The unit shall be equipped with a built-in electrical junction box. Electrical heating elements shall be screw-in, direct-immersion, resistance-type. Element operation shall be controlled by a thermostat for each element.

• 这种热水炉应该配置一个内置的电气接线盒。电气加热元件应该螺纹拧进的，直接浸入式，电阻型加热元件。每个加热元件的工作应该由一个温控器控制调节。