Hello everyone!  Since I have picked up my new multimeter, I have been messing with all my preheat ballasts for my F14T12 to F20T12 lamps.  However, I went to GE's and Sylvania's website trying to find what is the "recommeneded" current for lamps and so far I have struck out.  The only one that I know is that F40T12 lamps are typically 430mA.  I am wondering what the current would be for F14T12, F15T12 and F20T12.  Any  help would certainly be appreciated since I am trying to use certain ballasts for certain lamps kinda like matching them up. 

Yeah, it's hard to find voltage and current info for a lot of fluorescent lamps. GE used to have quite a bit of that information on their site, but I can find it for very few lamps now. If you can find the arc voltage of a particular lamp, then you can determine the approximate full-power current by dividing the power by said voltage.

All three lamps are rated for around 0.38A.

You have to count for the power factor, which is around 0.9 (ideally 2*sqrt(2)/Pi), given by the current vs voltage shape mismatch: Current is rated as sinewave, voltage is always (at the mains frequency) near rectangular.

Oh...! That must be why arc voltage x current always seems to add up to slightly more than the power rating? Makes sense.

Oh...! That must be why arc voltage x current always seems to add up to slightly more than the power rating? Makes sense.

It is exactly the power factor. Some lamps tend to create higher reignition spikes (after the current zero cross the voltage tend to rise higher before the ionization is reestablished), what makes the shape mismatch worse, so with real lamps the power factor vary between 0.8 (more spiky voltage)..0.9 (smooth rectangle).

Without getting in the topic of power factor and current crest factor and all that, F14s/F15s/F20s usually run at somewhere between 350mA and 380mA. In fact if you're running those on a preheat choke, its current rating gives a rough approximation of lamp's current, though it may vary depending of the lamp wattage. It seems the longer the lamp, the less current the ballast gives.

These preheat ballasts run most of the lamps quite far off the rated current (usually bellow; the F20T12 barely at 15W,...), so you can not take those figures as the real lamp rated currents.
But the line current is there indeed the same as the lamp arc current.

i know most t5 are 160ma in preheaters.13w pl are 300ma
iirc 14-15w are 350ma
20w are 380.
it would be nice to create a db of all this including modern stuff.

From OSRAM you could download the complete catalog, for some lamps listing rated current even for both HF and mains operations (the HF operation causes higher PF, as the ionization can not change as quickly to follow the current, so the lamp behave more like a resistor)