Lamp Life

[JC Lighting]

I am experiencing MR-16 and T3 lamp life significantly below the marketed rated hours. I do all my own installation and have verified voltages are between 10.5 and 11.5 on all my jobs. However, I have a number of installations with 10% or more of the lamps lasting only a few weeks. I use whatever lamps come with the fixtures. Most of the time these are common brand names.

Comments please.

Jim C.

[sitelights]

Some downmarket manufacturers supply lamps of inferior quality as marketing advantage; no fixture makers also make lamps so the bottom feeders supply the absolutely cheapest lamp (even a penny makes a difference) to hold a price point. That said it would seem to be a knee-jerk function of marketing mavens to use as standard whatever is the low ball price item of the moment.

The top brand lamps are also subject to premature failure so a "name" is not always a guarantee of longevity.

We as professional landscape lighting designer/installers have only the lamp manufacturer's specifications to work with. Lamp life is a mystery and a very hot topic on this site; a thorough review of the appropriate forum would demonstrate the frustrations inherent in any attempt to discover an adequate formula for calculating this subject.

Utilizing lamps (MR, J type, wedge base, xenon, etc.) included with a fixture is problematical for a number of reason: with the MR you are commited to the beam spread ordered and supplied and cannot second-guess yourself; the lamp may be a different make and batch number for each fixture purchase so there is no consistency; a defective batch cannot be identified since there is no continuity in numbers of similar types and lamps outside of the manufacturer's specification cannot be tracked.

Our minimum purchase of lamps is by the pack: with MRs this is 50 (we use Ushio only; this is not an endorsement but they are made in Germany); J-lamps 50, wedge base 100; these are standard packs not the "master pack" which might contain 4, 6, 8 or more individual packs. The semi-bulk purchase allow us to identify a bad batch by percentage of failures and make a claim for replacements. Individual lamp failures are not worth the effort to register a claim.

In this regard we experienced 3 packs of 50 Ushio MRs with defective base cement; the pins would push up into the reflector housing on installation. Our report of this problem resulted in a recall of the entire batch which might have been thousands of lamps.

We do not bother with individual RGAs but we do accumulate "failed on install" lamps and we will file a group claim if more than 2% failures are encountered over a fairly short (30 day) time frame.

The reality of lamp failures over time is a function of keeping good records; it takes only a moment to note "install" failures on the job jacket. It is the ability to track unusually brief lamp life in a quantitive manner and seek credits from the (single) supplier that alllows a remedy. The sales counter staff will certainly will roll their eyes over a single (or 2 or 3 or 4) "failed on install" claims but a carton of 20 or 30 tends to receive proper attention.

[JC Lighting]

I went by a job yesterday that I installed about 6 weeks ago. I found a bad MR-16 BAB. (It was a "tapper" like I spoke about an another recent post.) I know there are significant differences in lamp manufacturer's offerings but it hasn't become a priority for me yet so I never paid much attention to the brand name before. I opened up the fixture expecting to find an inferior lamp manufacturer's name. It turned out to be an Ushio. Your method of buying in traceable batch or lots seems to be the way to go.

Thanks

[tomwilllight]

I use only GE Constant Color lamps. Avoid the CG versions because GE derates their life. If you have a well-sealed fixture, you don't need the cover glass. I get very reliable life from them. I cannot say the same for any other manufacturer.

Voltage must be checked very carefully and only under load. At first, I used "chopsticks,” 2 sharpened irrigation flag wires with a socket attached. Put the lamp in the socket and the sharpened ends in the fixture and touch the bare wire with the meter probes. It worked, but now, I use the MR16 tester made by Cast and it works well.

I was advised long ago to use only a true RMS meter and I found they are very accurate and not cheap.

Some new information I picked up at the AOLP conference from one of our smartest distributors.

Voltage drop tables were all prepared in a lab with an ambient temp of 72 degrees. With each decrease or increase of 9 degrees, the voltage changes 2 percent up or down. The colder the wire the more resistance drops and your voltage goes up. If you set your voltages in the summer with your wire on top of the ground in the direct sun at noon, you may have serious problems with over voltaged lamps in the winter. Michael Hooker warned me about this years ago and I didn't understand what he was saying.

Could this be the core problem behind many of our mysterious early losses?

We need to rethink all our voltage drop tables and think hard about when and how we check voltages.

I look forward to your feedback.