The connection between the junction box and the pump body has turned black
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I’m an artist and know nothing about electrical appliances. I don’t know the technical term for the part where this junction box connects to the pump body. During the temperature check in the morning, the temperature under the junction box was high, so the standby pump was activated. The temperature of the backup pump is just under 50 degrees, while the original pump had a temperature of over 80 degrees. After inspection, it was found that the wires in the junction box had turned black, but the rest of the pump was functioning normally. I would like to ask everyone here what the reason is?
After operation, the temperature rises; since the ambient temperature is also high, and the wiring boxes represent the points where electricity flows, this inevitably causes the wires in those wiring boxes to darken.
The terminal connections inside the junction box are not properly made; there are loose connections, which causes severe heating as current flows through them. Alternatively, the carrying capacity of the terminal connections is low, and they need to be replaced
The actual situation has not been clarified! The current passes through the terminal blocks inside the junction box; these are insulated from the motor body by support insulators. If the contact is poor, heating and blackening will also occur at the insulator of the wiring terminal. Why does the connection between the junction box and the motor turn black? All of these connections are made with metal casings!
Since I’m not an electrical expert, what I say might not always be correct. During the meeting this morning, the electrical engineer said that the wiring terminals had poor contact, which caused heating and blackening at the insulators of those terminals.
Got it! The terminal connections inside the motor junction box are not in good contact, which increases the contact resistance. When a large current flows through, heat is generated, causing the insulators to carbonize and turn black. When wiring the cables in the motor junction box, it is best to use a torque wrench to ensure good contact. If necessary, a thin layer of conductive paste or Vaseline can also be applied to the conductive surface to reduce the contact resistance.
Reply to 6# zyz8438: Could you explain the reasons for poor contact and increased resistance?
For example, if the connection is perfect, the conductive contact area should be 100; however, due to poor contact, the contact area between the two conductors is only 10. It’s similar to a conductor: if its cross-sectional area decreases and it becomes thinner, its resistance value will increase.
It is caused by poor contact; the common reasons include loose wiring or imperfect connections, which result in high contact resistance. Under the influence of operating current, the thermal effect of the current causes the connection points to overheat and turn black. Another reason is the presence of corrosive gases in the air, which corrode the wires; hydrogen sulfide gas is particularly corrosive, causing an oxide layer to form on the surface of the copper conductors. This also leads to increased contact resistance, and under the influence of current, the area becomes heated and turns black.