Service Report: Old PLC Retrofit

We were asked by Cornell University to look at replacing the VFD  and programmable logic controller (PLC) for their boiler’s induced draft (ID) fan.  The PLC was an old Telemechanique unit, and the program resided on a 5.25 inch floppy. 

To begin the process  we had to figure out their program.  Whomever had done the original program was long gone, and factory support on a unit that old wasn’t an option.  We first found and purchased an old DOS PC with a 5.25 inch floppy port.  Using DOS 3.0 (remember that?) we  began looking at the original program.  Following a number of work-arounds we were finally able to see the ladder logic, of which the rungs, by the way, were unlabeled by the original programmer.

Following that, it took a few days of tracing and deciphering to completely understand and upgrade  the old code to something more modern.  We were then able to program a more standard AB PLC.  The original drive was replaced with a modern Yaskawa E7.

The folks at Cornell were pleased enough with the results to proudly point it out to some other university folks visiting their facilities area.

At EMA,  we strive to provide solutions and service, not just equipment and promises.  EVEN if it means rounding up an old DOS PC to decipher the problem.  We think our customers deserve nothing less.

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