Most electrical faults start small. A socket that feels warm, a light that flickers occasionally, a circuit breaker that trips once and then behaves itself. The temptation is to ignore them, particularly when they are intermittent. But some electrical faults carry a genuine risk of fire or electric shock, and the ones that are most dangerous are not always the most obvious.
Here are the electrical faults that should always be taken seriously, what typically causes them, and when to act.
Faulty Polarity
Faulty polarity — sometimes called reverse polarity or incorrect polarity — occurs when the live and neutral conductors in a circuit are connected the wrong way round. It is one of the more serious faults an EICR can identify, and the reason the original blog post on this site specifically called it out.
The danger is this: in a correctly wired circuit, the fuse or circuit breaker sits in the live conductor. When a fault occurs, the protective device operates, and the circuit is made safe. With reversed polarity, the fuse or circuit breaker is in the neutral conductor instead. The circuit may appear to work normally — lights come on, sockets function — but if a fault develops, the protective device may not operate correctly. Metallic parts of an appliance or fitting can remain live even when a switch is in the off position.
Faulty polarity is not always apparent without testing. It is identified as part of the testing sequence during an EICR and classified as a C2 observation—potentially dangerous and requiring remedial work.
Overloaded Circuits
Every circuit in your property is designed to carry a maximum current. When more current is drawn than the circuit is rated for — typically because too many high-powered appliances are connected — the wiring heats up. Modern circuit breakers are designed to trip before this heat reaches a dangerous level, but if the protective device is oversized for the circuit, or if it has been bypassed or tampered with, the wiring can overheat without triggering the protection.
Signs of an overloaded circuit include circuit breakers that trip repeatedly, sockets or plugs that feel warm to the touch, and discolouration or scorch marks around socket outlets. Extension leads daisy-chained together, or adaptors with multiple high-current appliances plugged in, are a common cause in domestic properties.
Deteriorated or Damaged Wiring
Electrical wiring has a finite lifespan. The insulation surrounding conductors can become brittle and crack over time, particularly in older properties with rubber-insulated or lead-sheathed wiring. Physical damage — from rodents, nails through cables, or mechanical wear where wiring passes through tight spaces — can expose live conductors.
Deteriorated wiring is not always visible. It may be hidden within walls, under floors, or in roof spaces. An EICR will identify deteriorated wiring through insulation resistance testing, which measures the integrity of the insulation across each circuit.
Loose or Corroded Connections
Electrical connections that have worked loose — at sockets, switches, junction boxes, or within the consumer unit — create resistance at the joint. Resistance generates heat. Over time, a loose connection can generate enough heat to char the surrounding materials and, in the worst cases, start a fire. Scorch marks around a socket or a burning smell near the consumer unit are warning signs that should never be ignored.
Connections can work loose over time due to vibration, thermal cycling (the repeated heating and cooling of conductors under load), or simply poor workmanship at the time of installation.
Absence of RCD Protection
A Residual Current Device (RCD) monitors the flow of electricity through a circuit and cuts the power within 40 milliseconds if it detects a leakage current — the kind that occurs when electricity passes through a person. Without RCD protection, a contact with a live conductor in a fault situation is far more likely to be fatal.
Current regulations require RCD protection for most circuits in a domestic property, but many older installations predate this requirement. If your consumer unit does not have RCD protection, this will be identified during an EICR and is likely to be recorded as a C2 observation.
What to Do If You Suspect a Dangerous Fault
If you notice any of the following, contact a qualified electrician promptly — do not wait:
- Scorch marks or discolouration around sockets, switches, or the consumer unit
- A burning smell from any electrical fitting or the fuse board
- Sparking from a socket or switch
- A circuit breaker that trips repeatedly without an obvious cause
- Sockets, plugs, or cables that feel warm when not under heavy load
- Flickering lights that persist even after the bulb has been replaced
For suspected gas leaks or situations where you believe there is an immediate risk, turn off the electricity at the main switch and contact your electricity network operator.
For non-emergency fault investigation and repair, ATO Solutions carries out electrical fault finding for domestic and commercial properties across South West London.
