CompactLogix L33ER loosing program

Hi, I have a customer that we did an upgrade for about 6 months ago, replaced a SLC503 w/ 5 IA16 and 5 OX8 IO cards, with a CompactLogix L33ER w/ 5 IA16 and 5 OW8I IO cards. 120vac power supply (1769-PA4). SLC503 was in service for many years with minimal issues.

About 4 months after being in service without any problems, on 2 separate occasions the program was wiped from the processor and loaded from the SD card. 3rd time the processor was dead (solid red OK indicator).

Replaced the PLC, 2 weeks later, again something happens and the PLC lost its program, loaded from the SD card. At this point we are trying to figure out what could be happening. Customer has an entire building surge protector, PLC is fed from a APC UPS. We decided to try powering the PLC via 24vdc using a 1769-PB4 and a new phoenix contact quint power supply, fed from the APC UPS, thinking this would provide some isolation. Checked for proper grounding and shielded all ethernet cables. Couple days after making these changes, same thing happens again.

I upgraded the firmware from version 24 to 30. Thinking maybe an input could be causing this I started tracing out wires and found 120vac inputs coming from multiple sources, some from within the same control panel as the PLC, others from outside the control panel. For instance there are 9 different breakers coming from a 120/240v breaker panel that feeds power into this panel. 1 of those provides the 120vac control power for this panel, this is where most of the inputs get their power from.

I am really at a loss for what is causing the processor to loose the program. My next thought is a surge coming in on one of the inputs, but all of the inputs still function.

The older CompactLogix such as L32E and L35E era were notorious for losing the program during a spike.
I'd suggest an inline filter for the 120VAC feeding the power supply.
It worked with the older ones like a charm!!
Personally, I do not think it is the Input spikes (if any) that wipe the program.

If it is still connected using the pb4 you could replace the power supply with a 24v power supply/ups to get rid of the possible larger system spikes. Also where on the bus is the power supply in relation to the cpu? It is only allowed max 3 slices away from each other if it’s more than that it could be a problem too.

cdrum543 said:

....Customer has an entire building surge protector, PLC is fed from a APC UPS. We decided to try powering the PLC via 24vdc using a 1769-PB4 and a new phoenix contact quint power supply, fed from the APC UPS, thinking this would provide some isolation. Checked for proper grounding and shielded all ethernet cables. Couple days after making these changes, same thing happens again.

Click to expand...

Sounds like you are doing everything I would, I would also run another ground rod right next to the cabinet and connect it to the system ground

AND, not trying to sound like a smart *** but I would pull the PLC and install another PLC for "5 IA16 and 5 OW8I" can you use a 1400? or another brand, anything to stop the bleeding of a 3,000 dollar CPU every time, that can add up fast, not counting the downtime.

We had the same problem. We noticed that the NEMA 4 box had a new conduit added on top just above the controller. It turned out that someone drilled a hole and allowed the shavings to fall into the backplane. Everything worked except for the program memory loss when powered down. We shook the shavings out like pepper and billed the contractor who installed the conduit delivering the network cable for time lost.

Thanks for the replies!

jholm90 said:

If it is still connected using the pb4 you could replace the power supply with a 24v power supply/ups to get rid of the possible larger system spikes. Also where on the bus is the power supply in relation to the cpu? It is only allowed max 3 slices away from each other if it’s more than that it could be a problem too.

Click to expand...

There are 3 IO modules to the left of the power supply and 7 to the right.

It is still connected using the PB4 24vdc power supply. The 24vdc Phoenix contact power supply is fed from a APC UPS. I was thinking about a filter for the 120 supplying the power supply.



We also found out that the power feed into the plant is a 3 phase open delta configuration.

cdrum543 said:

Thanks for the replies!



There are 3 IO modules to the left of the power supply and 7 to the right.

It is still connected using the PB4 24vdc power supply. The 24vdc Phoenix contact power supply is fed from a APC UPS. I was thinking about a filter for the 120 supplying the power supply.



We also found out that the power feed into the plant is a 3 phase open delta configuration.

Click to expand...

Take a look at this for feeding power to the PLC bus power supply as it will give you a buffer time for any ac noise problems.

https://www.phoenixcontact.com/onli...k=P-22-07-07-01-01&tab=1&selectedCategory=ALL