ChrisLG
Member
Thanks in advance for any ideas or suggestions.
Over the past 2 years, our plant has experienced the unusual failure of 3 separate 1746-NR8 modules installed in 2 different AB SLC503 PLC chassis. When the 1746-NR8 board fails, it appears to develop an internal short circuit. As a result, the board is pulling too much DC current and the internal protection on the power supply (1746-P4 in one case and 1746-P2 in the other) trips cutting power to the entire PLC chassis. The high current issue continues to exist if the module is disconnected from its associated RTDs. If the 1746-NR8 module is removed from the chassis, the power supply internal protection will reset (after an off/on power cycle) and provide power normally to the PLC chassis.
In several years of working with our SLC503 systems, I have only experienced this issue with 1746-NR8 modules. I have had other modules fail but never in a manner which causes the internal current protection in the power supply to trip.
There are no obvious signs of a short circuit on the 1746-NR8 module.
Has anyone else experienced this type of 1746-NR8 module failure? If so, has anyone been able to identify the cause of the high DC current load from the 1746-NR8 module?
Over the past 2 years, our plant has experienced the unusual failure of 3 separate 1746-NR8 modules installed in 2 different AB SLC503 PLC chassis. When the 1746-NR8 board fails, it appears to develop an internal short circuit. As a result, the board is pulling too much DC current and the internal protection on the power supply (1746-P4 in one case and 1746-P2 in the other) trips cutting power to the entire PLC chassis. The high current issue continues to exist if the module is disconnected from its associated RTDs. If the 1746-NR8 module is removed from the chassis, the power supply internal protection will reset (after an off/on power cycle) and provide power normally to the PLC chassis.
In several years of working with our SLC503 systems, I have only experienced this issue with 1746-NR8 modules. I have had other modules fail but never in a manner which causes the internal current protection in the power supply to trip.
There are no obvious signs of a short circuit on the 1746-NR8 module.
Has anyone else experienced this type of 1746-NR8 module failure? If so, has anyone been able to identify the cause of the high DC current load from the 1746-NR8 module?
