Can LED light bulbs be a direct replacement for Metal-Halides?

Factual Questions
1

I’m trying to lower my company’s energy usage and they have been pushing for LED lighting for a while now. The biggest improvements will be on the parking lot lights but that is a professional job. Right outside the front door we have a canopy with M90 100W MG lamps in a can light fixture. Can I simply replace these with LED bulbs? or is there some goofy starter mechanism/ballast that these MH lights operate on?

If its an easy replacement, can anybody recommend a good LED bulb?

Also I don’t know what voltage this circuit is on. My supervisor thinks they are 277V though, and from my research it looks as though there are many lights that can operate between 100v and 277. I’m about to look through the buildings electrical drawings. (Not fully sure how to do this so there will be a learning curve!)

2

Main issue, the MH gas discharge lamp is very efficient at making light, and so what is the point of switching to LED ? How many lumens per watt is the MH lamp ? 100 lm/Watt. How many lumens per Watt from a dodgy retrofit LED lamp ? 80 ?
There is no point in changing a professional gas discharge lamp to LED on efficiency grounds !
see

You aren’t changing your outside lighting,

Its only the simple incandescent, halogen lamps that are too inefficient, and need to be changed. Your floury T8’s are also similar efficiency to LED, why bother…
And yes the MH lamp base contains a ‘ballast’ (to keep the light upright ?hehe) . That circuit would have to be removed to drive any other lamp type.

3

Metal Halide lamps are only 100L/W efficient in the most optimistic scenario. On the other hand, LEDs are easily 100 L/W, and that light 100% directed downward, where you want it, so overall fixture efficiency is significantly better than with MH. Also, Lumen maintenance and lifetime is better, too, so although LED fixtures are more expensive upfront, they pay for themselves in the long run. Search for “High Bay” LED fixtures.

Here’s some comparisons:

http://www.dialight.com/Assets\Brochures_And_Catalogs\Illumination\GSDunn_case_study.pdf

4

Yes, metal halide lamps require ballasts. You’ll need to replace the entire light fixture, not just the lamp.

5

Most of the manufactures of the LED retrofit kits are claiming an efficiency between 80-100lm/Watt. They also claim that a 150W LED module is a suitable replacement for a 400W HID. I was told that I can’t directly compare the Lumens between the two but instead need to look at foot candles? Apparently the LED’s create a more uniform distribution of light than conventional metal halide bulbs. As noted earlier the LED’s all point in the down direction so the light doesn’t have to be redirected with mirrors. Maybe someone else can explain this better. Hopefully this isn’t a bunch of nonsense sales pitch that I’m getting.

6

Or if the light fitting is one that is seen commonly in both types of technology (for example, E27 screw in fittings), then you can rewire the Metal Halide so that it bypasses the ballast, capacitor and igniter, and just goes straight to the lamp holder. Then you can screw in your LED lamp. Though I’d personally recommend replacing everything.

I have seen that Metal Halide does have quite a high lumens per watt, but that isn’t the whole story. LED’s tend to have a much higher bulb lifespan (you can easily get 30,000 hour LEDs, whereas Metal Halide is realistically only 10,000 hours*) and are also much lower wattage, so use less energy. Where I am, at university, they have these 150W Metal Halide spotlights, and you could easily replace them with 30W LEDs and get the same light output. Furthermore, Metal Halides tend to drop in output much more rapidly than LED’s - expect the Metal Halide to only be at 50-65% output at it’s rated lifespan.

*It’s not just the operating costs of the lamp itself that makes LED’s a much more suitable type of light for replacing Metal Halide. The maintenance costs are also a big factor, and Metal Halides have a high maintenance cost. I’ll explain more: when light manufacturers put an estimated lifespan on each bulb, it usually means that this is the average lifespan of the bulbs that were tested (a selection of lamps are tested, in order to get the lifespan). By this time, 50% of the light bulbs had failed. This is true for most light bulbs - but Metal Halide is a bit different. For MH, you have to treat the rated lifespan as the “DO NOT EXCEED” time for all light bulbs. - meaning that once you have reached the lifespan (usually 10,000 hours?) you really need to relamp the fittings. If you don’t relamp at that time, you’ll likely damage the ballast, and increase maintenance costs.

A real world example being my university; we have 32 of these Metal Halide Spotlights in the foyer of one of the buildings (in various locations). Only 5 of the fittings work. Why is this? Because no one at university knows what the tell tale signs of a failing Metal Halide light are, and even if they did, they haven’t done anything about it until failure of the lamp. This has in turn damaged the ballasts, to the point whereby the ballasts have given in and no longer work. These fittings are also a good number of years old (at least 20 years), so you cannot get the parts for them (including ballasts). Hence, the lights no longer work, and you can’t repair them, so they will have to be replaced with LED.

I’d only recommend Metal Halide if you can access the lamps on a regular basis, for crucial maintenance work. Failing that, find a different type of light fitting (preferably LED).

8

“Loyal prices” post reported.