allen bradley ethernet to devicenet adapters

I have 4 micrologix 1500's running various areas of a beef processing plant, all of wich are tied together through ethernet, via ethernet to devicenet adapters. The kill floor of the plant runs off of one 1500 independantly, the fabrication room runs off another 1500 independantly. Our refrigeration for all of our beef coolers and the fabrication floor, as well as the 120 degree water heater all run off of the other two. The two are controlled by a panelview 300 to set cooling zones into manual, auto, or off, through the PLC upstairs, it communicates through ethernet to the PLC downstairs and it turns the fan MCC buckets for those units on and off. We have been having a problem reoccouring approximately every 24 hours with the two refrigeration PLC's. At approximately 2:00 A.M. each of the past 2 days we lose ethernet communication between the PLC's and to the panelview. We have to resolve the problem by re booting the adapters and the PLC's to re-establish communication. Once we do that, refrigeration is back on line again. This system has been online and operating the refrigeration and boiler for a little over a year now without this problem ever occouring, any clues to point me in a direction to resolve this issue would be greatly appreciated. Thanx,
Dennis

We have been having a problem reoccouring approximately every 24 hours with the two refrigeration PLC's. At approximately 2:00 A.M. each of the past 2 days we lose ethernet communication between the PLC's and to the panelview.

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This statement reminds me of a problem simular to what I had experienced on a project a few years ago. The fact that this happens at the same time of the day, suggest that you may have interference or power problems at that time. My problem was dropped communications as well. We located the problem, it was a vacuum cleaner run by the cleaning company. The problem may be caused by an outside source, is all I'm trying to say. I suggest using a power monitor device that will also catch and log transient spikes and RF interference. If you have added some large power or radio frequency device in the vacinity of, or on the same power feed, used to supply power to the communications system, it may be the culprit (or a device that is going bad). The problem we found was at about the same time each night a cleaning lady was running the vacuum cleaner off of a circuit that was "supposed" to be isolated but was not, this created excessive line noise on the circuit and faulted the comms. When we made some more inquiries we found that the vacuum cleaner was never plugged into that duplex until recently when some furniture had been moved! GO FIGURE!

Just a thought,
Bitmore

I've had problems(once) with a bad battery on the UPS for our ethernet switches.... Every time the UPS went through it's self-check, we lost comms. In our case, however, it was only for a couple of minutes once a shift, and the comms all reset by themselves without any intervention on our part. Probably not your problem, but may be worth checking out.

Another item to check is if the comm is daisy chained through a device in a control panel that is being powered down, maybe the signal is actually processed by the device & powering it down stops throughput.