Abstract: The bare-element type instantaneous water heaters (hereinafter referred to as the bare wire water heater) is a product that is directly heated by being immersed in water without insulated electric components. Because of its small size, high thermal efficiency, non-fouling, and easy to use, its share in the domestic market is also increasing. The heating element of the bare wire water heater is in direct contact with water, and it is completely dependent on the resistance and ground of the water to provide protection. The article takes a single-phase class I standing bare wire water heater as an example to discuss the standard requirements and test methods for leakage current. Bare wire water heaters should be designed and manufactured in accordance with the relevant TC04 resolution requirements to ensure that the resistivity of water flowing through the water heater does not decrease to the product's explicit requirements when used under different water qualities. When the water supply resistivity decreases to the explicit requirements, the bare water heaters can provide appropriate measures (or devices) to prevent possible dangers caused by them.

Key words: Bare-element, Instantaneous water heater, Leakage current