A very quick & possibly inaccurate bit of research reveals these 14w T12 run at 0.37A. The ballast here has a rated current of 0.47A. The numbers no add up!

Looks like their multi wattage PL chokes?

Yeah thought as much. What would these be good with?

Going off the print, looks like PL upto 11watts, and it's also got 2D sizes on there?

Well that's lowsy. I guess i'll keep a look out for some PL's to run with them then. Didn't think they'd be any good for my tubes anyway but now i've got some spare ballasts so nothing's lost.

They are fairly wide range for PL. Looks like they are really centered around 18W PL-C / 16W 2D and will overpower everything below that

See plenty of those in charity shops. Looks like I can finally start collecting them too.

these chokes give a lamp current of 0.21A the 0.47 is something else. as such tho these would under-run a F14T12 quite badly. you would be much better off running an F14T12 on an F15T8 choke

just run them of 15 watt T8/T12 chokes like ive said. it how it been Running here in USA. have not made dedicated chokes since 1950s. it the norm to use 14- 20 watt choke here in the USA. Listen to Lightbulbfun as I have sent him
F14T12 lamps.

that screw ball .47 Amp ballast would be interesting to use on American 34 watt T12.

λ is power factor

The use of 14..20W ballast for 14..20W lamps is affected by voltage. At first approximation (disregarding ballast coil resistance, lamp power factor, etc), ballast and lamp behave as :

V(lamp arc)^2 + V(ballast drop out)^2 = V(line voltage)

I = V(ballast drop out) / X

Where X is the ballast impedance, which is defined by its structure (number of turns, core dimensions, etc). If we disregard effects like saturation, then X is constant for each ballast

When we put different lamps with the ballast, we change V(lamp arc), it is generally lower the shorter the lamp is. Therefore, V(ballast drop out) changes accordingly

But by how much ?

Compared to 120V, the change of few 10's volts in lamp arc voltage is more significant. Lower voltage lamp put on "20W T12" ballast will increase the voltage dropped on the ballast, and therefore its current, so the ballast will supply higher current to a lower voltage lamp

Compared to 230V, the change in lamp arc voltage is less significant, (due to the voltage drops being out of phase, the change in ballast drop out voltage is even further less significant). So the ballast will put out current closer to that with the first lamp. I.e. the increase in current will be less

This change in current does happen on 230V with lamps with higher arc voltages (which are more on the same scale as the supplied 230V), thats how 20W T12 ballast can supply 370mA with 20W lamp and as low as 320mA with a high voltage PL of 24..26W

I've got a 30wT12 or 2x15w ballast for these T12 tubes of mine. Good luck finding 14/15W magnetic gear anywhere for under a fiver. When I ordered these I didn't think to check the rating. I just saw they were £2 and though fuck it. For £2 a few of these'd find a use and if they do my T12's then great but if not I could power plenty of smaller lamps in the future. I always see PL and 2D fluorescents in charity shops cheaply and now I can start buying them as I have some gear that'd be good with them.

use the 30 watt T12 chokes with 2 lamps in series. This about only lamp in USA that ran two lamps in series on manual push button start.

An 18/20w T8/12 choke runs a 15w T8/12 very close to spec, so would probably run your 14w T12 well enough

And yes now I look at the picture closer I see the 0.47 is actually the power factor, doh!