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Posted By: Admin Light Bulb Socket Trips Breaker - 02/21/09 01:00 AM
Quote
This happened a few months ago. A one-way bulb in a three-way socket and a short circuit inside the socket tripped the breaker switch; the bulb was a mini-fluorescent bulb.

The one thing I find odd is that I have a lamp with a three-way socket and have used one-way fluorescent and incandescent bulbs in it for years and as far as I can remember, there’s never been a problem with that.

I included a shot of the sticker saying the max wattage the lamps rated for.

- Tristan S.

[Linked Image from electrical-photos.com]

[Linked Image from electrical-photos.com]
Posted By: HotLine1 Re: Light Bulb Socket Trips Breaker - 02/22/09 01:46 AM
Bad ballast in the CFL lamp??
Posted By: packrat56 Re: Light Bulb Socket Trips Breaker - 02/22/09 04:48 AM
Not sure John, I don't think so because it was the second hot treminal and the side treminal that had the arc fault. I didn't notice any signs that would have indicated a problem but maybe there weren't any signs to notice. The copper terminal that's dead center didn't have any signs of arc fault damage so I'm thinking that the arc fault resulted when the second hot terminal became live when its switch contacts closed as the switch knob was turned. I planning on checking for other damage that may have been caused when this happened just as a precaution.
Posted By: noderaser Re: Light Bulb Socket Trips Breaker - 02/22/09 09:12 AM
What does the base of the bulb look like? Perhaps it wasn't machined right, and had a larger area on the screw or tip, causing the short?
Posted By: Rewired Re: Light Bulb Socket Trips Breaker - 02/22/09 08:06 PM
I see what looks like shiny melted copper on the right side of the terminal in question and the metal screw shell of the socket. Perhaps there was some metallic "spare part" that fell into the socket or made its way between the terminal and screw shell when the bulb was changed out?

A.D
Posted By: Ann Brush Re: Light Bulb Socket Trips Breaker - 02/23/09 08:31 PM
The answer is the three words that begin with "Made" at the bottom of the label.
Posted By: wa2ise Re: Light Bulb Socket Trips Breaker - 02/24/09 04:13 AM
Originally Posted by Rewired
Perhaps there was some metallic "spare part" that fell into the socket or made its way between the terminal and screw shell when the bulb was changed out?



Reminds me of some stupid pranks some kids in my college dorm used to do to the wall sconces in the stairwells. Those had light bulb sockets facing up, no enclosure around the bulb. Someone would steal the bulb to replace a blown bulb in their desk lamp, and someone else would drop a penny into the empty but live sconce socket. And cause sparks and trip the breaker... idiots.
Posted By: johno12345 Re: Light Bulb Socket Trips Breaker - 02/24/09 10:27 PM
Why is there a cardboard tube around it?

Perhaps that is where the risk of fire lies wink

Interesting as we dont have this sort of three way fitting in the UK.
Posted By: HotLine1 Re: Light Bulb Socket Trips Breaker - 02/25/09 01:02 AM
Johno12345:

Lamp sockets come with a 'cardboard' sleeve here in US; sleeve promarily is the 'insulator' from the hot/neutral screw terminals on the side of the socket, to the metalic outer shell (sometimes brass finished) We also have other configarations. There is also a lot of 'junk' as Ann was leading to above.

The interior of the socket is wired screwshell is neutral, center tab is 'hot', secondary tab is for 3 level lamps. 1 'on' is low wattage; 2 'on' is med. wattage; 1 & 2 "on" is 'high' wattage.
Posted By: Texas_Ranger Re: Light Bulb Socket Trips Breaker - 03/05/09 01:37 AM
3-way bulbs are obviously a particular US thing.

European Edison base sockets are built differently, they don't have live threads, instead they're built with two bottom terminals. The actual thread is isolated from the shell by a plastic ring. Never seen one of those fail, the only typical problem: overheated cord, PVC gases out creating acidic smoke, terminals corrode.
Here's a pic:
[Linked Image from electrical-photos.com]

The outer shell is also considerably sturdier than its US counterpart.
Posted By: pdh Re: Light Bulb Socket Trips Breaker - 03/05/09 09:17 AM
Originally Posted by noderaser
What does the base of the bulb look like? Perhaps it wasn't machined right, and had a larger area on the screw or tip, causing the short?
It doesn't look like the tip would be the problem. From the looks of the damage, the screw part of the bulb extended down to where the ring of the 3-way bulbs are, and the 2nd hot terminal reached it just barely. Most of the arc damage is at that 2nd hot terminal. There's a bit of screw shell damage. What Ann Brush said seems to be the cause.
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