After I have been noticing that I have a very fond liking for Japan’s diverse selection of HID retrofit lamps for mercury vapor ballasts, I am wondering what favorite mercury retrofit HID lamps other collectors like.

Israel, we use European spec lamps

Over here Mercury retrofit lamps are not a thing, and have not been a thing ever. Mercury installs stayed Mercury as long as they were not fully replaced with new luminaires. Occasionally existing luminaires were refitted with new gear to run a new lamp type

With this way of things, the closest thing would be running a MH lamp (a non retrofit type) in an existing luminaire with the addition of an ignitor

This could work for 400W. It does not work for all wattages (European MH up to 250W follow HPS spec, so would still not match a Mercury ballast)

400W had been the most common wattage for MH lamps in MH (from the start) luminaires over the last 20+ years. However, back when Mercury lighting was being installed, 125-250 Mercury were the most common wattages. So this limits the 400W retrofit option to the fewer 400W Mercury luminaires out there

For some small road lanterns which used 80W Mercury, 70W HPS with internal starter have been sometimes fitted right on the existing Mercury gear. It does light up, but its not the correct lamp for it and it does not work properly



In fact i have seen much more of the opposite, when Mercury lamps of 125W have been used to retrofit 100W MH luminaires (with, and possibly also without remioving the ignitor) - Mostly due to the lower cost of the lamp itself, in places where the reduced light was not too noticeable

This is quite a close match and the Mercury lamp seems to work well on the 100W ballast. (Which is for HPS and HPS-spec MH)

The fact it was used specifically to replace MH and not so much HPS is due to the socket. Over here 100W MH were mostly American lamps with E26 base (screwed into ordinary E27 sockets) to which also the 125W Merc could be fitted, while HPS used E40 sockets, despite all the rest of the gear being the same

A correction: In fact, most modern (1980+) European 400W MH lamps were made for HPS impedance ballasts too, Osram, BLV. Philips being a bit outlier with their dual-standard lamps running on mercury gear better.

   

@RRK, do you have any preferences for any self-starting mercury vapor retrofit HID lamps that do not require external ignitors?

Examples include the Philips HPI BUS lamps and the Philips SON H lamps.

Honestly, specific self-start mercury retrofit lamps are practically non-existent in my part of the world. Mercury fixtures either still continue to run mercury, or get replaced in a whole to HPS or today LED.  There was a lot of Chinese 3-electrode MH lamps in 250/400W in Kazakhstan, colored and white, but these were probably made for American standard and in practice require elevated OCV or at least a soft ignitor to start reliably.

It is not only because I was involved in parts of its development, that I would have to go for the Sylvania Relumina ceramic metal halide lamps.  They offer the greatest energy saving, highest luminous efficacy, longest life, whitest light and best colour rendering of any of the mercury retrofit lamps ever developed, and without the usual drawback of producing far more light than the mercury originals and leading to glare or wasteful over-illumination.  This was made possible by employing a small inductive ballast to reduce the lamp power.

As a close second I would have to go with its little-known predecessor, the Sylvania SHX-S sodium retrofit that also employed an integral ballast coil to enable that 85W sodium lamp to replace 125W mercury.

But in terms of technical elegance I think the Iwasaki Sunlux Ultra Ace with FEC and Sidac ignitor is probably one of the most ingenious.  That delivers much higher efficacy than typical sodium retrofits due to its xenon-filled arc tube, and the unsaturated vapour design ensures a significant improvement in electrical performance and life.