I got a call from a past customer the other day. Did a remodel and rewired about 60% of there house. Everything is fine with the "new" stuff but they are having problems in there existing dining room. I haven't been out there to see what it is and you can only depend on the homeowners for so much truthful information over the phone. It seems light bulbs are physically exploding but this is only the second time it has happened it 3 years. I do need to ask him if it is the same light socket that has the problem or separate ones. I am doubtful he is going to remember. Fixture still works and he already replaced the bulb. Just want to prepare myself before I put on the tool belt. It happens so sporadically I am not sure what I might find and would appreciate any ideas.

Thank you,

Shawn

My first guess on this would be defective light bulbs. The first bulb that exploded was probably manufactured on the same production run as the second bulb that exploded.

My second guess would be an over-voltage condition caused by an open (or intermittently open) neutral. Examining each and every neutral connection on the circiut would be the only way to eliminate this possibility.

My third guess is that you have been given all the details of the problem.

Unrelated specifically, but along the same topic:

There was a thread sometime back about somebody with exploding lightbulbs, I believe it was on their garage light. What was the outcome of that one? Anybody remember?

P. S. Could water be landing on the bulbs somehow?

[This message has been edited by ThinkGood (edited 11-27-2003).]

i once had a bulb exploding in a lava lamp. Reason: It just was damn cheap, bad quality.
it exploded right when i switched it on and even blew the 16A fuse in the panel.
good the lava bottle was over it, so no glass parts could fly out.

The worst for me was finding a rural heat pump that had 263 volts {running} at the contactor {with a 230V nameplate.} The long distribution circuit had been somewhat overcompensated. When asked, the homeowner said he bought incandescent lamps by the truckload, but complaints to the utility had been fruitless. That changed with a phone call.

Bjarney, I had live voltage like that at my mom's house about ten years ago. Called the POCO, get the customer service driod, who didn't know what "voltage" meant. "Are the lights on?" "Yes" "So what's the problem?"... I told her to just write it down that I was seeing 132V, which should be 125V max, and give it to someone in their technical depts. A few weeks later two linemen with a DVM drop by and measure the voltage, yes, 132V. Bad neutral? So they measure the 240V, they get 265V. Can't blame the neutral. They go visit the local substation, found a few bad capacitors and replaced them. Still 132V (they saw that we had a good DVM and knew how to use it, so they just called on their cell phone for us to measure it). Turns out that the town's loading of the 3 phase distribution net was unbalanced. It took about a month before it was corrected.

My line is at 124V at 11:59 Thanksgiving day right now.

One other thought, is the bulb a halogen by any chance?? The oil from your fingers can cause them to explode sometimes right away sometimes slowly.

It happens because the oil causes on part of the bulb to cool at a different rate than the rest of the bulb. Not a big problem in the home kind, but lighting instruments are really quite impressive when they go.

As far as published standards or “treaties” between utilities and appliance manufacturers in the US, the granddaddy reference is ANSI C84.1-1995, but you have to buy that. An adopted, condensed version {that differs on one entry} for 600-volt systems is ARI Std 110-2002 at www.ari.org/std/standards.html

It is very important to understand that, before placing blame on voltage levels, you have a meter that is known to be accurate—typically having a met-lab sticker less than a year old. Also, understand the potential for published errors of the meter used. For instance, a Fluke 87 on a higher AC-volt range for 60Hz is listed at ±0.7% + 2 counts. So, for a 120V measurement, the acceptable displayed range for that particular “in-calibration” meter could be 118.96 — 121.04V.

Do not confuse resolution with accuracy in electrical measurements with digital meters. Also, operating temperature, battery condition, signal frequency and deviation from a zero-distortion sine wave affect measurement accuracy.

Be aware of the difference between service and utilization voltage, and how the two relate to utilization-equipment nameplate voltage.




[This message has been edited by Bjarney (edited 11-30-2003).]

Well I went out there last night and spent about 5 Minutes on the problem. Most of them to put on the tool belt and set up the ladder. Looked at the switch first.....dimmer with an air gap in the wrong position. FLicked it over and wallla....instant action. One bulb burned out (aka the supposedly blown up bulb). Why do I always forget about the stupid airgap switch? Thanks for the responses and the help. Glad but at the same time not that it was something so simple.

Interesting! An air gap switch?

20-questions time: ( )

How does that work, what does it do and do you just adjust it or do you have to replace the entire dimmer switch?

I assume this is only present on high-end luxury dimmers?

25 years in the business and I have not once ever heard of an 'airgap' in the dimmer switch. Please can someone explain something I have never heard or known about.
Thanks
Pierre

Pierre, I answered my own question shortly after I posted.

I did a search on google.com and it turns out that in some very fancy electronic dimmers (the ones where you have to press a rocker switch to control the lights), there is a tiny pull-tab switch underneath the faceplate.

By opening the switch you totally cut off current to the lightbulb. They call it an air-gap switch because that's what interrupts the flow of electricity -- a gap of air between the two contacts.

This was a PDF of installation instructions for some dimmer -- don't remember the brand, but I guess it will turn up if you do a search on "dimmer" and "air gap switch".

It is a Lutron Maestro. It has an airgap because it sends a small amount of voltage when the switch is off to complete the circuit and operate some LEDS. Voltage might also be needed to dim from multiple locations. Not sure the exact amount of voltage but it must be enough for it to be required. http://www.lutron.com/maestro/