Hi all, I know that the forum describes post-1980 as modern, but as this 1981 lamp is no longer made and is significantly different in design from current SOX lamps, I feel it belongs here.

My question is this. I have just acquired a lovely 18W GEC Super SOX lamp from March 1981 and reading the leaflet that comes with it (see below) it states that the burning positions of ALL ratings of SOX lamps is ± 20° of horizontal, including vertically cap up.

Since I have always understood this to only apply to the lower wattages (up to 55W) I was surprised to read that this apparently applies to ALL ratings, including the 135W and 180W lamps  

I am not sure I would want to run a 180W lamp vertically, has anyone ever done this and if so, how did the lamp react..?

I can only see it being a problem for Philips lamps, because of the shear amount of sodium their filled with?, but GECs Shaw made lamps only had it in the U bend, and as long as it was properly supported I don’t see how running a 180 vertical would significantly hurt it?
Not that anyone would have a reason to run a 180 vertical though 

I can only see it being a problem for Philips lamps, because of the shear amount of sodium their filled with?, but GECs Shaw made lamps only had it in the U bend, and as long as it was properly supported I don’t see how running a 180 vertical would significantly hurt it?
Not that anyone would have a reason to run a 180 vertical though 

You won't get me trying it..! Mind you I'd have to get a 180W lamp first 

I'd love to light a hallway with vertically mounted 180 watt Sox lamps internally built into pillars in the walls.

Probably would be blindingly bright but the effect is probably cool.

For the most part you would have to support it’s weight on the dome end so as to not pull the BC cap or its pins off!

For the most part you would have to support it’s weight on the dome end so as to not pull the BC cap or its pins off!

Indeed. As an aside, why were SOX lamps always made with virtually standard BC caps..? The BY22d version used for the majority of LPS is marginally different, with the extra piece between the cap contacts (which is, I believe, to help with the prevention of high ignition voltage jumping between the terminals) but it's essentially a domestic lamp cap. The vast majority of discharge lamps other than SOX (with the historical exception of some of the lower wattage mercury lamps which used the 3-pin BC cap) use either E26/27 or E39/40 caps. Why don't SOX lamps use these..?

Indeed. As an aside, why were SOX lamps always made with virtually standard BC caps..? The BY22d version used for the majority of LPS is marginally different, with the extra piece between the cap contacts (which is, I believe, to help with the prevention of high ignition voltage jumping between the terminals) but it's essentially a domestic lamp cap. The vast majority of discharge lamps other than SOX (with the historical exception of some of the lower wattage mercury lamps which used the 3-pin BC cap) use either E26/27 or E39/40 caps. Why don't SOX lamps use these..?

Probably because you want to have assured lamp positioning in the fixture.

Probably because you want to have assured lamp positioning in the fixture.

Possibly, but the 3-pin BC cap has been used in the past for some lamps that need this. I have a projector lamp that uses one (see picture).

There are screw caps with locator devices on them that could be used. For a vertically positioned lamp, especially a big one, I would much prefer some form of screw cap to a bayonet one.

The 3pin B22d cap was introduced for mercury lamps because they would be destroyed if accidentally installed in a 230V mains lampholder for ordinary bayonet incandescent lamps.  However until the advent of the 2nd generation SOX 18W with an internal capacitor to allow use in USA, other LPS lamps do not strike if installed on the mains supply.  So there was limited risk of the arc striking on the mains, and no need for the unusual 3-pin caps.  Moreover the luminous intensity distribution of SOX lamps is symmetrical around a 180d plane, so it makes more sense to use a lamp cap having that same mechanical symmetry.

Thanks, James. Is it really possible to run the big 135W and 180W lamps vertically, though..? It seems a bit risky to me, I'm certainly not about to try it