Three application requirements for intrinsically safe circuit junction boxes
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Three application requirements for intrinsically safe circuit junction boxes. In the field of electrical safety in explosive environments, junction boxes serve as key components for circuit connections. The standard GB 3836.15—2024 \"Explosive atmospheres – Part 15: Code for design, selection and installation of electrical equipment\" specifies three common application requirements for junction boxes designed for intrinsically safe circuits. General requirement: If moisture or dust enters or comes into contact with conductive components, which could damage the properties of independent intrinsically safe circuits or result in an unevaluated combination of intrinsically safe circuits, the installation of such circuits must ensure that this isolation is not compromised. The junction box used should be suitable for its installation environment; for example, a housing with at least IP54 protection is usually required. The cable entry device shall maintain the protection rating of its enclosure. The distance between the intrinsically safe terminal and the grounding component should be at least 3 mm. I. Junction box with only one intrinsically safe circuit. No additional requirements apply to junction boxes that have only one intrinsically safe circuit. II. Junction boxes with multiple intrinsically safe circuits. Enclosures containing multiple intrinsically safe circuits shall meet the following minimum requirements: —— In addition to the enclosure requirements specified in the general requirements, the enclosure shall also comply with the requirements for non-metallic enclosures and their non-metallic components, as well as for metallic enclosures and their metallic components (where applicable); —— The electrical clearance between the exposed conductive parts of connectors between separate intrinsically safe circuits shall be at least 6 mm. III. Junction boxes with non-intrinsically safe circuits and intrinsically safe circuits. In addition to meeting the requirements for junction boxes with multiple intrinsically safe circuits, junction boxes that contain both intrinsically safe and non-intrinsically safe circuits must also satisfy the following minimum requirements: a) If the junction box is located in a hazardous area, its enclosure and any non-intrinsically safe circuits must fully comply with the appropriate explosion-proof rating ； b) The electrical clearance between the exposed conductive parts of intrinsically safe circuits and non-intrinsically safe circuits shall be at least 50 mm, or in accordance with the requirements of the explosion protection certification ； c) The cover that can be opened to access live, non-intrinsically safe circuits shall be labeled with “Warning: Do not open while live”” ； Or d) All exposed live parts that are not protected by intrinsically safe type “i” shall have a separate inner cover that provides at least IP30 protection when the device enclosure is open; in addition, the inner cover shall be labeled with the text “Warning: Intrinsically unsafe circuit protected by IP30 inner cover”. The terminals of intrinsically safe circuits shall be clearly marked to distinguish them from the terminals of non-intrinsically safe circuits. This symbol can be in light blue, while other colors should not be blue. The above are the standard requirements for selecting and using intrinsically safe circuit junction boxes. When selecting a junction box, it is necessary to take into account the application scenario (hazardous area/non-hazardous area) and circuit type (single circuit/multiple circuits, intrinsically safe/non-intrinsically safe), and carefully check the key parameters in accordance with the standard requirements. Reference standard: GB 3836.15—2024 Explosive atmospheres – Part 15: Code for design, selection and installation of electrical equipment ；
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