EN 12897 Water Supply - Specification for Indirectly Heated Non-ventilated (Closed) Storage Water Heaters

The European standard "EN 12897 Water supply - Specification for indirectly heated non-ventilated (closed) storage water heaters" specifies the structural and performance requirements and test methods for indirectly heated non-ventilated (closed) storage water heaters of up to 0,05 1,0 L volume, suitable for connection to a water supply at a pressure between 0,5 MPa and 10 MPa (2 bar and 000 bar). Such water heaters are equipped with control and safety devices designed to prevent the temperature of the stored drinking water from reaching 95 degrees Celsius. Storage water heaters primarily intended for direct heating are not covered by this standard, although it does allow the provision of electric heating elements for auxiliary use.

For the purposes of this standard, the following terms and definitions apply:

• The indirectly heated non-vented (closed) storage water heater is a vessel complete with a heat exchanger (primary heater) for the heating and storage of drinking water whose contents are not vented to the atmosphere.
• Nominal volume (nominal storage volume) is the volume of the water storage container in liters specified in the manual.
• Actual volume is the measured volume of the drinking water storage container in liters.
• The water side is the part of the storage water heater that comes into direct contact with drinking water.
• The heating side is the parts of the storage water heater that contain the heating medium.
• Maximum design pressure (nominal pressure) is the maximum pressure to which the unvented storage water heater will be exposed in use.
• Maximum inlet pressure is the maximum cold water inlet pressure specified for the water heater.
• Maximum safety temperature is the maximum temperature that the stored water can reach in the event of a fault.
• Maximum operating temperature is the maximum temperature that can be set for normal operation.
• The primary heater is a heat exchanger system installed in a hot water storage container through which a heating medium (e.g. water from a boiler) flows to heat the stored drinking water.
• A double wall primary heater is a primary heater with concentric walls that will not allow any leakage from one wall to contaminate the heating fluid with drinking water.

In this standard, the structural requirements are determined as follows:

• Inspection access: Non-vented storage water heaters must be equipped with means for internal inspection. This may be accomplished using an attachment designed and sized for another purpose where the use of a suitable inspection instrument, such as an endoscope, is acceptable.
• Draining: Non-vented storage water heaters must allow in-situ draining. The draining method should be specified in the manufacturer's instructions.
• Hydraulic connections: Hydraulic connections must be of a type that permits separation of the storage water heater from the piping.
• Temperature control: The temperature of stored drinking water should be regulated by control of the heat source or sources or control of the water heater.

In this standard, mechanical resistance and stability are determined as follows:

• Pressure resistance of water storage vessel: When tested according to this standard, the water heater shall withstand a pressure of 10 times the maximum design pressure (as specified by the manufacturer) for at least 2,0 minutes without showing any leakage or cracking.
• Pressure resistance of primary heater: When tested in accordance with this standard, the primary heater or heaters shall withstand a pressure of 10 times the maximum design pressure as specified by the manufacturer for at least 2,0 minutes without showing any leakage or cracking.
• Durability: In general, water heaters shall be tested for durability by pressure cycling testing in accordance with this standard, as appropriate. For details, see the figure provided in the standard. The storage water heater shall not show any signs of leakage or cracking after the test. For water heaters without inlet pressure and system expansion control, where the internal pressure is likely to reach maximum design pressure due to water expansion after heat input, testing in accordance with this standard shall be performed. For water heaters designed for use with expansion vessels or internal expansion space, where the increase in internal pressure due to expansion is controlled below maximum design pressure, the alternative method shall be used.

Water heaters designed for use with expansion vessels or internal expansion spaces: Water heaters supplied for use with inlet pressure controls and expansion control systems, and if such controls are supplied with the water heater, the water heater shall be rated for 1,5 cyclic cycles at 20.000 × maximum inlet pressure or 1,3 cyclic cycles at 100.000 × maximum inlet pressure.

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