I assume you are referring to the 4ft F25T12. The reason that lamp can’t be used on commercial ballasts has nothing to do with the capacitor or the ballast itself. The “F25T12” is nothing more than a regular F40T12 with weaker electrodes that can’t handle as much power. It’s a F40 that is designed to be underpowered. This renders it incompatible with commercial ballasts which are usually “normal ballast factor” (operate lamps at their rated power). The F25T12 would operate at 40W in this configuration, causing early failure. Residential ballasts are usually “low ballast factor,” and typically operate F40T12 lamps at 25W or less, meaning the F25T12 gets its designed power and will last its rated life.

F40T12 34W lamps will cause any ballast to run warmer, residential or commercial. In fact, earlier residential ballasts were known to get unbelievably hot with energy-saving lamps. I believe this is because the 34W lamps cause actually draw more power on LPF ballasts than 40W lamps do, which causes the ballast to operate well above its rated power and temperature. Later models like the Advance HB-234-TP were designed to handle 34W lamps better, but you should never run a 34W F40 on any residential ballast that does not say it is compatible with one. Same goes for HPF  commercial ballasts. Many units from before the 1980s were not designed for energy-saving lamps and would overheat with them, so just check your ballast before installing them. Newer ones are usually OK with them.

An ad in the April 1940 edition of the American City Magazine is interesting. General Electric details how the City of Niagara Falls “ Had one of the finest luminous arc street lighting systems, yet it recently relighted 23 miles of street for better night traffic safety. More than 1000 arc lamps were replaced with modern efficient incandescent luminaires”. There is a photo of the GE Form 81 luminaire. So arc lighting existed into the 1940’s.

"efficient incandescent" LOLOLOLOLOLOLOL

@RRK
Right... activation. Forgot about that part. Makes sense.

A sheet of metal will definitely protect you, but it is not very convenient to walk around an already chaotic situation with a non-transparent sheet of metal in front of you.

With the technology sorted up well, feed-through reliability is not a major problem

Some reasons at least:

Manufacturing process certainly requires filament heating at some times for activation.

Two points is needed to support a beehive filament.

Two leads at each end are more mechanically robust. 

I believe that early positive column AC LPS lamps (like the Philora DA) had filament electrodes that were preheated before use, and possibly continuously heated during use. This obviously means that there had to be four feed throughs, two for each filament. Just like a fluorescent tube. No problem here.

But after after the Philora DO came out, they started instant starting the lamps. And this remained the case throughout SO, SOI, SOX, and SOX-E. But they never switched to one feed through per electrode, they always kept both lead wires. Looking at the construction of any modern LPS lamp, you can see that the two lead wires on each end are just connected together on the outside, rendering them practically useless.

Feed throughs are the one weak point, right? Wouldn't you want to minimize the amount of them that you have? Why not just have one wire feed through and attach the beehive cathode right to it instead of splitting it across two possibly problematic feed throughs?

Tested, cleaned, and serviced a number of 1987-1988 Lithonia Lighting 2xF40T12 fluorescent strip lights so that I can install them in the lighting workshop next weekend. The fixtures were acquired from FaceBook MarketPlace back in November.

The fixtures have a mix of ballasts, mostly Universal 446-LR-TC-Ps, a couple Advance R-2S40-TPs, and one has a GE electronic ballast which will likely be replaced. One fixture did not come with a ballast. All ballasts seem to work just fine, so I will go ahead and install the fixtures. A couple of lampholders needed to be replaced.

For cleaning, I disassembled the fixtures and pressure washed the housings, then I went back in with some wipes and put the fixtures back together. Took several hours to get them all done, but I’m glad they are all finished now. There is some rust on a few of the fixtures, but I won’t worry about that for the time being.

Yeah, a metal shield might protect you. A new 21st century use for medieval technology. 

@Ash I have seen pictures of those! They are super cool. I think that with modern materials (maybe using some sort of high temp FRP instead of ceramic) the fuse pin could be made practical, but it's way too late now. I would love to see this kind of design reincarnated but we have too many plug designs already, so whatever.

Interesting wattage comparison of different homes around the world, I didn't realize that modern 200A homes were so much more power hungry than others around the world. Also, homes in Israel have three phase? Man, that must be nice!

The problem is not only the fuse tube material

Plugs and sockets are designed to last for lots of plug/unplug cycles. The plug pins are fixed in the plug by having a large interlocking shape. No crimping

In any fuse of a more or less typical construction with crimped caps, the caps will be getting loose and coming off if it is taken in/out of the holder so many times



New houses and flats are now getting mostly as standard 3x25A, with the main cable of 10mm2 ready for 3x40A upgrade

Single phase connections for 1x25A and 1x40A are still available to order, but i think the main users for them nowadays are traffic lights, amenities in public spaces (like a ticket machine in a bus stop), remote metering/networking equipment clusters etc, not houses

In the 90s you would usually get 1x40A from the contractor in a new house, but the conductors for 2 other phases are already there for 3x40A. So a main breaker & busbar swap in your board, meter swap in the meter cabinet, and you have 3 phases

Before that in private houses you could get 3 phases at least as far back as 70s, in flats it was rarely more than 1x25

In villages often the private small farm was feeding from the house (with an underground or an overhead), so people were geting 3x25, 3x40 or more for having it in the ranch, the house just benefited from it on the way. Nowadays many of those village farms are getting upgraded with 3x100A and higher connections to support grid-tied solar installations on the farm buildings, so either freeing up the old service connection completely for the house use, or backfeeding through it from the farm to the house (with the old service drop to the house removed)

Yeah, that's why it is best to just either go and pick it up or find them locally.