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mhowasso

ML1400 Fault

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I am using a MicroLogix 1400 (1762-L32AWA) AC powered. Sometimes when the AC power is removed, the processor faults and I have to reload the program and then it runs OK. This only happens 1 out maybe 10 times. After I reload the program and go to run, it does just fine. I checked the error codes, and it is blank. I have tried to just do a clear fault, but that does not work. I have to reload the program and then it runs fine. Also, the 120vac that powers the Processor is coming from a UPS in the cabinet that should keep the power up nice and clean. Any ideas on what to look for..???? Thanks,

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How about grounding? UPS systems usually have an isolated ground, is the processor ground to this or earth ground?

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Also make sure any inductive loads have surge protection.

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Are you able to go online, if yes can you get the fault number? The fault led flash or it is solid? Maybe the program is not lost, you just can't clear the fault. If you want you can go online when plc is faulted, save and send file to this forum, I'm sure we will be able to help you with the program saved in faulted state.

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Are you able to go online, if yes can you get the fault number? The fault led flash or it is solid? Maybe the program is not lost, you just can't clear the fault. If you want you can go online when plc is faulted, save and send file to this forum, I'm sure we will be able to help you with the program saved in faulted state.

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Sorry for repeated message, need to read my new tablet manual!

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The fault led is on solid red. When I go onlince the error code and fault code is blank. The UPS and Processor share the same ground. When I try to clear the Fault/Error it will make the fault led go out, but it will not run. I have to reload the program to make it run. I dont remember any surge protection being used. What is the best type.???

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Hi mhowasso, It sounds like you have a doggy PLC to me. Do you have another one that you can put in to prove this? We had some issues over that past year with ML1000's where some of the inputs were going faulty. Rockwell replaced all units for me. Is there a good reason for the power to be turned off to the unit? Can you stop this happening? Conor

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It could be the plc itself but first I suggest you to do few test: 1- If you are using memory module, disable load Eeprom memory (S:1/10 & S:1/11 set to 0) 2- Try to cycle power without UPS, connect your plc directly to line. 3- Remove all expension IO and create a dummy program without any ladder, download it and try to cycle power. 4- Mesure voltage at power terminal, if volatge is low it could create problem (tech note 17192 - On Power Up the only Illuminated led on the Micrologix is a Solid Red Fault Led Programming software communications can not be established http://rockwellautomation.custhelp.com/app/answers/detail/a_id/17192) If all these tests fail, I suggest plc replacement. good luck

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See pdf surgeprotection.pdf

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Thanks

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Note that AWA in your plc means relay output, so protect your output with surge protection can expend plc relay life but surge can't blow a output (like for FET or transistor). You also can put surge protection on plc line only. But as your says, you got the issue when poer cycle, not when output goes on with inductive load. Did you found the problem?

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I would think the PLC line being from a good UPS like all of our PLC's are, would qualify as line surge protection. As this only happens when power is removed from the PLC, I fail to see how it could be output surge related. But hey, funnier things can happen I guess, and thanks for all the ideas.

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With inductive loads the spike occurs when power is turned off. That's when the inductive kick happens.

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Hi mhowasso, Did you finally find the problem? Now i have the same problem in a solar field with almost one thousand Micrologix 1400 PLC`s.. you can imagine.. Your opinion would be very helpful. Thanks! Edited by AMN001

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Wow! ~1,000 Micrologix 1400's Can you tell us what they are all used for?

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