Spare ML1400

Tom@Pton · Apr 17, 2015

One of my customers wants a spare to his ML1400. Is there a trick I need to know about programming this spare? It will not have any of the other I/O installed until after it is in place. If and when it is ever needed.

When I downloaded the file it immediately, or soon after, faulted.

Ken Roach · Apr 17, 2015

In general, MicroLogix and SLC-500 controllers will immediately fault when commanded to do into RUN mode if you don't have the I/O modules that are defined in the user program actually connected to the controller.

This is on purpose; if the controller doesn't have the input or output devices the control program needs, it's not going to try to run a user program or control outputs. It has no way of knowing if the missing I/O are important or unimportant.

SLCs let you inhibit I/O modules and go into RUN mode with missing ones, but I've never tried to do so with MicroLogix 1400.

Tom@Pton · Apr 17, 2015

Ken Roach said:
In general, MicroLogix and SLC-500 controllers will immediately fault when commanded to do into RUN mode if you don't have the I/O modules that are defined in the user program actually connected to the controller.

This is on purpose; if the controller doesn't have the input or output devices the control program needs, it's not going to try to run a user program or control outputs. It has no way of knowing if the missing I/O are important or unimportant.

SLCs let you inhibit I/O modules and go into RUN mode with missing ones, but I've never tried to do so with MicroLogix 1400.

I suspected I should have left it in the program mode.

OkiePC · Apr 17, 2015

If you leave it in program mode, it will still be in program mode next time you apply power. Putting it in run mode means that it will try to go to run mode next time power is applied. With the right I/O modules, I think that is what you want.

gbradley · Apr 17, 2015

I would buy and install the 1762 cards that you need, so that it is setup the same as your field unit.
Then, hopefully it will not fault.
Good Luck!

Firejo · Apr 17, 2015

I’m guessing the reason for having a spare PLC is so that if it fails there will be very little down time. With that, what if one of the I/O modules fails? If they want spares, they should have spares of everything (within reason) that might fail and cause a delay in the system running.

Tom@Pton · Apr 19, 2015

Firejo said:
I’m guessing the reason for having a spare PLC is so that if it fails there will be very little down time. With that, what if one of the I/O modules fails? If they want spares, they should have spares of everything (within reason) that might fail and cause a delay in the system running.

Yes, no doubt the best plan.

Thanks again to all.

Spare ML1400

Tom@Pton

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Ken Roach

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