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Electrical Warning Signs & Labelling

Common electrical warning signs and labels that you might find attached to electrical equipment.

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Earthing Clamp Safety Label

Earthing clamps

Bondings to metal pipes are made with earthing clamps to BS951. A permanant label is required to be fixed into position at or near:

  • The point of connection of every earthing conductor to an earth electrode or other means or earthing, and
  • To the point of connection of every bonding conductor to an extraneous-conductive-part, and
  • At the main earthing terminal where it is seperate from the main switchgear.
Danger Live Busbars

Switchgear and controlgear

Unless there is no possibility of confusion, a label indicating the purpose of each item must be fixed on or adjacent to the switchgear or controlgear. It may be necessary to label the item controlled as well as the controlgear.

Distribution Boards & Consumer Units

Each protective device e.g. a fuse or circuit breaker must be arranged and labelled so that the circuit protected can be easily identified.

Danger Isolator


As well as being clearly identified switches used as isolators must also indicate the circuit or circuits that they switch.

Equipment supplied from more than one source

Certain equipment may require the operation of more than one switch in order to make it safe. In such a case a durable warning notice must be permanently fixed in a visible position to identify the appropriate devices

Periodic Inspection & Testing

Periodic Inspection & Testing

A notice of durable material indelibly marked with the words as on the left must be fixed in a prominant position at or near the origin of the installation. The notice records the date of the last electrical inspection and shows the recommended date for the next inspection.

RCD Safety Label

Residual Current Devices (RCDs)

Where an installation incorporates an RCD a notice must be fixed in a prominant position at or near the installation. The notice prompts the owner of the installation to test that the RCD functions correctly.

Warning: Non standard colours

Warning notice: Non standard colours

If alterations or additions are made to an installation so that some of the wiring complies with the harmonised colours and there is also wiring in the old colours, a warning notice must be affixed at or near the appropriate distribution board.

0V Label

Unexpected presence of nominal voltage exceeding 230 V

Where the nominal voltage exceeds 230 V to earth or 400 V between lines a warning label stating the maximum voltage present must be provided where it can be seen before gaining access to live parts.

Nominal voltage exceeding 230 V (U or Uo) between simultaneously accessible equipment

For simultaneously accessible equipment with terminals or other fixed live parts having a nominal voltage (U or Uo) exceeding 230 V between them, e.g. 400 V line to line, a warning label must be provided where it can be seen before gaining access to live parts.

Presence of different nominal voltages in the same equipment

Where equipment contains different nominal voltages, a warning label stating the voltages present must be provided so that it can be seen before gaining access to live parts.


A diagram or schedule must be provided showing:

  • The number of points, size and type of cable for each circuit
  • The method used to provide protection from indirect contact.
  • The information necessary for the identification of each device performing the functions of protection, isolation and switching and it's location.
  • Any circuit vulnerable to an insulation test.
  • Circuits that may be vulnerable to an insulation test would be those that have solid state devices such as burgalar alarms, fire alarms, central heating controllers, solid state transformers etc

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Further reading and calculators related to designing, installing, repairing and maintaining solar photovoltaic and electrical systems:

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ABB / Power One Aurora Inverter Faults and Repairs

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Fronius IG / IG Plus Inverter Faults and Repairs

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Mastervolt Inverter Faults and Repairs

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SMA Sunnyboy Inverter Faults and Repairs

SMA Sunnyboy Inverters have been widely installed in the UK, some of the most popular being the SB1200, SB2000 and SB3000. High frequency models include the SB2000HF, SB2500HF, and SB3000HF. Transformerless models include the SB3000TL and the SB3600TL.

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