I need to increment a number greater than 32676 i a SLC 500 PLC for an air compressor run time. currently a run status input increments a RTO timer and resets at 3600 seconds. the RTO done bit increments a CTU instruction every hour with a preset of 32676. The accum is moved into n10 to display on HMI. The problem is the air compressor run time is now at 33000 plus hours. What is the best way to fix this problem?

 

If the number is just used for display, the easiest solution would be to cascade the counter into another counter and put the two display fields side by side on the screen so they look as much like one number as possible.

If the preset for the first counter is set to 999 the overall effect will still be that of a decimal display. If you end up with a small gap between the position on the screen of the two numbers (due to HMI limitations), you can call that gap a visual thousands separator (that is why you would use 999 instead of 9999).

If the preset for the first counter is set to 999, it will cascade into the second counter every 1000 hours. The two counters together would give you 32767 * 1000 = 32767000 hours, or 3740 years. That is probably somewhat beyond the expected life of the machine.