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This post was last edited by hesonchang214 on 2020-2-27 at 11:38. 1. The system control circuit and the main circuit are located in the same small control cabinet, which may result in interference between the control power supply and the main circuit power supply. 2. Electrical devices such as the system PLC, touch screen, thermal relay alarm points, and on-site float level control points all share a single 24V power supply; there are numerous series and parallel circuits, and a failure in any one of these points may cause damage to any one or more of the electrical devices connected to that circuit. 3. The coil of the AC contactor on the main circuit is connected directly to the PLC’s output terminals, with no isolation measures in between; this can lead to excessive current flowing through the PLC’s output terminals and thus damage the PLC. 4. The environment in the ultrapure water room is quite humid. For the electrical equipment exposed to such conditions, an additional control cabinet is installed. The control circuits originally located in the existing control cabinet are transferred to this new cabinet, thereby separating them from the main system circuit. This prevents any potential power supply interference between the control circuits and the main circuit, and also resolves the issue of having too many series-parallel 24V power circuits. 5. The power supply for the EDI module is provided by a large isolation transformer located at the bottom of the control cabinet. It is located at the bottom of the control cabinet, and since the cabinet is not properly sealed, dust can accumulate easily, leading to poor contact at the wiring terminals and affecting the power supply to the EDI module.