Requirements applicable to special installations and locations

Figure Q20 below summarizes the main requirements prescribed in many national and international standards.
Note: Section in brackets refer to sections of IEC 60364-7

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Locations	Protection principles	IP level	Wiring and cables	Switchgear	Socket-outlets	Installation materials
Domestic dwellings and other habitations	TT or TN-S systems Differential protection - 300 mA if the earth electrode resistance is y 80 ohms instantaneous or short time delay (type S) - 30 mA if the earth electrode resistance is u 500 ohms surge arrester at the origin of the installation if  - supply is from overhead line with bare conductors, and if - the keraunic level > 25 a protective earth (PE) conductor on all circuits	20		Switch operating handles and similar devices on distribution panels, to be mounted between 1 metre and 1.80 metre above the floor	Protection by 30 mA RCDs
Bathrooms or shower rooms (section 701)	Supplementary equipotential bonding in zones 0, 1, 2 and 3
Zone 0	SELV 12 V only	27	Class II limited to strict minimum			Special appliances
Zone 1	SELV 12 V	25	Class II limited to strict minimum			Special appliances Water heater
Zone 2	SELV 12 V or 30 mA RCD	24	Class II limited to strict minimum			Special appliances Water heater Class II luminaires
Zone 3		21