After trying to get a couple of SOX lamps to work and then poking around here for a while, I have questions about SOX and ballasts (and about ballasts in general, which really should be called "bafflists" I believe). As a starting point, I've been trying to understand the logic of the Fulham line, and have even pored over some of their documents to get a clue.

What's the best fit for the SOX lamps? How many reds go to which lamps? And so on.

This PDF helpfully lists the lamp arc current for fluorescents, and corresponding Fulham ballast model and wiring:
https://www.fulham.com/PDFs/SunHorse-UV-Flyer.pdf

Thinking of my 55W SOX lamp which is dim on the WH3, I looked for arc current close to 0.6 amp, which I think matches that light.

Of all the fluorescent gin joints listed in that PDF, only 3 lamps came really close to that. And for those they list the WH8 with 2 reds for each of the 0.59 or 0.6 amp lamps.

So is lamp current the secret of these red wires? And if so, is there a spec for Fulham ballasts of the amp/reds for each of their offerings? For the WH8 it looks like 0.3 amp per each of the 6 reds for example (but more like a range probably, with some overlapping).

Also, I notice most of the off-label ballast prescriptions mentioned here are for Fulham Co, Inc. But is there anything special about the their line, i.e., that Philips or GE Current etc. don't have (maybe cheaper than the 2 ft long WH8)?

I also love poking around in musty textbooks - so don't hesitate to send me to one of those if that would help me.

Thanks!

I'm afraid I am not really well up on running SOX in the US, I don't currently have any of those Fulham ballasts but I'm considering getting one or two to play with, though.

I like "bafflists" though, I think we should all adopt that word forthwith 

The Fulham "WorkHorse" ballasts are quite adaptable. They do a fine job on SOX lamps. But you need to select the right model and number of red wires to light them properly. For example, 35w & 55w SOX lamps can be lit nearly to full light with the WH3 but the ballast is at maximum output. Better to use the WH5 with 2 reds together, still under-driving by a bit. 3 reds from WH5 & 55w SOX is quite good.

Some tests can be found here: https://www.lighting-gallery.net/gallery/thumbnails.php?album=3893

The Fulham "WorkHorse" ballasts are quite adaptable. They do a fine job on SOX lamps. But you need to select the right model and number of red wires to light them properly. For a exampl, 35w & 55w SOX lamps can be lit nearly to full light with a WH3 but the ballast is at maximum output. Better to use the WH5 with 2 reds together, still under-driving by a bit.

Some tests can be found here: https://www.lighting-gallery.net/gallery/thumbnails.php?album=3893

I did read about your tests showing that the WH5 underdrives the 55w SOX bulbs a little, as well as your nice reports on other SOX/ballast combinations. Very helpful!

So In the spirit of experimentation, I was looking to see what possible configuration among all the other Fulham ballasts might be better than the WH5. Comparing a bunch of lamps and their wiring charts, I discovered that the WH8 with 2 reds seemed closest to the current and watts of the WH5 with 2 reds, but slightly higher.

I did also find a fluorescent bulb with a 600 mA lamp (TUV25W G25T8) input spec, same as the SOX 55w lamp (which is pretty rare since most T12s are 430 mA and T8s are 265 mA). The Fulham site shows that the WH8 ballast would drive 3 of those with two red wires each.  But that’s a big ballast, would it send more current if you just had one lamp attached to 2 reds?

OK - So I sent a question to Fulham tech support to see how the input current would be affected if you used that ballast to drive just one or two of those lamps, assuming that each 2-wire pair would still draw about the same current. But that’s not quite the way it works. Here’s the reply from Fulham:

“The lamp is rated for 580mA. Using wiring diagram #17 [2 reds to one 25w UV lamp] will result in 860mA going to a single lamp, and wiring diagram #23 [2 reds each to two 25w UV lamps] will result in 680mA.
It would be better to use wiring diagram #16 [1 red] for one lamp. It will output 525ma which will underdrive the lamp slightly by about 10%. We will not have any additional wiring diagrams for 2 lamps.”

Looks to me like the total draw of one 55w SOX might reduce the current output compared to a single 25w T8 lamp on 2 reds, and maybe overdrive the SOX lamp a little. What do you think — worth a try? What do you recommend to reduce risk of blowing the SOX bulb? Should I monitor the system input watts and pull the plug if it goes too high? If so, what is the max startup wattage normally for the 55w during warmup? I believe these may drift up quite a bit before settling down to their rated wattage, right? And what do we think the ideal full output (warmed up) wattage would be for this lamp and ballast?

Thanks again for all the good info!

If you're running a lamp on a ballast that wasn't designed for it or vice versa, always keep a close eye on both lamp voltage and current. In the case of discharge lamps, it is the current which is the critical factor. For a 35W or 55W SOX lamp that is 0.6A or 600mA depending on how you want to say it. A clamp meter is the best option for current measurement, as it doesn't require interruption of the circuit and you won't subject a multimeter or whatever to the ignition pulse. A multimeter is of course perfectly satisfactory for measuring lamp operating voltage, but wait until the lamp has started before you apply it to the circuit.

As the lamp warms up, the voltage across it first rises and then starts to fall. After the lamp is fully run up, for a 55W lamp you should see 0.6A and a lamp voltage of around 109V.