Obsolete fluorescent light fittings

[broadgage]

As you have found, a 150 watt incandescent lamp will serve as a resistance ballast for a 40 watt tube.
Such an arrangement wont be very efficient though as the 240 volt 150 watt lamp will be badly underun.

Special ballast lamps used to be manufactured (for use with a starter, not with a starter built in)
AFAIR these were rated at about 160 volts and had a 3 pin BC base.

If selecting a substitute ballast lamp it takes some experiment to get the lamp current right.

[Hunts smoothing bomb]

the atlas ballast lamp is quite dim also when the tube is lit and lights up like a normal light bulb when the starter switch closes. I've measured the lamp current at 480mA with the original and 413mA with the 140w ballast made from a 100w & 40w bulb.

[Mr Moose]

Hello,

I have attached the entry for the Atlas Kitchenlight from a builder's merchants catalogue from the early 1960s

It says it has a 40w quickstart tube and a 70w combined starter/ballast lamp.

Interestingly 40w for the tube and 70w for the ballast make 110w total which is very close to the 113w your fitting takes.

Yours, Richard

[julie_m]

Just as a slight aside, when fluorescent tubes are given a "T" number, is this one-third of the diameter?

[Brigham]

Originally Posted by ajs_derby

Just as a slight aside, when fluorescent tubes are given a "T" number, is this one-third of the diameter?

It's the diameter in eighths.

[julie_m]

So it's 1 / 3.175 of the diameter, then. Close

[Herald1360]

Surely it's just 8 times the diameter in inches?

eg T12 = 1.5" (12/8)

Unless you're thinking in metric, of course

[Zelandeth]

Lee,

Lovely looking fitting that one! Seems to be very much a competitor to Mazda's Netaline which was a very similar product from about the same period.

That used a wire resistance though rather than a ballast lamp. Bit bitter-sweet for owners of them though given that ballast lamps are hard to find, but the ballast in the Netaline is asbestos sheathed.

The T prefix you see on the tube sizes is indeed the tube diameter in eighths of an inch, common sizes being T5, T8 and T12 (with some of the higher power tubes, particularly GE's Powergroove lamps which were never common in the UK and are virtually unknown nowadays being T17).

I believe the more modern tubes, measured in millimetres is shown with a dash in the middle, i.e. a 5mm diameter tube being shown as T-5.

[MrElectronicman]

Interesting thread, here's Wikipedia's comments on the sizes
http://en.wikipedia.org/wiki/Fluorescent_lamp_formats

I have been changing some of my fitting with electronic ballasts in order to accommodate the newer lamp types (T-8), as this type does not work well with the old transformer ballasts. I also checked the power consumption for both types of ballasts and it looks as if the electronic ballasts actually consume slightly more power

[Zelandeth]

The increasing scarcity of T12 lamps here is proving to be quite a problem, especially as their T8 equivalents won't work on some ballasts, notably quick-start examples (which will just sit there with the ends glowing forever). This came as somewhat of a surprise for the maintenance guys in a building I used to frequent which was lit entirely by 3x40W T12 and 3x 20W T12 quick start fittings, when they bought a pallet load of T8 replacements...then discovered they wouldn't work. Oops.

Funny, but I've been doing the opposite to MrElectronicman here over the last couple of months, converting electronic fixtures to switchstart magnetic for reliability reasons. i.e. I'm fed up of replacing ballasts more frequently than lamps.

I don't have any historic fluorescent fittings at present (well, got a couple in the van from the early 80s I guess), though I do have one Colour 740 80W BC Cryselco tube from 1970 which can be seen below.

Would love some time to pick up a fixture of the proper era for it to be shown in.

Also shown below for interest sake, rather older T5 lamps - one being from my old workplace, a couple of Coughtrie SBF16 bulkhead luminaries which were run 24/7 in the stairwells and are believed to be original to the building which opened in 1968. They're still going to this day, though not for much longer as the building is shortly to be demolished.

Final picture is one of the cabin lights in my van, a 13W T5, probably dating from the late 70s given that the van's from 1980.

Thought these might be of interest.

[bobbyball]

I have been reading this thread with interest as I also enjoy "vintage" flourescent fittings. My favourites are the circular types. I have an excellent example now mounted in my lounge with twin tubes - 32W and 40W. The chokes do "buzz" a bit and I had been investigating the possibility of converting them to electronic but haven't found any suitable types and in view of what has been said above I probably won't bother, may try mounting them on rubber pads or blocks, or simply turn the music up louder!

In the flats where I used to live we had the Coughtrie fittings - these had 3 x 8W tubes and if I remember 3 starters and 2 ballasts, a rather strange setup. As I was the only one vaguely "technical" there I used to keep them going although it could be a challenge getting all three tubes to work at once, bad contacts and the like.

My favourite linear lamps were the Thorn "Arrowslim" range, with of course the fitted diffusers, I could go on....

Best Regards

Robert Ball

[emeritus]

An old textbook said that the BC base for fluorescent lamps was adopted due to the need to get fluorescent lamps into production quickly to assist the war effort by improving the efficiency of factory lighting, and that production was concentrated on the 5' length. The IET library used to have a US-published reference book that gave details of the then-current fluorescent lamp types, some of which, like the "power groove", do not appear to have made much impact in Europe. There used to be "watchdog" starters that would stop operation if the lamp failed to start after a reasonable time, but they fell out of use with improvement in lamp reliablility.

I understand that the silicone coating of the outside of the lamps that is necessary for reliable operation in Europe due to the humid climate, is not normally needed in the US.

At home we are still using two 4' fittings that have the ballast at one end that were in our house when we moved in over 30 years ago. They have no starters, always start first time at full brightness and are absolutely silent. The modern skinny tubes don't work in them so in the light of the earlier comments I had better get some spares now.

When I refitted our kitchen with concealed fluorescents about 25 years ago I had to return my first purchases as they made a loud buzzing noise that I couldn't make go away, and since then have stressed the need for the lamps not to buzz when buying new ones. I haven't had any problems recently.

[Zelandeth]

Emeritus: Those starter-less fixtures you have there will be either quick start or series-resonant start. Good old fittings most likely, but as you've found they won't start T8 tubes due to the higher voltage requirement. I don't actually have any quick start fixtures here, though I'm currently trying to get hold of a few 3x20W T12 and 3x40W T12 quick start fixtures from the late 60s. These were in daily use since the opening of the building they're from in 1968 until July last year. We'll see how that goes. I'm not holding my breath, but if I do get some, info and photos will appear here.

Power Groove lamps are pretty much unknown here I think, in fact I don't think I've ever seen any T17 lamps over here, Power Groove or otherwise.

[Herald1360]

Originally Posted by emeritus

When I refitted our kitchen with concealed fluorescents about 25 years ago I had to return my first purchases as they made a loud buzzing noise that I couldn't make go away, and since then have stressed the need for the lamps not to buzz when buying new ones. I haven't had any problems recently.

I suspect that most modern fittings will now have electronic ballasts, certainly cheaper ones do. Whilst this may be a lifetime problem, they are silent (unless you're a bat?).

[emeritus]

Until I rewired, the old fluorescents were not earthed, but they always started OK.

I have some 5' double tube fluorescents that I bought as scrap in 1989 [ 10p each] when I was working for GEC when the luminaires on site were all being replaced by modern skinny tube equivalents. They have 2 pin connectors. The only problems I had were that some of the push-on terminals that made connection to the ballast, became brittle and disintegrated. I still use them in my garage and loft but have no idea when they were made. I have plenty of replacement tubes, also bought as scrap at a bargain price.

I have a book on lighting published in 1956 which tabulates the lamps then in use. It says that the 80W and 125W (5' and 8') lamps have B.C. fittings, while the smaller sizes have bi-pin caps. It also shows how to connect 15W, 20W and 40W lamps in series for a 240V AC supply without using a muliti-winding choke [they must both be of the same rating], but this requires the use of a 4 pin thermal starter that I presume is now obsolete: see attached PDF. For DC operation it says that a choke is still needed for starting, and the value of series resistance is 165 Ohms for either a single 80W lamp or two 40W lamps in series, double this for a single 40W lamp. Alternatively an under-run 70W tungsten lamp can be used for a single 40W tube The need to periodically reverse polarity is mentioned.

I believe that the first generation of fluourescent lamps used on Britsh Rail passenger coaches ran on DC and used the special switches that reverse the polarity on alternate operations to address the polarisation issue. I recall that the second generation used invertors that were prone to emit highly annoying high frequency noise!

[Brigham]

I've never seen a sub-5' tube with bayonet caps, so that certainly rings true. The 4-pin thermal starter can easily be replaced by a glow-tube type. They are electrically similar; the heater for the bimetal breaker simply being an inert gas instead of a glowing coil.

If you look inside the can of a 'later' 4-pin starter, you will often find a modern-type glow-tube, and a shorting link. You can tell from the way the lamp starts whether the newer type has been fitted.

[Hunts smoothing bomb]

Originally Posted by emeritus

An old textbook said that the BC base for fluorescent lamps was adopted due to the need to get fluorescent lamps into production quickly to assist the war effort by improving the efficiency of factory lighting, and that production was concentrated on the 5' length.

This is true, the need for better efficient lighting in factories was sought during the war effort, by the 1930's mercury street lighting began to appear in large towns and cities using 80w and 125w MA lamps, as the war came upon us better lighting was needed in factories (probably for production lines and the like) we decided to introduce the fluorescent tube as cheaply as we could as not to choke (no pun intended!) progress.

The UK decided to design two tubes that would run from the existing 80w and 125w MA ballasts, they would also use the current B22d caps fitted to GLS lamps. The 80w tube was 5' long and the 125w was 8' long, by doing this money didn't need to be used for new expensive machinary to manufacture tube endcaps and newly designed ballasts.

I believe the bayonet capped tubes were produced right up until the late 1980's, possibly the early 90's.

Cheers

[broadgage]

RE post 175,
A pair of 4 foot, 40 watt lamps can not be operated in series from any common type of ballast. I believe that the reference to 40 watt lamps in series pairs refers to the less common 2 foot 40 watt lamps, these can certainly be operated two in series from an 80 watt ballast. If wanting to do this these days you will have trouble locating the correct starters, thermal ones are no longer made, and glow starters for series pairs of 2 foot 40 watt lamps are hard to find. Glow starters intended for series pairs of 18 watt lamps are readily available and will work but tend to have a short life on pairs of 2 foot 40 watt lamps.

[emeritus]

Broadgage is indeed correct. Elsewhere in the chapter it is explicitly stated that

"Lamps of 15-, 20-, and 40-watt ratings (the last in the 2-ft length only) can be operated two in series on 200 to 250 volts provided that the lamps are of the same rating",

and that the power factor can be improved from 0.5 lagging to 0.85 to 0.9 lagging by using a capacitor across the mains of 7.5uf for a single 80W or two of the 2ft 40W lamps in series, and 3.2uf for a single 4ft 40W lamp.

PDF of the table of the lamp types of 1956 attached. The 15W, 20W and 2ft 40W lamps seem to have been intended for series operation as the choke loss is only stated for this usage. It is mentioned that the table only lists the most important types, and nothing is said about the less-important types.

I took the covers of one of my 4ft fittings last night and they were made by Crompton Parkinson. The ballast is marked Quick Start.

[ex 2 Base]

Atlas used to give away free booklet to "Tec" college electrical installation students and there was a multitude od circuits in them plus other usful info. Ships had florescent lamps operating on 220 volt DC and they had rotary polarity reversing switches fitted. otherwise the tube ends went black.In the booklet there was circuit details regarding dimming florescent lamps, a small transformer was contained in the box together with a multi contact rotary switch.the transformer kept the tube heaters working all the time.We fiitted them into railway signal boxes.ted