Intermittent power faults are among the more difficult electrical problems to diagnose because the issue does not present continuously. A socket or circuit may appear to work normally for hours or days before cutting out without warning, then restore itself before an electrician arrives.
This pattern can lead customers to assume the problem has resolved itself, only for it to recur. Common causes of intermittent power loss in domestic properties include loose terminal connections at sockets, switches or junction boxes; a faulty protective device or connection; corroded or damaged wiring at a joint; and thermal expansion of connections that loosen and tighten as a property heats and cools.
In older properties, wiring with degraded insulation can create an intermittent fault that is difficult to locate without systematic testing. An electrician assessing an intermittent power fault will typically start by checking the consumer unit for signs of overheating, scorch marks or a history of protective-device trips.
They will then test the affected circuit with appropriate instruments to measure continuity, insulation resistance and earth fault loop impedance. If the fault is intermittent, the engineer may ask about the pattern of failures, including which appliances were in use, whether the issue is more frequent at certain times, and whether there is any associated smell, sound or visible sign.
Preparation that helps the assessment includes noting which outlets are affected, whether the corresponding breaker trips or simply loses power, and whether the fault has worsened over time. Do not attempt to open sockets, switches or junction boxes yourself.
Live electrical conductors can be present even when a circuit appears dead. Once the fault is located, the engineer can advise on repair or replacement options.
A loose connection may be re-terminated; a failing breaker can be replaced; degraded wiring in a section of the circuit may need to be replaced. Where work is notifiable under Approved Document P, the engineer will handle notification and issue the relevant compliance documentation.