What they are, why they are dangerous, and how to find them.
Poor wire connections are a common cause of electrical faults. They are a human made problem which happens when the wire connection is either over tightened, under tightened or completely missed i.e – screwing into the wire insulation. This post will go into more detail about why they are bad, if not dangerous, and what you can do to prevent them.
What Is A Bad Wire Connection?
A bad wire connection happens when the termination connecting two or more wires is either:
- Over tightened. Leading to wire strands breaking.
- Under tightened. Leading to the wire loosely touching or popping out.
- Has no connection between wires due to screwing into the insulation or missing the wire.
A poor cable connection is an avoidable but commonly seen problem in domestic electrical work.
Where Do Bad Wire Connections Occur?
Bad wire connections can occur in the screw terminals located in
- Switches
- Outlets
- Fittings, such as lights
- Circuit breakers
Or any other cable connection which might occur in a
- Strip connector
- Crimp
- Lug
- Soldered connection
- Or a range of other cable connection methods.
Why Do Bad Wire Connections Occur?
Bad cable connections are mostly an avoidable human-made error which occurs mainly due to:
- Carelessness of the installer
- Lack of knowledge of the installer
However, cable connections can also become loose if:
- The cable is part of something that moves a lot, the wire connection can become loose over time
- Big temperature fluctuations at the cable join can cause the termination to shrink and expand causing it to become looser over time.
- Vibrations from equipment nearby can loosen connections.
- Oxidation of the cable connection if located outside in the weather.
What Does A Bad Wire Connection Look Like?
To check the connection, gently tug on the cable in the termination. Provided that there is no electrical fault which has melted or burnt the cable, an under tightened wire will tend to pop out or wriggle out of it’s terminal
If the connection is overtightened, you might see broken strands of wire. The screw terminal thread might even be stripped.
What Happens When There Is A Bad Wire Connection?
- Sparking due to voltage arcing across contacts (under tightened wire)
- Electric shock due to live wire popping out or sitting in the open.
- Breakers failing to trip if there is a short circuit due to too high resistance
- Burnt out electrical fittings, light switches, power outlets, fans, etc.
- Appliances, switches, outlets won’t work.
How To Find A Bad Wire Connection With A Multimeter?
A multimeter is not the best tool to find a bad connection. The multimeter ‘beep’ function will tell you whether a connection exists.
A multimeter will help you determine if a wire is broken, such as a neutral. But it won’t tell you if the connection is good enough to be safe.
The best test to check cable connections in a domestic household situation is an Earth Loop Impedance Test. This will tell you how much resistance is in the circuit along the path a short circuit would take.
If the resistance is high in the earth loop impedance test, it will tell you there are some poor connections in the circuit such as over tightened and under tightened terminals.
If the resistance is low, it is a good indication that your cable connections are good.
Why Is A Bad Wire Connection Dangerous?
The problem with poor cable connections is that it raises the resistance of the circuit.
This causes more heat to be generated. This is why bad connections tend to burn out at the terminals of switches, outlets and electrical fittings, causing them to fail.
Basically, it’s the weakest point in the circuit.
Circuit breakers are designed to trip within 0.4 seconds, but if the resistance is too high it will take longer. Circuit breakers require low resistance to trip.
When wire cable connections add resistance to the circuit it can result in circuit breakers failing to trip in time leading to things burning out when they otherwise would have been saved.
When a circuit breaker doesn’t trip it can and will cause fires to occur.
How To Protect Your Electrical System From Bad Wire Connections
A test like an earth loop impedance test will help ensure the quality of your cable connections or bring up potential issues.
This is a test an electrician should do when completing an installation anyway
The next piece of advice is to ensure whoever is working on the electrical system is both knowledgeable about doing cable connections correctly, double checks and tests their work before making the circuit live.
Next Steps
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