J
All:
The GE Versamax 2 amp relay output modules when driving even small inductive and non-inductive loads (such as relays and pilot lights) are susceptible to crosstalk between outputs. Model numbers affected are IC200MDL930A, IC200MDL940A, IC200MDD845A-C, IC200MDD846A, IC200MDD847A, IC200MDD849A, and IC200MDD850A.
Why bother everyone on the list with this? GEFanuc has not been supportive. To us, this is a potential safety issue that everyone using GE Versamax relay I/O should know about.
We found out a couple weeks ago that GEFanuc quietly redesigned all the relay output modules in May 2002 (all are now Rev B except IC200MDD845D), the revision improved noise immunity and suppression while driving inductive loads. The story we got was Rev A met their own internal specifications (whatever they were), but they decided to beef them up so the noise specs on the Versamax relay module would meet the noise specs on their 90-30 relay module.
We'd been occasionally bothered by several recently installed water and wastewater applications using the Versamax IC200MDD846A I/O module with what appeared to be faulty module relays. Sometimes it appeared the output would momentarily drop out, eventhough there was nothing in the PLC logic making it do so. We tried swapping output modules to see if a particular relay in the module was bad, but that didn't have any effect. We tried interposing relays, that didn't help either.
One of the relay modules drives a 30HP submersible wellpump with a softstart. When this relay output momentarily drops out, the softstart cycles the wellpump down then up again. It did this a number of times while the customer was watching. They had no choice but to run the well pump manually 'till we could get there.
After some investigation, we found that when the alarm pilot light was flashing each second, there was an occasional momentary (50-100ms) disconnect of all energized relays in not only the module driving the alarm pilot light, but in neighboring relay modules as well. The 50-100ms dropout disappeared when the alarm light stopped flashing.
Sloppy panel design? We designed it, which means it's probably perfect.
We've double-checked all the usual stuff - clean power to PLC, PLC power supply loading, snubbers on motor starters, output relay load current within specs, mains, AC control power, DC loop power all isolated, no obvious ground loops, etc.. We don't think we are abusing any part of the PLC I/O to the extent that would cause this type of problem.
Best regards,
Joseph P. Manns, PE (MN Reg#26762)
Arden Environmental Engineering Inc.
3550 Lexington Ave. N Suite 210
Shoreview, MN 55126
Ph 651-484-5415
Fax 651-484-5568
The GE Versamax 2 amp relay output modules when driving even small inductive and non-inductive loads (such as relays and pilot lights) are susceptible to crosstalk between outputs. Model numbers affected are IC200MDL930A, IC200MDL940A, IC200MDD845A-C, IC200MDD846A, IC200MDD847A, IC200MDD849A, and IC200MDD850A.
Why bother everyone on the list with this? GEFanuc has not been supportive. To us, this is a potential safety issue that everyone using GE Versamax relay I/O should know about.
We found out a couple weeks ago that GEFanuc quietly redesigned all the relay output modules in May 2002 (all are now Rev B except IC200MDD845D), the revision improved noise immunity and suppression while driving inductive loads. The story we got was Rev A met their own internal specifications (whatever they were), but they decided to beef them up so the noise specs on the Versamax relay module would meet the noise specs on their 90-30 relay module.
We'd been occasionally bothered by several recently installed water and wastewater applications using the Versamax IC200MDD846A I/O module with what appeared to be faulty module relays. Sometimes it appeared the output would momentarily drop out, eventhough there was nothing in the PLC logic making it do so. We tried swapping output modules to see if a particular relay in the module was bad, but that didn't have any effect. We tried interposing relays, that didn't help either.
One of the relay modules drives a 30HP submersible wellpump with a softstart. When this relay output momentarily drops out, the softstart cycles the wellpump down then up again. It did this a number of times while the customer was watching. They had no choice but to run the well pump manually 'till we could get there.
After some investigation, we found that when the alarm pilot light was flashing each second, there was an occasional momentary (50-100ms) disconnect of all energized relays in not only the module driving the alarm pilot light, but in neighboring relay modules as well. The 50-100ms dropout disappeared when the alarm light stopped flashing.
Sloppy panel design? We designed it, which means it's probably perfect.
We've double-checked all the usual stuff - clean power to PLC, PLC power supply loading, snubbers on motor starters, output relay load current within specs, mains, AC control power, DC loop power all isolated, no obvious ground loops, etc.. We don't think we are abusing any part of the PLC I/O to the extent that would cause this type of problem. Best regards,
Joseph P. Manns, PE (MN Reg#26762)
Arden Environmental Engineering Inc.
3550 Lexington Ave. N Suite 210
Shoreview, MN 55126
Ph 651-484-5415
Fax 651-484-5568
