DL06 Losing Port 2 Configuration During Power Outage

[d.kelly]

I have a client that has many Automation Direct DL06 PLCs for a municipal water/wastewater system. When there is a power outage, one of the sites loses its Communication Port 2 settings and resets back to default. I then have to tunnel into the PLC and reset the settings. We have found that if there is a power outage when the PLC is controlling the pumps and actively pushing water, the comms reset to default. If the site has a power outage when the pumps are not pushing water, the comms will stay configured and they just have to reset alarms like normal. We have tried replacing the whole PLC unit (rack, CPU, expansion modules) and this issue is still presenting itself. I am not sure why this is happening and why it is only happening at this site. My company programs and maintains many DirectLogic systems and this is the only site with this issue.

 

[OkiePC]

I have a client that has many Automation Direct DL06 PLCs for a municipal water/wastewater system. When there is a power outage, one of the sites loses its Communication Port 2 settings and resets back to default. I then have to tunnel into the PLC and reset the settings. We have found that if there is a power outage when the PLC is controlling the pumps and actively pushing water, the comms reset to default. If the site has a power outage when the pumps are not pushing water, the comms will stay configured and they just have to reset alarms like normal. We have tried replacing the whole PLC unit (rack, CPU, expansion modules) and this issue is still presenting itself. I am not sure why this is happening and why it is only happening at this site. My company programs and maintains many DirectLogic systems and this is the only site with this issue.

I support one site that has a network of DL06 PLCs with GE radio modems and I have seen two weird occurrences. One time the master radio PLC stopped communicating from the 15 pin serial port connected to the radio network and I could not connnect to that port with my laptop. Replacing the PLC did not solve the problem, but replacing the chassis (which includes the power supply) did solve it.

Another time, all but one of the stations in their network switched the PLCs to program mode. I have no explanation for this, but I suspect some garbled command came through the radio network and caused it. They were all in TERM (remote) mode physically and the one site that stayed in RUN mode had a bad radio at that time so couldn't "hear" whatever noise it was that caused this.

I had to drive to all 11 sites and power cycle them before I could get them back into RUN mode with the PLC switch. I tried to connect to one of them with a laptop to see if I could retrieve some sort of error code, but the PLC would not connect until after it was power cycled and the ERROR LED was off the whole time. This was after I spent two hours jacking with the master radio and PLC, because when you lose all comms at once, it must be the master PLC or radio, right?

In your case, I would suspect electrical noise which might be alleviated with improved grounding or an AC line filter.

Welcome to the forum!

 

[Firejo]

Is the PLC controlling the pump through port 2? If so, maybe there is something about when the pump is running that is feeding current back through the port to the PLC causing it to “brown out” rather than a sharp black out.

I know that some PLC’s will do very strange things if you bring the power down slowly rather than abruptly. I had a small PLC (I think it was an older S7-200?) running a compressor on a fire department Air Unit (I didn’t build or spec the system). The 220VAC was supplied by a hydraulic generator and every once and a while (about 1 in 10 times) when you shut the generator down the PLC would dump or corrupt its memory. What we figured out was shutting the system down meant simply shutting off the hydraulics to the generator which would spool down rather than just shut off. During that “spooling down” period the voltage supplied to the PLC would drop slowly rather than all at once and the PLC didn’t like that.

(For anyone who is interested to know). The people who built the system wanted to fix it by updating the shutdown procedures to add turning the breaker off to the compressor before shutting down the generator (which we did). However, not everyone operating that rig was going to remember at 3:30 am to do that so I insisted on having them add a dropout breaker to the entire panel so if the power dropped below 210VAC (I thinks that’s where they set it) then the breaker would trip and the power to the panel would shut off abruptly. That fixed the problem without having to rely on someone who may have been up for 18 hours straight to remember to flip a switch before flipping another switch.

 

[bernie_carlton]

Do you have port configuration logic in the startup of the program? If not I can help you with that. First refer to this tech note:


https://support.automationdirect.com/docs/comportsetup/

 

[Jim3846]

I wonder if a constant voltage transformer would work here for the plc power and other similar sensitive devices.

google the use of CVT. Maybe that is the issue?

I have used these over the years and any noise problems have been mitigated by their use for power for sensitive components like plcs.