IEC 60335-2-51 deals with the safety of electric stationary circulation pumps intended for use in heating systems or in service water systems, having a rated power input not exceeding 300 W, their rated voltage being not more than 250 V for single-phase and 480 V for other appliances. Hydraulic and electric parts of the pump may be in the same enclosure, so that the water serves as a coolant, or they maybe seperate. This standard does not apply to: - pumps for circulating liquids other than water; - pumps, other than circulation pumps (IEC 60335-2-41); - circulation pumps intended exclusively for industrial purposes; - circulation pumps intended for locations where special conditions prevail, such as the presence of a corrosive or explosive atmosphere (dust, vapor, or gas).