I would expect the lamp being underdriven and the ballast to overheat.

why ballast to overheat ? Is lower arc V problem for common Electronic FL ballasts ?

why ballast to overheat ? Is lower arc V problem for common Electronic FL ballasts ?

It could be. Depends on how is the ballast designed. Some feed really constant current, there it won't be of any problem.
But some use rather low OCV (they just boost that only for ignition) and drop very little on the ballasting inductor, counting on the specified arc voltage (on HF you do not need the OCV for reignition spikes as you do on 50/60Hz). There the output current may become increased and that may overheat the coil and maybe even the output transistors. The problem with electronic is, you never know what is inside. Even the same maker may change the concept without any warning, even keeping the same part number. And what had worked suddenly becomes a problem.

Something was not mentioned here: F36T8s have 9V preheat cathodes..that's also why they don't work well on Rs in the US