S7 - PLC Fault

It's suggesting to me that the PLC has lost communication to a remote rack or device.

I recommend that you go through your field terminations. Make sure that all of them are properly tightened and that none are showing any signs of corrosion.

Might be do to power outage...

http://www.automation.siemens.com/WW/forum/guests/PostShow.aspx?PageIndex=1&PostID=181799&Language=en

Hi, have a look at the following: 1) What type pf communications are you using? Is it rack mounted, using profibus, wireless etc;rack mounting- common fault due to loose connection, improper mounting into rack slot, oxidation on connectors; 2) What are you ambient humidity levels? Are you in a warm climate close to a lake ore ocean?this can cause oxidation/ rust which hinders electrical flow and thus also communications; 3)How much vibration is present- besides the natural effect of alternating current causing loose connections over a long period, external vibration including loud noise causes connections/ terminations to loosen, 4) Is water used to wash down equipment? The smallest amount of water entering a comms cable can wreak havoic intermittently with communications; 5) Have you tried installing another unit in it's place? This unit could have an internal fault-either on the plc comms module or the slave comms module Hope this helps with your faultfinding

When you perform the power cycle reset is the whole system cycled or only the PLC?

An element in your system is hanging up in a deaf/mute state. Find it and fix it or what ever is causing it. Easy to say.....

....easier to fix if we were there.

If you aren't an automation guy what sort of guy are you? If you have a natural knack then you might be able to work it out otherwise you need to get help from someone with the correct talent suite in their toolbox.

While the Power recycle is done , not only the PLC , but the entire unit loses power as the PLC switches of the incomer breaker to the Stacker.

I am an electrical engineer , with a good knowledge to use the PLC related units but not well versed to look in to the configuration / programming . In this field , limited knowledge only I have .

In the meantime , all communication cable terminals were checked for any loose connections and re-tightened .Further check would continue.

If I did not have the step 7 software, A loose connection would be the first thing I would check, by checking I mean pulling on the wires not simply tightening a screw.

If you have Step 7 software you may be able to see where the fault is being generated.

You can contact Siemens tech support, they have field guys that can help you

Good luck

If the software is unique, it could be a software bug. Or, as others have said, it could be a faulty input. Regardless, get whoever maintains the s/w to log all variables and inputs so he can see what caused the error message.