Bad Electrickery

good examples of bad work

Archive for the ‘Poor Quality’ Category

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

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

Live A Little

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Pulled out some live cables from an otherwise isolated light-switch. This is why it’s best to assume everything is live until you can prove it’s dead.

It is considered good practice to put any cut off cables into connector blocks. It is better to remove them entirely.

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August 26th, 2012 at 12:03 pm

In The Drink

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Placing a socket so close to the sink would generally be considered a bad idea.

The ECA website says: “BS 7671 does not specify any minimum distance for socket-outlets to be from a sink. However, regulation 512.2.1 requires external influences to be considered when selecting equipment for a particular location. Accessories used in domestic installations are not designed to be splashed and therefore not suitable for installation close to a sink or draining board. For this reason, it is recommended that socket-outlets and other accessories should be located at least 300 mm, measured horizontally, from a sink or draining board, where they are less likely to get splashed.”

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August 12th, 2012 at 6:48 pm

Gordian Knot

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Before:

After:

Sometimes you find something that is in such a tangle, the best thing to is spend a moment fixing it down and rewiring it.

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August 12th, 2012 at 2:29 pm

Cut Short

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Found in a new building. A little worrying…

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August 10th, 2012 at 4:49 pm