Burnt Terminals on Par 56 , 12v lamps

[LeeB]

We have had approximately 10% failure on a lighting retrofit we installed several years ago. The fixtures are a 240w, 12v Par 56 can and what we have found is the wires and fork terminals are burnt. All of the connections were tight and and the fixtures were on different circuits. We sent them back to the mfg., LSI who were more concerned about defending a claim then finding out what was happening. (We told them we were not filing a claim, we just wanted to understand what was happening) We also contacted GE regarding the lamps and they say they have no reports of this problem with their lamps.

Has anyone experienced the same thing? Any ideas?

I appreciate the input I get from ya'll.

LeeB

 

[dbuckley]

Scratch the comment about ceramic holders, if you've read it; the PAR56 240W 12V is only available with screw terminals, not the GX16d.

So, screw terminals: these are bare metal terminals (no plastic bit), with silicon wiring, crimped?

 

[broadgage]

Was the wire thick enough ? 240 watts at 12 volts is 20 amps, suggesting at least #12 wire, and perhaps larger.

How well made were the crimped connections ? cheap crimps, a cheap crimping tool, or an indifferent operative could all result in a poor connection that might withstand low current use, but fail at 20 amps continous, in a hot enviroment.

Cheap fork connectors might also be marginal at 20 amps.

For relatively heavy currents I normally solder rather than crimp the connections, if posible.

 

[Dennis Alwon]

I can only imagine the tremendous amount of heat produced by these. I will assume they are halogen bulbs and we all know the heat that just a 50 or 100 watt bulb puts out. LV fixtures have always been notorious for burnt sockets. I think the problem is the design of the fixture-- trapping the heat rather than having air holes to let it breathe adequately.

I have never used these bulbs-- is this the animal? Seems like a large wire would be needed for this unless the trany was pretty close.

 

[dbuckley]

I have never used these bulbs-- is this the animal?

Thats there or there abouts.

These lamps are most widely used in the entertainments lighting area, and are listed in the GE showbiz lamps catalog, along with many other somewhat non-mainstream lamps.

The PAR lamps of significant wattage do get as hot as hell, which is why most of the time the bi-pin GX16d base is used, which plugs into a ceramic connector, but some PAR lamps, particularly the lower wattage units (though with some exceptions) use the screw terminals / blades. And you need to be a bit leery how you connect to the screw terminals / blades so they dont melt...

Trivia - the number after PAR (eg 36, 56, 64 etc) is the diameter of the lamp in eith inches...

 

[LeeB]

Hi Dennis,
Thanks for your reply!
That's the animal. They are theatrical lights commonly referred to as " Par 56 Cans". The tranny is located in the fixture and the factory crimps on the leads appear to be well made. The wire appears to be #12 with high temp insulation.

 

[dbuckley]

Do you need the unusual beam profile of this particular lamp?

Standard PAR56 mains lamped parcans with ceramic lampholders don't suffer from screw terminal problems, but are not available in anything like the same beam width (VNSP - "Very Narrow Spot")

The only other thing that occurs is duty cycle; some of the par lamp's cant run at continuously and get anything like the rated lamp life, I'm, thinking the 28V ACLs which most folks advise no more than 50% ontime or they drop like flies, but then again these only have a short life anyway... Perhaps the manufacturer never intended thios particulat fitting to run continuously but only used as a special effect?