Just a saftey reminder.

[itsmoked]

A house burnt down on my street the day before yesterday. Pretty rare event nowadays. Maybe 2 houses a year burn in my city of 60k.

Fire started inside the garage and spread via the attic to the house. The cars gas tank ruptured causing a real ramp-up of the disaster.

Faulty wiring was the cause. I watched as the fire inspector dragged the faulty piece of wiring out of the garage thru the 8 fire trucks from our town an two others. He photographed the chunk of faulty wiring that was laying on the ground several times. Then drug it back to the house-remains and hung it on the fence.

Last nite I walked past the remnants and noticed the "wire". I went over and looked at it.

Orange 14AWG extension cord.


Another point in the extension cord column!

We should probably all review our extension cords and toss any with even the smallest defects.

 

[itsmoked]

I always spell safety, saftey...

Where's my extension cord I'm gonna hang myself...

 

[Skogsgurra]

Right. But you know, as long as all letters are there - no-one notices. I had to search long for that "saftey"!

I am not so sure that there was a defect in the cord per se. It may very well also have been abused (more current than designed for). That happens often during cold days and nights when extra heating is needed. Especially if the cord hasn't been "uncurled" (rolled up in its holder).

BTW, could one say about the house that ItSmoked?



Gunnar Englund

http://www.gke.org

 

[itsmoked]

<grin> oh yeah, it smoked alright..

 

[zeitghost]

Reminds me of the days when I used to fix TVs in the field.

One place I went to had a 13A socket wired up with phase & neutral reversed (so that neutral was switched, a classic gotcha for the tv engineer in the days of non isolated chassis... 240V makes you twitch a bit).

And the wiring used was two core bell wire.

"It was installed by a proper electrician, mista"...

Yeah.

Right.

 

[ScottyUK]

zeitghost,

Fixing appliances was a sideline of mine at college. One of my early acquisitions while messing about with TVs was a 240/240V isolation transformer. Big bonding clip onto the metal chassis to earth it.

I came unstuck while working on an old Cossor oscilloscope. The name 'Cossor' dates it a bit doesn't it? I got a bit careless and discharged some part of the HT through my body: I'm not sure if I caught the full 14kV but the kick made the punch from a car HT seem quite lightweight. I was very cautious after that - I still am: a lesson learned and never forgotten.


----------------------------------

One day my ship will come in.
But with my luck, I'll be at the airport!

 

[RobWard]

One evening I was working after hours on a prototype machine.
There had been a problem so we went to have a look. It was an early prototype and we had a lot of problems with the electronics so didn't think much about it.
My colleague undid the access panel at the back and stuck his head in, then went very very still, and in a panicky voice requested that I rather urgently disconnected the power.
Having done this I went to see him with the bare conductors from the power inlet (32A 3phase supply) millimeters from his face.

It seems that someone had caught the power lead with the forklift truck in the afternoon while the machine was off and pulled it so hard it had broken the two restraining clamps (yeah - two. Belt and braces job, we thought) and pulled the conductors from the connectors.

The culprit, instead of reporting the problem, then stuffed the cable back through the entry into the machine.

The next morning I had a bit of a shout at a director, who to be fair, wasn't at all impressed with people who'd do such a thing. He called the workforce together and explained how someone could have been killed. He went on to say that if he ever saw such a thing happen, he personally would remove that person from the site instantly.

So, at least we felt that the directors did care, even if the workforce don't.

(As an aside, we assume that the culprit must have known the danger, but when we saw one colleague fixing the loud speaker from his work area radio we had to wonder. The cable had been pulled out of the speaker cabinet, so to repair it, he took some chewing gum and used that to fix the bare wires to....the wooden cabinet.
You see, the wire still went from the radio to the speaker so it should work, right? Hmmmm)

&quot;I love deadlines. I love the whooshing noise they make as they go past.&quot; Douglas Adams

 

[OutToLunch]

Aoccdrnig to a rscheearch at Cmabrigde Uinervtisy, it deosn't mttaer in waht oredr the ltteers in a wrod are, the olny iprmoetnt tihng is taht the frist and lsat ltteer be at the rghit pclae. The rset can be a toatl mses and you can sitll raed it wouthit porbelm. Tihs is bcuseae the huamn mnid deos not raed ervey lteter by istlef, but the wrod as a wlohe.
--------------------
Sure, proper spelling is important, but it doesn't seem to be absolutely necessary - especially in an informal online forum.

 

[ScottyUK]

Bad spelling and bad grammar set off all sorts of alarm bells, especially in technical documents:

Report rushed?
Report written by someone who doesn't care?
Report written by a cretin?

What else is wrong? The calculations? The conclusions?

That said, it is impressive how the human brain can interpret the nonsense in your post and read the sentence.



----------------------------------

One day my ship will come in.
But with my luck, I'll be at the airport!

 

[zeitghost]

Scotty, I've got a Cossor 'scope from the late 60s, early 70s. All transistor but it gets very hot...

 

[ScottyUK]

Mine was an ex-Royal Navy instrument. Dual timebase, active probes, all sorts of toys. Beautifully built: l discrete components on small PCBs interconnected by wiring looms. It was a maintenance nightmare. It was similar to the Model 4000

http://www.marktplaza.nl/Cossor-oscilloscope-model-4000-1350349.php

but had a few changes for the military - screened power cable, Cannon military style connector for power inlet, a front cover housing probes, attenuators, terminators, etc. I wish I still had it.


----------------------------------

One day my ship will come in.
But with my luck, I'll be at the airport!

 

[felixc]

Back to the orange cable, I've had two outdoor pool filter pumps. Don't ask, they were not overloaded and the 120 volts is at 120 volts. They have a nice black molded cable. The cable gets warm when the pump is on. And more if the cable is coiled. They're running at 7-8 amps. The molded plug melted down during the second year. Then every next year, each of the 3 cable connections within the motor casing fused. The on-off switch also fused. These pumps and the cable were UL and CSA approved. I've cut them to their shortest length up to the power receptacle.

I repaired and improved at each time, but I can imagine legal connections catching fire. Regardless of the UL logo, which is only useful to the manufacturer, who will tell the judge and the insurance company that they have a file and they passed the tests. My orange cable? Both ends oxidized rather quickly, and the plug end almost melted once. I replaced with those yellow Leviton connectors.

I don't like to think about those who don't know, or who don't care about their electrical equipment. The sort of thinking that makes me afraid of selling my cottage and rent an apartment, to get smoked by the neighbor.

 

[itsmoked]

That sounds like maybe the chlorine is attacking the brass connectors or ?

Your cords look like this?

If they do then they might cause this:

 

[zeitghost]

Is the end of that cable forming a loop?

 

[itsmoked]

zeitghost; No er.. yes.. hmm how to state this. The cord end is just to the left of the picture. The cord essentially makes a 180 and then runs back along itself about 16 inches with the female end laying against itself.

So yes a loop but not a real 360 kind of loop.

 

[rmw]

Hey, I just asked a question in another thread regarding appearant power. Probably the only thing I remember from the EE courses I was forced to take as an ME is that reactive power heats the conductors, and that in the winter some utilities will adjust their power factor to heat the transmission lines to melt the ice off of them.

Whether that is true or not, I remember it being said.

That said, if it is true that reactive power heats the conductors, wouldn't this type situation (the thread topic) be exacerbated if the orange extension cord were used for inductive loads instead of purely resistive loads?

It would seem that felixc's use of the extension cord to run pool pump motors would be a worse case scenario vs putting the same amount of power through the extension cord to run lighting, space heaters, or other types of purely resistive loads.

Huh?

rmw

 

[Skogsgurra]

While the ice-melting myth might be true - or not - it is not something that comes into play here. Not even close. It simply looks like the cord has damages to it. Missing strands have reduced the total area and caused the overheating.

Gunnar Englund

http://www.gke.org

 

[rmw]

I was addressing the use of extension cords for higher amperage inductive vs purely resistive loads in general, not addressing any issues relating to the cord shown above.

Was I mis taught about the ice melting (myth)? What else did they tell me about electricity that was wrong?

Maybe they should have just used the beer foam analogy instead. I am sure I would have remembered that one too.

rmw

 

[resqcapt19]

In many cases the cord is coiled and hung from a metal object such as nail while supplying power to a load. This can and has resulted in enough heat energy to cause fires. This will occur even if the cord is not overloaded.
Don

 

[Skogsgurra]

Sorry to such a bore folks. Coiling the cord and hanging it on a nail doesn't produce heat either.

Yes, there is inductive heating - and it works. But an extension cord just doesn't do that. The reason is that there are two active wires in the cord (plus a Protective Ground wire in most cases). The magnetic field from the two wires cancel and there is no net field and no heating.

The temperature rise that can be observed in a coiled extension cord comes from reduced cooling and not from any magnetic effects.

Gunnar Englund

http://www.gke.org