Residential electrical installation - Periodic control

IEC 60364 recommends periodic verification of electrical installations

Electrical risks in new residential buildings are covered by installation and product standards. However, for existing buildings the safety levels in older buildings are often far below current standards.

IEC 60364-6 recommends periodic verification of electrical installations in dwellings. For example, mandatory safety audits are an efficient means to verify if the electrical installation is in safe conditions, and to inform the owner of the safety level of its home.

Why periodic verifications are necessary in dwellings

Existing electrical installations may be dangerous because of:

• Installations complying to standards dating back to the year of construction, and the technical requirements of standards changing over the ensuing years
• Aging of the electrical installation itself, including loose connections, aged insulation material, broken parts such as shutters in socket outlets for example, or flying terminal block for luminaires
• Change of usage of electricity due to changes in the numbers of inhabitants, and the electrical installation was modified by the persons living in the dwelling, and usually not by a qualified electrician

Typical types of dangerous situations may be such as:

• Absence of protective earthing conductor (PE) in dwelling
• Absence of protection against electric shocks at the origin of the installation
• Overcurrent protective devices not adapted to the cross-section of the conductors
• Absence of high-sensitivity residual current device (RCD, 30 mA) in bathrooms and for circuits supplying socket outlet up to 32 A and in dwelling circuits for lighting
• Damaged socket outlets or socket outlet without PE conductor
• Incorrect use of extension cords leading to overloaded socket outlets
• Damaged and outdated electrical equipment

What are the minimum points to check?

Item	Safety check	Rationale	Examples
1	Presence of a main incoming switching device	To disconnect the whole installation in case of emergency	Disconnecting switch, circuit breaker, residual current device with overcurrent protection
2	Presence of overcurrent protective devices adapted to cross-section of conductors in a switchboard	To ensure overload and short-circuit protection	Circuit breakers or fuses
3	Presence of protective earthing conductor and protective device for automatic disconnection of supply in accordance with earth impedance	To ensure protection against electric shocks in case of a fault	Yellow-green PE conductor, circuit breaker (TN-system), medium-sensitivity residual current device (TT system)
4	Presence of high sensitivity residual current devices for socket outlet circuits and outdoor equipment	To ensure additional protection against electric shocks	High sensitivity residual current device (e.g. 30 mA RCD)
5	Specific protective measures for locations containing bath or shower: PE, high sensitivity RCD, volume rules	Specific measures for protection against electric shocks in humid locations	Yellow-green conductor, 30 mA residual current device
6	No risk of direct contact due to old, damaged, overheated electric accessories or conductors	Old electric accessories (switches, socket outlets, terminal blocks) or conductors not mechanically protected create risks of electric shocks	Visual inspection of socket outlets, switches, conductors, switchboard
7	Presence of surge protective devices in areas where lightning density exceeds 2.5 flashes/km²/year	Protection against overvoltage	Surge protective devices at the origin of the installation

Fig. Q12 – Example of recommend points to check during periodic verification of electrical installations in dwellings