hot lamps

[sitelights]

In a move toward lower operating temperatures and increased safety we switched to xenon bi-pin or wedge base lamps about three years ago. Also, 99.9% of our MR covered lamps are 20w or below; there is occasional need for 35, 42, 50 and 75w MR lamps but they are used sparingly (0.1%) and only in luminaires that are appropriately sized.

Xenon bi-pin lamps operate at a lower temperature than their halogen counterparts; the consequence is a slightly diminished output and a bit less "whiteness" since they operate at a lower "degrees Kelvin" rating. "Xenon" is the term for the inert gas mix within the lamp envelope. Our reasons for converting to xenon lamps were practical (one might say "pragmatic"). Xenon lamps can be handled more easily; there is no concern about touching the envelope of the lamp except when hot. If you read the installation instructions for a halogen lamp (I do) there are cautions about depositing oils on the envelope (lamp bulb) by touching it and warnings of decreased lamp life and the danger of burns. A drop of water on a hot halogen will cause the envelope to shatter; I have a crescent-shaped scar on my leg to prove it. Xenons are available as wedge base lamps in the range of 3 to 18w and have superior performance in both lamp life and resistance to corrosion at the socket/lamp interface. The looped soft wire "pin" of a wedge base lamp provides more contact area.

The bare, uncovered MR lamp has all the hazards of the halogen bi-pins. The lamp within the reflector can be touched, the lamp envelope is very hot and will burn skin instantly and it will shatter in contact with water when the lamp is on. We have paid a premium for covered, front-glass lamps since their introduction; the bonded glass cover (like a sealed-beam lamp) prevents finger contact, shattering and burns. As a bonus the covered lamps suffer much less from mirror degradation since the aluminized, highly reflective surface of the mirror is protected from the possibility of moisture and dirt contamination that lowers performance.

The following paragraph is the equivalent of the "professional driver, closed course" subscript on TV commercials for performance vehicles.

Despite the inherent dangers of relamping "hot" all the pros do it. Imagine this scenario for a service tech balancing time against the danger of lamping "hot": (1) the system must be turned on (2) burnt out lamps must be identified (3) the system must be turned off (4) lamps are replaced (5) the system must be turned on (6) anything that doesn't light up has to be checked for (a) a bad lamp (b) a faulty socket (c) a break in the lead wire (d) a corroded connector or loose wire nut. The tech would have to turn the system on and off (a trip to the transformer/controller) each time and it is no exageration to state that this on/off state could have to be invoked a dozen times. The high watt folks will have to spend even more time since a 50w lamp requires a cool down period and/or awkward heat-resistant gloves.

A service call done by the "book" could take 10 times longer than the "in harm's way" repair and replace scenario. At this point my "inner attorney" compells me to state that a system should NEVER be serviced with the power on.

Safe equipment=safe service. Protect yourself.

[On the "manufacturers' page there is a link to THHC Lighting, a pioneer in the development of xenon lamps.]

[par 36]

Sitelight, do you find that a covered MR16 lamp with front glass gives off more heat to the socket then a non-covered lamp?

I have tried the Di Star Xenon lamps and found that they didn’t last as long as the Halogen Bi-Pin. It’s probably because of the brand. Also, is their any difference between a Xenon and a Xelogen lamps?

I know there are two or more companies that have front glass MR16 lamps. Which do you have a preference for?

Thanking you in advance for your comments,

Par 36

[sitelights]

I address this topic on the Engineering forum under "Extra heat from halogen lamps"; the largest heat differential would occur between aluminized and dichroic not uncovered and covered. A 20w MR aluminized reflector type has less heat to the socket but heat rises sharply as the wattage rises: a 20w lamp change is easy bare-handed but a 50w is not. I invoke the same disclaimer as in my original post at this point.

The manufacturers' lamp life tests are a better source of this information since it is done under controlled, repeatable conditions. Their test results are quantifiable while direct experience with a small sample is anecdotal. I too have had some abreviated lamp life problems with bi-pin xenons and this is why we switched to a wedge base xenon lamp that advertises longer life. Pin corrosion is the real problem with bi-pins of either type as well as the MR lamps.

Xelogen is THHC's terminology; I think they have created this portmanteau term (XEnon + haLOGEN) to describe their brand only.

I use Ushio MRs exclusively; Osram-Sylvania, G.E. and Philips among others manufacture covered or "front glass" lamps. We buy our MR lamps in cartons of 50 at a negotiated, fixed price; cheap lamps are just that: cheap lamps.

[par 36]

Sitelight, when you changed over to using wedge base xenon lamps, what did you do to the existing fixtures that you had in the field that were bi-pin type of fixtures?

Also from other posts, I haven’t seen you mention Par 36 halogen lamps. Do you ever use them and what is your opinion of them?

Par 36

[sitelights]

We carry a good supply of wedge base sockets at all times. Systems under warranty or a service agreement get the upgrade without charge. Path light conversions take the most time followed by floods. The change out takes from 5 to 15 minutes depending on type. If the failed luminaire has a bi-pin halogen we replace it with a bi-pin xenon; if the luminaire has a failed xenon we replace the socket and lamp with wedge base xenon. The upgrade to wedge base xenon was implemented by our path light supplier about three years ago so we are mostly upgrading older fixtures. The flood conversion is done under the same circumstances: if the original halogen shows signs of pin corrosion or is reluctant to light up with a new xenon bi-pin we switch. Of course, this requires good records; any changes are marked on the job jacket. If there is some extra time available we may change out every bi-pin socket/lamp on a system but this is mostly done on luminaires that have been in place for 5 or 6 years. Understand that we work mostly in the Philadelphia suburbs so we tend to wait out the rush hour (3:30 to 6:30 PM) on a job site or do fill-in work on nearby existing warranty or service agreement systems as "drop in" work i.e. pro-active service calls.

Our conversion wedge base sockets are purpose-built; by that I mean that they have been made to specifications superior to the run-of-the-mill types. If this improved socket was not available to us we would continue to replace failed bi-pin sockets with new bi-pin sockets plus xenon lamps. Our path light and deck light supplier (Escort) supplies us with their proprietary wedge base socket pre-assembled with a 36" 18/2 lead unless we specify another length for deck applications.

I am not anti-PAR36 (your handle indicates that you are pro-PAR36) but my very infrequent use, mainly in underwater fixtures, has a firm basis. Until a few years ago the PAR36 lamp housing (the lens/reflector sealed beam unit that protects the small halogen capsule) was sealed with silicone between the terminals on the back of the lamp; now they are heat sealed with molten glass like an ampule. My reservations about the silicone shortcut kept me away from the PAR36 lamp. I've seen many full of water. In addition, they are relatively expensive, come (as halogens) in a very limited range of beam and watt and call for a large luminaire to house them. On the plus side they have no socket hence there are no socket problems. We carry one 36PAR36FL halogen on each service vehicle but we try to keep 50 MRs, 50 bi-pins and 50 wedge base lamps/sockets as normal stock. I have always considered the PAR36 an in-ground lamp and then only if there was a surface cover lens. The pit-style (PVC tube) PAR36 lamp holders tend to fill with debris rather quickly and have a very "low rent" appearance.

[sitelights]

A lengthy post "underlamping : overlamping" in the Safety forum touches on the PAR36 lamp; it is possible to find every mention of PAR36 lamps by using the the search function on this site. Note that to search, the keyword must have more than 4 characters or letters. Example: "PAR36" gives 4 results but if "PAR 36" was searched there would be no results.

In general, there are many instances where a member or a guest seeks information but doesn't have the time or inclination to plod through all of the posts. Many of the questions posted have already been addressed; these posts would be instantly accessible if the search function was used. Since guests as well as members can use this shortcut they may be missing rapid access to posts on their interests.

It may be that this feature of the lowvolt.org is being missed. The web site wizard, Steve Gass, and I are going to brainstorm (an accurate description of our sessions) on making the search function a more visible and/or functional tool for getting the most out of the site.

[A recent change to the home page now puts more emphasis on the search function with bold type. This change was made on 03.15.04]