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Discuss Metal Halide lighting in the Electrical Forum area at ElectriciansForums.net

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Regular EF Member
Hi all,

I posted this earlier under a different title and unfortunately didn't get any response. So apologies if you have already seen this.

I need to design light solution for public hall, which is current lit using 35 x 60W Par lamps and this is not sufficient. I was considering metal halide lamp, but having never used them was wondering what peoples thoughts where on their suitability. Criteria form lighting is energy efficient and dimmable. Roof is upto 22ft.

From a technical point of view, how easy are they to dim?



Electrician's Arms
I love them. They are actually quite efficient (24%) i seem to recall or thereabouts. Which is pretty good. No where near LED ! Nasties in bulb (vapoirised mercury) so watch out for that. As for the light given, think its top.

Take a while to warm up so crap for security lighting on sensor. Fitted some (green one & orange) for a neighbour in garden, looks like eurodosney when you drive past!
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Regular EF Member
Apparently you can dim metal halide lighting, but I think you need electronic ballasts in them.
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Regular EF Member
You can dim them with a ballast. I just never done it, so I am looking to see if anyone has had any experience with this. I've used phase width modulating device before to dim tubes and had mixed results. The more I read about metal halide the more I am going of the idea, because of environmental factors.

Anyone can think of a viable energy efficient dimmerable solution it would be apprecriated. Main issue is ceiling height, as I'm sure installing dimmable CFL will make matters worse.


Scouser and Proud of It
Respected Member
check with meteor ( forum sponsors ) see if they do any high lumen, dimmable LED lighting.


Forum Mentor
I've not used metal halide. Just trying to get a feel for them; what rating of metal halide would be comparable with an ordinary 500W linear halogen floodlight? And how long do they take to get to full brightness from switch on?


Electrician's Arms
70W Metal Halide far outperforms 500W R7s halogen.
I like the crisper white of the 4000K lamps, compared to the 3000K, versus 2700K for the halogen.
Circuit load roughly 100W for 70W fitting with magnetic ballast.
But you've got 12uF of PFC capacitor in each one of those, so allow plenty of margin (3x Lamp watts) on any switchgear or contactor
At a rough guess, it takes just under 2 mins for something like full brightness... but the first 30 secs or so there's next to nothing.

Only downside, UV light output. Many lamps now have some UV-stop properties. Or sometimes the fitting safety glass will have a UV-stop coating. Just something to beware of if there's paintings hung in there etc

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We have slowly been replacing a load of high bay metal halides with linergy fittings. The light output is really good and they're a lot more energy efficient. They do either a four or six tube option and although I don't think they can be dimmed, they can be wired so that they can be switched in groups of two tubes if required.

Editted to add, they are damn expensive though, think it's about £200+ for the six tube fitting.
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