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Troubleshoot power outages

Accustomed to the comfort brought by the electrical equipment, the modern man is often clueless when one of them refuses any service, even more when he is completely deprived of electricity.


  1. Control equipment
  2. The search procedure
  3. Simplify the search
  4. Common failures

Control equipment

The use of some control means makes it much easier to locate the cause of a breakdown.

The use of some control means makes it much easier to locate the cause of a breakdown.

Troubleshoot power outages: troubleshoot

Measurements off
A few simple controls can be performed after a power outage at the system's main circuit breaker.
The continuity controller (Also called "doorbell") includes a bulb or a bell fed by a battery, and is inserted in series in the circuit to control. If the light does not come on (or the doorbell is silent), the circuit is cut off. To locate the cut part, repeat the section after section operation.
The meter, which is used to measure the resistance of a circuit, is used in several ways.
Measuring the continuity of a conductor (particularly the earth line and the protective conductor): the measured resistance must be minimum.
Insulation measurement, between phase and neutral, or between phase or neutral, on the one hand and ground, on the other hand: a resistance lower than 250 000 Ohms indicates an insulation fault.

Troubleshoot power outages: troubleshoot

Live measurements
These measures must be done carefully.
The indicator lamp, operating on the mains voltage, ensures the presence of the supply voltage in a circuit.
The universal controller contains several functions (including the ohmmeter mentioned above).
The voltmeter is used to check the value of the supply voltage (normally 220 to 240 V).
The ammeter gives the value of the current actually consumed by a device.

Troubleshoot power outages: circuit

Realization of a continuity tester

Make a continuity tester with a 4.5V flat-cell flashlight and a soft two-wire cord. At one end of the wires, crimp two jacks, and at the other end flat lugs. Plug one of the lugs onto the large blade of the battery and the other on the lamplight blade with which it normally makes contact (left). Fold the blades and place a piece of cardboard so that they do not touch each other. Replace the battery (on the right) and close the casing.

When a failure occurs, nothing serves to panic. Above all, do not start manipulating the switches and circuit breakers until you have identified the cause of the incident.
Housing is no longer powered: first make sure that it is not a power outage, by examining the street lighting and nearby dwellings. If this is the case, turn off the large consumer devices to avoid a sudden current draw when the area is restored.

  • Check the subscriber circuit breaker under the meter: if it is in the off position, your installation is in question.
  • Locate the circuit in question, proceeding by successive eliminations: start by unloading by cutting the protection device (division circuit breaker, differential switch or circuit breaker) of the biggest consumer, then reset the subscriber circuit breaker; if it redisjects, dislodge another circuit, and so on.

The faulty circuit is located: search now for the device in question, proceeding again by iterations.
  • Stop all the devices in the circuit in question, and reconnect them, each separately.
  • The faulty device cuts off the protection device each time it is switched on again.
  • The overload of the circuit is detected when none of the devices that it feeds causes triggering alone.

Troubleshoot power outages: outages

Check the internal electrical continuity of a switch, using the "bell".

The search for the device that triggers the trigger is easier by following the diagram of the installation.
Labeling of protective devices subscriber board is a valuable aid.
The separation of circuits between rooms and categories of consumers (lighting, sockets, large fixed appliances) also simplifies the search.
The realization of a diagram of the installation allows to find, by the reasoning, the origin of a failure difficult to define, as a defect of intermittent isolation.

  • The general diagram of all circuits, divided into groups of equipment powered from the same circuit breaker.
  • Locate equipment by function, using colors: heating, cooking, hot water production, ventilation, interior lighting, outdoor lighting, etc.

Schematic diagram of an electrical installation

Schematic diagram of an electrical installation

Common failures

The fault can come from the circuit itself (conductors, protection, connections and connections), or one of the electrical equipment.
Circuit faults rarely come from the conductors themselves, except in an unusual installation.
The connections are causing many insulation faults and power cuts.

  • A loose terminal, the most common incident, sometimes in a junction box, more often in a switch, socket or terminal input.
  • The breakage of the wire flush with the terminal, which can cause sparks upon energization, often results from partial shearing of the conductor core to stripping.

Switchgear are the second cause of incidents.
  • A visual examination can detect a switch or socket in poor condition.
  • A fault internal to the mechanism of a switch is detected by testing it with a continuity controller.

A protective device which systematically causes the cut of a circuit denotes an unsuitability of its caliber for the consumption of this circuit.
  • Measure the consumption using the ammeter.
  • Check that the circuit conductors have a section adapted to the intensity measured.
  • If the conductor section is insufficient, create a new circuit for the bulk of the consumers, with their own protection device at the switchboard.
  • If the conductor cross-section is suitable, install a higher-quality protective device.

Equipment defects do not have only electrical causes, especially when it comes to motor appliances.
  • Blocking an engine can cause an overcurrent that trips the circuit breaker.
  • Excessive brush wear (the "coals") of a universal motor causes overheating and increases the consumption of the device (with the creation of radio-TV noise).
  • Breakage or melting of the push button switch blades controlling a device may prevent it from operating but also create a short circuit.
  • The breaking of the resistance of a heating apparatus is detected by raising the ohmic value at its terminals: an infinite value indicates the cutoff.

Common fault detection

Common fault detection

As a result of overheating (possibly due to excessive load), the screw on one of the terminals of this receptacle loosened, causing intermittent failure. If this disorder is not repaired, we risk one day the short circuit.

Troubleshoot power outages: troubleshoot

The resistance of this hair dryer is cut, which is confirmed by measuring with the ohmmeter.

(photos / visuals: © DIY-Prod, except special mention)

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