Bad Electrickery

good examples of bad work

Archive for January, 2013

I Have A Crush On You

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Terminating onto the sheath of the cable can be extremely destructive- the device can function when re-powered, but the poor quality connection will eventually start arcing and overheat. It can lead to problems like: What Happens When You Terminate On The Insulation

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January 22nd, 2013 at 1:46 pm

Pull The Other One

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In a pub- perhaps someone stood on the flex and pulled the faceplate off. No sign of the screws though!

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January 20th, 2013 at 12:41 pm

How To Do Electrical And Mechanical Tricks – 1915

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We at Bad Electrickery wish to present:

how to electrical mechanical

[right-click and choose ‘save as’ – 15.9MB]

This little booklet is from 1915 and describes itself as an “an Up-to-date collection of Interesting, Instructive and Highly Amusing Electrical Tricks.” So, if you’re interested in reading some early electrical experimentation, right-click on the link and save it to your desktop.

Here’s an extract:
Beat your friend with a cat

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January 17th, 2013 at 5:31 pm

The Wonders of FP-200 & Common Installation Errors – Part 1

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I’m a huge fan of Prysmain/Pirelli’s FP-200. It gets used for a lot of electrical work, especially in fire alarm installation, because it is easy to strip and terminate, can take a bit of a bashing and offers fire resilience.

However, just because it’s flexible doesn’t mean it should end up in a knot.

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522.8.3 –  “The radius of every bend in a wiring system shall be such that conductors or cables do not suffer damage and terminals are not stressed.” ‘Other Mechanical Stresses’ in BS7671: 17th Edition.

Bend RadiusThis can be caused by poor installation, poor fixing, or some other problem that leads to the cable ending up out of shape.

The bend radius of fixed FP-200 Gold is listed as r=6D, where D is the diameter of the cable. So, if we’re using 1.5mm two core & earth for a fire alarm system, the diameter of the cable is 8.1mm. (Source)

This means that your 90 degree turn should complete in just under 5cm, and if you were doing a u-turn, you’d need 2r=97.2mm, just short of 10cm.

Visual inspection of the cable should make it obvious if  the turn is too harsh- the sheath of FP-200 goes white under stress, and once it has been bent, will not straighten out without leaving a kink.

 

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So these bends are probably too tight.

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Part 2 to follow soon!

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January 8th, 2013 at 4:04 pm

I Like It Crispy

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This looks like another case of a bad termination leading to overheating, followed by crispy despair.

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January 8th, 2013 at 12:30 pm