The soak that never really happened

What the checks test

1. T1Heat with a remembered band, then soak for five uninterrupted seconds.
2. T2Cool through a separate circuit; never command heating and cooling together.
3. T3Low water and high temperature win immediately; Reset cannot restart the process.

The checks run 9 tests on the machine, scan by scan: Heat, continuous five-second soak, cool and latch completion; Cold interruption must restart the whole soak; Hot interruption is not a valid soak; Hysteresis remembers both directions inside the band; Low water inhibits phase 10; Low water inhibits phase 20; Low water inhibits phase 30; High temperature trips; Reset while hot is refused; Permission and Stop cannot create an automatic restart.

Where you’d find this

A food factory heats a batch, keeps it hot for a set time, then cools it before it goes out.

If the hold timer counts while the batch is too cold, the batch is not properly treated. Heating and cooling at once wastes energy and hides a mistake in the code.

How it should behave

States and entry

0 idle; 10 heat; 20 soak; 30 cool; 50 complete; 90 trip. A fresh Start enters 10 only with Permit, no Fault, Level >= 10 L and Temperature < 40°C. Only one phase transition per scan. State is checked exactly; ordinary phase commands may follow the previous or new state for one scan.

Heating band

NeedHeat turns TRUE at Temperature <= 31.5°C and FALSE at >= 32°C; between those values preserve it. HeaterOn follows that memory only in 10/20. MixerOn is ON in 10/20/30. In 10, Temperature >= 32°C enters 20. Never command HeaterOn and CoolValve together.

Continuous soak

Delay times only in 20 with Temperature from 31.5 to 32.5°C inclusive. The first enabled invocation starts at zero. Five uninterrupted seconds enters 30. Outside that band, return to 10 and reset the entire wait; a later recovery needs five fresh seconds.

Cooling and completion

CoolValve is ON only in 30, HeaterOn OFF. Temperature <= 24°C enters 50: HeaterOn/CoolValve/MixerOn OFF and Done ON. Completion latches until a valid Reset. CoolingFlow and CoolingPower show the separate utility circuit; coolant does not change Level.

Immediate priority

In 10/20/30, lost Permit, Fault, Level < 10 L or Temperature >= 70°C immediately enters 90, Alarm ON and all process commands/Done OFF. Stop returns to idle unless tripped. Reset in 50/90 needs Start released, Permit, no Fault, Level >= 10 L and Temperature < 40°C. Ignore Reset during an active phase. A held Start never restarts after Stop or trip.

Watch the energy

HeatPower reports delivered heating; HeatingRate reports net °C/min. CoolOpen confirms actual valve travel. The 24 kW heater warms a larger water mass more slowly; the 12°C jacket removes heat according to temperature difference. Physical cut-outs are independent of your commands.

Run and briefly press Start. Watch delivered heating power and temperature rate. The 32°C soak takes five continuous simulated seconds; cooling then removes heat to 24°C. Use the Inputs tab to test a short temperature interruption.