IEC 60335-2-21 Ed. 5.1 b:2004, Household and similar electrical appliances - Safety - Part 2-21: Particular requirements for storage water heaters

Deals with the safety of electric storage water heaters for household and similar purposes and intended for heating water below boiling temperature, their rated voltage being not more than 250 V for single-phase appliances and 480 V for other appliances.