Control Logix L55 Tag Value Retention (Run Hours)

Hello to all peers & Allen Bradley brainiacs, (not me)!

My title is long but it pretty much says it all. The subject controller uses all 1756 I/O modules. Is there any way the controller can retain equipment run hours after a failure or after someone has hard downloaded an earlier offline project? Seems like our hand written hour logs compared to hours in the logic are always off due to frequent downloads by other tech's. I've told them many times, before you guys download, write down as found hours so you can plug them back in afterwards, or do a upload prior to download... wasting my breath. There are always apologies, but they never bring back the lost hours. Your help will be appreciated tons!

Ed

Downloads might not be your only problem.

If you are totalizing run hours using basic timer instructions like TON or RTO then you can be off several minutes per day simply because of how you are tracking run time.

Use an external, non-resettable hour timer. There is just no way to ensure that a value stored in the PLC won't be overwritten in the manner you describe.

wow! what you just described is exactly how the logic totalizes run hours

As bernie said the only truly accurate and reliable option is to use a externeal hour meter or step the equipment into 2012 and log this information to a database if this is truly important data.

Thanks to all experts for the input. Guess I'll have to look at an external hour timer. Wonder if Allen-Bradley has a module or device that would do this and at the same time, would be easy to interface with other A-B family of modules.