Latch only what must be remembered
An OTE output turns off as soon as its conditions are gone. An OTL output stays on until another rung clears it.
Why
- With OTE, every reason to stop is in one rung you can read. With OTL, the reasons are spread over the OTU rungs.
- A missed OTU leaves a motor or valve on. A missed seal condition just stops it.
- Alarms and first-out faults should latch, so a short event is still seen. See Latch and reset.