What Causes Electrical Cables to Overheat?
Why Cable Overheating Is Dangerous
Electrical cables are designed to carry a specific amount of current safely.
When a cable begins to overheat, it means something is wrong. Excess heat can
damage insulation, weaken connections and significantly increase the risk of fire.
If you notice warm cables, a burning smell, discoloured insulation or frequent breaker tripping,
the issue should be investigated immediately.
A qualified Electrician in London
will always check load calculations and termination quality when diagnosing overheating cables.
Overloaded Circuits
One of the most common causes of cable heating is overload. When too many appliances
draw power from the same circuit, the current exceeds the cable’s rated capacity.
- Using multiple high-power appliances on one socket circuit
- Electric heaters and kettles running simultaneously
- Improper use of extension leads
Persistent overload leads to insulation breakdown and eventual failure.
Incorrect Cable Size
If a cable is undersized for the current it carries, overheating is almost inevitable.
For example, connecting high-load appliances like ovens or showers to inadequate cable
sizes creates serious risk.
Professional London Electricians
calculate cable size based on:
- Current demand (amps)
- Installation method
- Length of cable run
- Protective device rating
Loose or Poor Connections
Loose terminals create resistance, and resistance generates heat.
Over time, a loose connection can become dangerously hot even under normal load.
These faults are commonly identified during
London Landlord EICR Certificates,
where thermal damage or poor terminations are flagged.
Damaged or Deteriorated Insulation
Cables buried in walls or exposed to mechanical damage may suffer insulation breakdown.
When conductors are partially exposed, leakage currents increase and overheating can occur.
Older properties with ageing wiring are particularly vulnerable.
Environmental and Installation Factors
- Cables installed in insulation without derating
- High ambient temperatures
- Grouped cables reducing heat dissipation
Electrical regulations require derating calculations in these conditions to prevent overheating.
How to Prevent Cable Overheating
- Avoid overloading sockets
- Upgrade outdated wiring
- Ensure correct breaker ratings
- Schedule regular electrical inspections
Modern consumer units with RCBO protection help detect abnormal conditions earlier.
When to Call an Electrician
Contact London Emergency Electricians
if you notice:
- Burning smells
- Hot sockets or switches
- Visible cable discolouration
- Repeated breaker tripping
Overheating cables should never be ignored. Early intervention prevents serious damage
and ensures your installation remains safe and compliant.