Hey there everybody,

I've run the lighting circuit and have been testing the light layout before I put the ceiling drywall up, but I've run into a problem that's going to put that on hold for a bit:

I've got 6 cans, each with 75 watt PAR30L bulbs. They're controlled by two three way switches, with the feed coming into one and the switch leg coming into the other. I currently have nothing else running on this circuit.

In the past, if a fixture ate bulbs more quick than normal, we assumed it was a poor connection causing a voltage drop/high resistance. However, I've never had a fixture spit them out in a matter of hours.

I was methodical when wiring these, with tight twists and a little help on the wire nuts with the dikes. I'm using Sylvania lights, so it's not cheap bulbs, since they were the most expensive bulb on the isle.

I'm wondering how I might go about testing this with a multimeter. What values should I look for on startup and when running. Also, I imagine that I need to have the bulbs in place for testing? I ask because in the last 12 hours, I have gone through $40 worth of lighting :)

thanks,
json

Let's approach this from some other angles:

1. Is the fixture rated for a 75 watt bulb? Try a 60 W bulb.

2. Is the bulb type correct?

3. Is the fixture ventilated properly?

4. What is the temperature in the fixture?

5. There is the possibililty that you struck a bad lot.

Hi there, and thanks very much for taking the time to help:

1) The fixture allows either a BR60 60 watt or PAR30L 75 watt. I've not over-bulbed it.

2) The bulb type is correct.

3) Currently, I'd say it's over-ventilated :). They're hanging in open joist bays.

4) I don't know off hand. I would have to get a thermometer to test. What is acceptable?

5) I will definitely keep that in mind, as we grabbed the last one in that box and we would have to wait for them to pull down more.

I'd be happy to pick up a thermo, but just need to know what temp might be considered too much. The junction box attached to the side of the can stated 90c!!

[EDIT]Also, the bulbs burn on startup. So far, we've not had one pop while running, just when activating the circuit.[/EDIT]

[FINAL EDIT, PROMISE]Looking at the bulbs, it's quite an odd thing. Most bulbs, when they blow have at the most a piece of filament dropped to the lens. These bulbs actually have blown glass. There are small pieces of glass laying on the lens of the blown bulbs. A lot.[/FINAL EDIT, I PROMISE]

Thanks,
Json

I think you convinced me it is extremely likely it's a bad lot of bulbs. Temperature won't be an issue on startup.

Bulbs are more likely to die at startup, because this is the time of most stress. I had some ELH lamps which have a coil like filament and they would easily pop when there was a LOT of vibration. The segments would fuse together.

Have you measured the voltage going to the circuit?

Try sticking a regular old bulb in one. If it goes, check the voltage. It is unlikely to be a problem unless it is a shared neutral circuit.

If nothing else, take the fixtures back and look for halogen or other, newer, more efficient lights.

Hi there,

The voltage at one of the fixtures that the bulb blew in is 121.8 v. Please let me know if there is anything else I should test for.

Thanks,
Json

Hi there labman, I don't know what a neutral circuit is, but I can tell you that this circuit runs a total of 6 75w cans, two 35w point lights and a single 40w at the entrance of the kitchen. Nothing else is run on this circuit.

The reason I thought it odd was because the way I ran the subsequent cans would require almost all of the joints to fail, since it wasn't a standard daisy-chain, but a split from the primary can to two directions, then a chain from there.

Thanks,
Json

Sounds like a bad batch of bulbs to me. 121 is a little higher than I'm used to (it's usually 118 here) but shouldn't cause problems. You can always try 130v bulbs, or put a dimmer on the circuit.

If it was a problem with a shared neutral, that might explain the voltage being abnormally high, which it isn't.

The shared neutral is a code compliant short cut I don't like. You take a hot off each hot leg of the box, run the circuits, and tie both to the same neutral. If all is well, the neutral carries the difference in amps between the 2 circuits. If you have a break in the neutral, both circuits have 240 volts. A bad connection can give lower voltages. Most DIY people would not have run one, but it is a possibility for high voltage. 122 volts isn't bad, that is about what mine runs most of the time.

It does sound like a bad batch of bulbs.

I love shared neutrals. They allow me to run less wire, have less wires in each box, etc etc. I did have one go bad once, the result was a melted wire nut, a few fluorescent light ballasts that were toast, and a funny smell. So maybe I'm crazy for liking them.

If this is your lamp:
http://www.sylvania.com/content/disp...m&id=003693630

http://ecom.mysylvania.com/miniapps/...20Brochure.pdf

It is already a halogen lamp.

A halogen lamp is actually a bulb inside a bulb

The description of debris , filament and glass, in the bad lamp, indicates a manufacturing defect of the halogen bulb inside. Hmmm I bet Made in China?

The voltage of 121 volts is fine, equipment is designed, to operate properly at +/-10% of nominal voltage.

Halogen lamps are very resilient to vibration and overvoltage.

Definitely a bad batch of lamps.

I don't see any warranty, but if you bring them back to the store, they should help you.

That is the style bulb I have. I've replaced all but one(I depleted the stock in my town :)), and have been running them all day with random on & off cycles and haven't had an issue yet.

I wasn't aware that those bulbs were halogen. Helps to explain the crazy price.

I went ahead an picked up a dimmer was well, since 450w is a lot of light to burn all the time :)

thanks,
json

As a side note, the Halogen lamps depend on the "Halogen cycle". You will get reduced lifetime if they are dimmed. It's kind of an evaporation from the filament and redeposit occurs. When the temperature of the filament isn't high enough, it degrades the lamp.

Thanks very much for that. There was another burnt bulb this morning, which although from the same lot, provides enough doubt that I can't put the ceiling up, so I'm going to remove all of the par30l's and take them back and replace them with br30's which are the other approved bulb for the can.

I wasn't kidding when I said I bought all of the par30L's in the town, and Lowe's said they'll have another shipment in about a month. After this fiasco, I think I'd like to have a plain filament bulb.

Thanks,
Json