Plug Meltdown

[Luke Holliger]

Here is a reason why you should regularly inspect all cables and plugs. This was connected to a quad cell cyc light that was part of our house plot, and therefore is never moved. My best guess is that the connection slipped out and grounded to the housing screws. We are fortunate that this was discovered before it caused more serious damage or injury. Inspect all your plugs! (Yes this is an OLD twist lock connector)

 

[Dionysus]

Seen stuff like this countless times, usually not quite as bad as that. Quite often its simply because the electrical connections were not tight, or the strain relief wasn't relieving the strain (again leading to a poor connection). Other times because what was plugged in was drawing too much (the connectors are the "weakest link" and will overheat first), or because there was too much heat or not enough heat dissipation (you have to de-rate in hot environments or such).

Connector gets too hot at the point where the wire meets the prong or the prong itself and this causes more resistance, which further heats it.... Eventually you get a molten connector.

I completely agree, everything should be inspected periodically. At very least in a theatre lighting application I'd say yearly fixture and cable maintenance.
Indeed we just had another thread that ended up with quite a bit of talk about making sure connectors are correctly installed.

There is a reason a very large percentage of fires are electrical in nature.

 

[gafftapegreenia]

Something people don't realize is that wires that over time pressure plate terminals loosen from the expansion and contraction caused by wires getting warm under load and then cooling when the power is off. Over time the connection gets loose enough where it will arc and melt. This happens faster when a connector is moved around a lot, but as is clearly seen here, it can happen to a cable that remains stationary for years. The stranded wire of portable cord and cable only makes this problem worse. It can happen with solid wire but I've seen far fewer wall outlets with this problem that I have cables. This is part of the reason why my preferred method of wire termination will always be crimp terminals with a lock washer, which is a main reason I favor 2P&G connectors for stage use. I've been experimenting with crimp on fork terminals in 5-15 and L5-20 connectors, but I have no results yet. Connectors. They seem easy to terminate but they really take a lot of care to do properly.

 

[BillConnerFASTC]

I'd agree - a poor connection that created resistance and heated up more likely than a short which an a fuse or breaker would have protected. Just to be sure, a lot of electrical fires but cooking and heating are overwhelmingly much more often the cause. http://www.usfa.fema.gov/downloads/pdf/statistics/res_bldg_fire_causes.pdf This correlates with NFPA data.

Cooking leads the way in commercial buildings. When I studied NFPA data on fires on stages some years ago, arson actually ranked very high.

 

[Footer]

It's also J cable which should go anyway...

Sent from my Nexus 7 using Tapatalk