Is DeviceNet sensitive to cold?

I'm running a distribution terminal on ControlLogix 5580. It's been stone cold where we are and we haven't run some of this equipment since being hit by the deep freeze. The PLC and MCC are housed in a converted Conex box that has a heater, but it hasn't been functioning for several years.

Today out of no where we had 2 Devicenet failures, one on a large motor run off an AB SMC, the other a simple motor. The guys were able to clear the faults by rebooting them, and they would both start but reported higher than normal startup current. The current on the small motor came down to a normal level then would trip, the larger reported VERY high startup current and shut down almost immediately.

We couldn't find any problems with either of these, but the guys put a small space heater in the Conex so he could thaw himself out from time to time. We never did find an issue, but it started working normally again just a little while ago.

The only thing I can think of is that the room itself was warmer now, it got up to about 60 degrees in there. Is it likely that this was the source of the problem?

Jcooli09 said:

I'm running a distribution terminal on ControlLogix 5580. It's been stone cold where we are and we haven't run some of this equipment since being hit by the deep freeze. The PLC and MCC are housed in a converted Conex box that has a heater, but it hasn't been functioning for several years.

Today out of no where we had 2 Devicenet failures, one on a large motor run off an AB SMC, the other a simple motor. The guys were able to clear the faults by rebooting them, and they would both start but reported higher than normal startup current. The current on the small motor came down to a normal level then would trip, the larger reported VERY high startup current and shut down almost immediately.

We couldn't find any problems with either of these, but the guys put a small space heater in the Conex so he could thaw himself out from time to time. We never did find an issue, but it started working normally again just a little while ago.

The only thing I can think of is that the room itself was warmer now, it got up to about 60 degrees in there. Is it likely that this was the source of the problem?

Click to expand...

Our devicenet scanners have never had an issue (1756-DNB)

Devicenet cards on each drive, or overload, etc have temperature specs on them in the manuals. Some are -20C - 40C, some are -40C - 60C.

If you go colder, the temperature compensation on the sense resistors could wander a bit? The hall effect sensors on the large motor could give bad readings .. maybe.

The devicenet communications part seems to be working though.

We keep our devicenet stuff inside our MCC rooms, so I have not experienced that one as yet (And hope that I don't)

I've seen extreme cold shut down numerous electronic devices. PLC IO, soft start drives, variable frequency drives, for example.

If it were me, I'd be looking at the motors/gearboxes. Random D-Net faults are one thing, but motors tripping on over current in very cold weather makes me think of oil that is too cold.

Bubba.

I think willxfmr is spot on. The big clue here is the increased current on start up when it's cold. Any motor that is connected to something that driving liquid (a pump, gearbox with lubricant, etc…) is going to have to work harder the colder it gets. As fluids get colder, they get “thicker” and harder to move. If it is a gearbox it should have temp ratings hopefully indicating the power required to drive it at what temp (maybe I’m dreaming here). If it continues to be a problem in cold weather you might look to see if it has the correct lubricant for cold weather exposure.

Quite cold here at the moment too...

Quick comment as I'm of home now...

This morning 2 out of our 3 Air Compressors for the plant failed to start (duty - 2 in use 1 in standby). One threw repeated errors either "VSD Fault 7" or "23". These are "Check Encoder" and "Check Motor Underspeed" respectively.

On the other one, a slightly different model, we were getting "2nd Stage Temp Fault". These are large Ingersoll Rand Compressors and they have quite verbose data available from the many feedbacks including temperatures. When we scrolled through the Status menu all the temps were quite low (3-4 deg.). It was freezing cold out in the Service Block this morning. We rang the Service Company and they said yeah, the motors are too cold. We fetched a couple of extension leads and small 2KW blow heaters from the offices. We left them inside the Compressors for a couple of hours before they would eventually start up without error and they've stayed running since. We've had colder mornings here before and yet this had never happened. Maybe it had gotten down very cold over night while they were off.

So yeah, cold motors/gearboxes/lubricant, it's definitely a thing.

Regards,
George

Usually with coldness comes dampness, and that could potentially interfere with DeviceNet signals, or even Power.

Most likely the signals could get deteriorated because the dampness would be seen as parallel resistance (i.e. in parallel with the end terminating resistors).

I don't think it would do any harm to coat any exposed terminations, or even inside plugs & sockets, with a moisture repellent spray, such as WD-40 perhaps ?


EDIT : I have found this product which claims to do exactly what it says on the tin, a bit pricey though....

Jcooli09 said:

The PLC and MCC are housed in a converted Conex box that has a heater, but it hasn't been functioning for several years.


We couldn't find any problems with either of these, but the guys put a small space heater in the Conex so he could thaw himself out from time to time. We never did find an issue, but it started working normally again just a little while ago.

Click to expand...

Based on this - it sounds like you had a heater that wasn't working. After they put a space heater in, it started working.

Check the temperature rating on any electrical components you are using. It is fairly standard to see -10 deg C to 55 deg C (14 deg F to 131 deg F) which would require the heating listed above.