Covered Lamps

[Eden Lights]

It's sinking in over time, At first I said to myself we don't need covered MR's just better fixtures. Now I realize that would be a perfect world that's not quite here yet. During the last year I have taken over the maintenance of several properties and I realize it's because the owner's are not happy with the constant lamp replacements. What was causing all these problems?? One sytem which had been installed about one year had 12 of 16 lamps bad and several of the lamps looked brand new, except for the bugs, black specs, and etc. that where inside the lamps. I replaced the lamps with covered lamps and I havn't had a failure in the past six months. The success from that maintenance landed me a 50 light installation which was completed with Hadco 616's, which I consider a sealed lamp fixture. The install is one year old this week and all the MR's are still burning with regular GE percise lamps.

[sitelights]

I must be getting lazy: it took me over a year to respond to this post!

It seems to me that the high failure rate (12 of 16) is attributable to the "cascade" effect. As lamps fail one-by-one the voltage slowly rises so that each lamp failure contributes to additional lamp failures. As the load on the transformer diminishes voltage can exceed the target voltage of, say 10.8 to 12.0v and thus shorten lamp life. This is why regular maintenance is a key factor in low voltage lighting systems using "distributed" (one transformer) supply as opposed to "individual" (dedicated transformer for each lamp) supply mostly associated with interior lighting.

Covered (front glass) MR-16s (11s and 8s too) have a different effect on performance in that the mirrored reflector (MR) deteriorates in damp locations if it is not protected from moisture. The mirror finish is applied to the inside surface of the MR lamps in both the dichroic and aluminized types (search either word for further discussion) and the front glass converts an open MR into a "sealed beam" lamp. Mirror deterioration adversely affects lamp performance but it is doubtful that it affects longevity which is a mystery to everyone including the lamp manufacturers. Lamp failure rates are covered in other posts to this forum.

As an aside, there is a wonderfully hilarious sub-theme in Thomas Pynchon's novel "V" about a light bulb that won't burn out. The makers (I think Pynchon actually uses the word "Osram") dispatch a "hit squad" to terminate this very dangerous lamp. This riff is set in wartime (WWII) Germany. Pynchon is somewhat of an acquired taste but "PYNCHON" is the vanity tag on my work vehicle (a 1996 Volvo 850 Turbo wagon).

[Eden Lights]

I feel that in the application that I mentioned what extended lamp life was the covered lamps. This install has Vista accents with very large weep holes in the side of the fixture. The fixtures always have bugs and moisture in them, so I think the covered lamps were the answer to the problem. I recently replaced a couple of these fixtures due to mower damage and I saved them for show and tell. The fixture is full of bugs and the adjustment screws can't even be seen due to the rust damage to the head.

[capper]

Does anyone know of an on-line source for lamps...specifically MR16 FMV with a front cover? The local supply house took it upon themselves to substitute FMW without the front cover and they have to special order the correct FMV. (They tried to tell me the FMW is about the same as the FMV and I don't need the cover if there is a glass lens in the fixture.) I want what I want. I looked at Home Despot and they don't have it but I noticed the packaging for the 35w lamps is marked as 35w but the labeling on the lamp is marked 20w BAB so beware.

[Paul]

I believe that Cast has those lamps availible. You can get them through several distributors. Where are you located?

[capper]

Paul,

Thanks for the quick reply. I am located in S. Jersey and will give Cast a look.

[Paul]

You could try www.terradek.com . Gerry probably can take care of you.

[capper]

Paul,

A local distributor (Aquarius) had the Cast lamps I needed in stock. Thanks for your help & quick replies.