I just bought a ballast from Ebay a couple minutes ago, and I noticed that the ballast amps are lower than
the amps on the ballast I'm replacing. Does this mean that I should expect dimmer light?
Reason why I ask... I've got two 0 degree HPF trigger start ballasts made by Advance... their amps are 0.23.
Lamps with those ballasts run weak, and the light output is slightly brighter than with LPF trigger start
ballasts. I've replaced them with 0 degree HPF trigger start ballasts made by GE... Bonus Line. 0.32 amps.
The lamps run much brighter/stronger. No noticeable flickering.
Now... the ballast I'm buying is meant for PL lamps... 18 watts. So I'm assuming the ballast should run T8
or T12 15 watt lamps just fine. It is also HPF, but it supposedly only runs at 0.23 amps. Should I expect
dimmer light from this ballast as well? Also, should it have a higher filament voltage, much like trigger start?

This thread will be deleted once I come up with a feasible conclusion, based on your answers.
Thanks guys

Power in = V * I * PF

Power out (of ballast) = Lamp brightness



At first lets disregard ballast losses completely. If so, V * I * PF = Lamp brightness

If a ballast have lower I, same V and PF - lamp will be dimmer

If a ballast have lower I, same V, but higher PF - that would depend on how V * I * PF actually compare. Not all HPF ballasts are necessarily equal, one might be PF 0.9 and one be PF 0.99

If a ballast have lower I, higher V (say, one rated 110V and one 125V) - that means that it is meant to draw lower current at its rated higher voltage. What will happen if you power it with not as high voltage ?

 - Magnetic ballasts will tend to lower I with lower V, so underdrive the lamp three fold : Once due to the lower rated I to begin with, Then due to the even lower than rated I resulting from the lower supply voltage, and then due to the lower voltage too

 - Electronic ballasts vary. Some will behave similarly to the magnetic, some others will actually increase the current at lower supply voltage, so might drive the lamp just the same



If then we look at ballast losses too, then the difference in ratings might also be attributed to that. For example, one ballast have higher V * I * PF, so higher input power, but happens to be more lossy, so the output power could be the same or less than the other ballast



PL-C 18W ballast is good only for PL-C

PL-L 18W ballast is good for :

 - Magnetic is good for 18W/20W T8/T12. With 120V ballast thats about it. With 230V ballast, it is also good for several other lamps

 - Electronic - usually 18W PL-L ballasts are also rated for 24W PL-L and maybe other sizes, and then they can drive also T5HO of the same wattages as the PL-L

15W lamp is of lower arc voltage than 18W, so not necessarily suitable for all ballasts. If its magnetic, see how much it heats