zzzzzzzzzz wrote:
On Sun, 9 Jan 2011 19:48:28 -0800 (PST), DD_BobK wrote:

On Jan 9, 7:18 pm, " wrote:
We recently had one burnt electrical outlet at our office. The
appliance plug is also burnt as well. All the outlets at our office is
rated at 20Amps and have fuse protection. The fuse did not trip.
Anyone has a clue why the outlet and the plug are burnt? I am planning
to just replace the burnt outlets and the appliance plug, but I really
prefer to know what caused the burning in the first place.

Here are 2 photos showing the plug and the outlet:

http://www.flickr.com/photos/5423000...07/5341718398/

Thanks

Bad (high resistance) connection between the plug & receptacle neutral
contacts.

I'm betting that it took a fair amount of time (many months) for the
problem to manifest.

Get a better grade of receptacle & plug.
Make sure that the plug withdrawal force is good.

The fuse (circuit breaker?) never did its job because the amperage
draw was lower than its rating.

This is are arc-fault breakers are supposed to help. I'm with you, though. A
better outlet/plug, properly installed, would have avoided this problem
completely.

If it is a high resistance connection (which it may well be) there is
no arc. One may develop later.

If there is an arc, it is a "series" arc. The original AFCIs won't
detect it; they need an arc of around 50A (line to neutral or ground).
The AFCIs installed 2008 and later can detect a series arc. AFCIs have
only been around since 2002 and only for residential (this is office).
But wait a few years. Required use is creeping like a slow plague in
every NEC revision.

--
bud--