HPS vs MH

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lile001

lile001

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Midwest
THis isn't actually a code question, but it comes up in electrical lighting design. High Pressure Sodium versus Metal Halide lights - what are people using more these days?

I am putting some lighting in a parking garage, using some fixtures designed for the purpose. I have read that HPS has longer lamp life, higher lumen maintenance over it's life, and higher efficiency. However, Metal Halide has a far better color than the yellowish HPS light, making the space look 3X brighter to the eye for the same amount of lumens. (this is more a function of the response of the eye and perception in the brain than physics). Thus one could use less light and still achieve a good lighting level. I also read that sales of MH are growing fast, while HPS is leveling off, due to the publics rejection of the yellow light versus the whiter MH. Any opinions?

[ April 20, 2005, 10:33 AM: Message edited by: lile001 ]
 
Re: HPS vs MH

Here's pretty much an un-scientific answer. HPS sucks! Seriously, IMHO perception means more than what a light meter tells you. Outdoors most people will tolerate HPS mainly because they're used to it. Indoors the perception is that it is un-natural and tends to depress people. There has been alot of research done on lighting and what I've seen is that people are happiest with something more closely resembling natural daylight. A few years ago I converted all the HPS site lighting at the manufacturing facility where I work. Afterward I received many thanks for "making the site SO MUCH brighter". I didn't upsize anything - just converted to MH. Granted, they were all brand new lamps at the top of their lumen curve at the time of conversion but some 2 or 3 years later the perception of improvement over the way it used to be is still there. :cool:
 
Re: HPS vs MH

I once heard a story about an attendant in a parking lot that had HPS lighting. Apparently people frequently came up to him after dark thinking that their car had been stolen. He always told them to just come back tomorrow morning. And they always found their car the next day. Apparently, people would see their car and not realize it because the color looked different.

Vertical illumination has a lot to do with how bright an area looks. The louvered fluorecent lights in open offices are a good example. They always make the space look dark because they don't put much light on vertical surfaces.

Likewise, a lot of the new cutoff fixtures made to reduce light pollution don't throw much light on a vertical plane. (Have you ever seen anyone take a light meter reading with the sensor pointing sideways? Probably not, but sometimes that is just as important as the amount of light falling on a desktop or floor.)

Steve
 
Re: HPS vs MH

I attended an IES seminar a few months ago where the speaker talked about how even though HPS has a higher efficacy (lumens/watt) than MH, the amount of light visible to the human eye at night is actually less than MH. The reasons are technical (have to do with the way the eye perceives and processes light) and boring, but it's yet another reason to use MH over HPS.

Also, good luck trying to tell the difference between white, silver, and gold cars under HPS light. Notice that the car dealerships always use MH (and a lot of it).

The best outdoor lighting designs utilize uniformity over quantity. A parking area with an average illumination of 2 foot-candles and a maximum/minimum ratio of light to 4:1 will be more effective than one with an average of 5 foot-candles and a max/min of 10:1. In other words your eyes will adapt to less light if it's uniformly distributed, as opposed to a bunch of bright spots with dark spots in between.
 
Re: HPS vs MH

I have been using MH for a couple years now. It's because of the visibility factor. The eye can see better with white light than yellow.

When I first started we had fluorescent in factories, then upgraded to mercs, then HPS, then MH, and now we are gooing back to fluorescents--T8 & T5.

If you remeber incandescents in factories, you got to be retired! :D
 
Re: HPS vs MH

In our mfg. bldgs., we jumped on the HPS bandwagon also in the early 80's.

But HPS is "crummy" light, thus we are slowly retrofitting it with Metal Halide (Pulse-Start where possible).

But, we do use HPS for exterior lighting & will continue to do so.
 
Re: HPS vs MH

MH light is the closes you will get to natural light.

When MH lamps go out, they go out. When HPS lamps are nearing end of their life, they will come on,off,on,off.

We never recommend HPS for a parking garage for the reasons stated above. However we continue to use them for outside lighting because they are easier on neiboring windows.
 
Here is the result

Here is the result

Because of using MH lites, and paying attention to vertical footcandles (new lights are designed to throw light sideways instead of straight down) we were able to use 33% less fixtures, 33% less energy, cut 30% of the money out of the budget, and add some photocells to use daylight at the edge of the parking garage for more energy savings. Everyone compelmented us on how much brighter it is in the lower levels. It isn't brighter, but the light is being cast horizontally, lighting objects, instead of vertically, lighting the floor. It looks brighter with less light.
 
Lawrence,

That is some good info, thank you, and in less than two years at that!

Just kidding, really 30% is a big number and it looks brighter, SOLD!!!
 
I am spending a lot of my time lately looking at lighting and efficiencies. I also have a parking structure with HPS and I am looking at something different based on the colour of the light. The colour of the light is somewhat of a safety issue. If someone tries to identify an attacker under HPS light they can't identify the colour of clothing very well. While Metal Halide will look better there are other things I am considering. Metal Halide will require substantilly more maitenance because of lamp life. Depending on temperature, I would be looking at T5 technology. Lamp life is a lot longer and energy used is a lot less. Also with T5 you have the ability to switch lighting rapidly with occupancy sensors. This will allow for even greater savings in energy. Also from a maintenance perspective if you loose one T5 lamp it is not a major issue. With Metal Halide if one lamp goes out it leaves a big dark spot. This issue has big impact on arenas that I also maintain. Metal Halide seems to be loosing ground in the industry. There are already conversions that have been made to T5. I am going this route also based on the ability to switch lights on and off rapidly. Now if we have an hour of unused ice the lights stay on based on warm up/cool down time. With T5 I can turn them off for this time. More savings!
 
OK Electrical Contractor.

OK Electrical Contractor.

I do a lot of warehouse re-lighting here for a large property managment company.
They really pushed the use of MH, which for sure changes the light level in the buildings.
I pushed the new T-5 H.O high bay replacments which come in many config's Tandem X 3 with chrome deflectors put out a brillant light, at a much cheaper operating cost, although they have a slightly hight front end cost, (lamps are expensive for fluorescent) The locations where I have installed have had great reviews! people love the light color, level and the instant on of fluorescent. They are slow to come on but I think they are the way to go.
On the other side I have one customer who we installed MH for that requested a change back to HPS, they store records, boxes with labels selected from fork trucks. They claim that the yellow light gives them less glare, and easier reading of labels?
If you use MH I would suggest the quarts light start, so at start up, or in places that get power bumps, you have some light until lamps fire up.
Tony
 
Mh/hps/t-5

Mh/hps/t-5

The T-5 High-output "bay" fixtures have been getting great reviews around here. I've seen a few retro-fit projects replacing HPS and M-H and a few new facilities. At mounting heights up to 20 ft every person I've talked with has been well pleased with these new fixtures. As mentiond, lamp replacement cost, the fact that the loss of a few lamps doesn't make an area dark, and of course, energy savings are often bragging points.
I have been told there is also a tax advantage available for replighting with the new energy saving fixtures.
Definitely worth lookin into, IMHO.








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