The solid-state relay, heater circuit and temperature-controller output are part of the processing sequence, and their condition can contribute to a heater that stays cold, heats continuously, cycles erratically or warms more slowly than its peer zone.
Final limits, parts and adjustments remain configuration-specific; use the project-issued electrical drawing, heater data, controller manual and qualified electrical test instruction instead of applying a universal value.
Capture the first records at the line
Log heater zone, controller channel, SSR input and load terminals, protective device and heater nameplate. Mark when the concern appears during startup demand, steady-state cycling, alarm behavior and output-off state. Include the operator observation, line state, stock or job identity and the last known acceptable processing period. This prevents several different faults from being grouped under one general alarm or quality description.
Read command and load records together
| Observed behavior | Records to collect | Diagnostic direction |
|---|---|---|
| Controller requests heat but zone remains cold | Output indicator, SSR input, load voltage and measured current | Control path, open load or protective device |
| Zone heats with command off | Time-aligned controller command, qualified load-current evidence and clearly identified voltage test points | Separate continued heater power from thermal lag; investigate the actual switching path |
| Temperature oscillates widely | Trend of setpoint, process value, output and line cycle | Sensor contact, tuning, load switching or airflow |
| SSR heat sink is discolored | Cabinet temperature, mounting behavior and terminal inspection | Cooling loss, loose connection or overload |
| Fuse opens repeatedly | Heater resistance, insulation test by qualified staff and circuit identity | Ground fault, short circuit or incorrect protection |
The diagnostic directions are possibilities to investigate, not confirmed causes. Compare observations with the actual circuit, tooling and component documentation before replacing a part or changing a setting.
Control hazardous energy and preserve references
Apply the site lockout and isolation instruction for electrical, pneumatic, vacuum, thermal, gravity and stored mechanical energy that applies to this equipment. Verify the zero-energy state before guards, terminals, tubing, tooling or drive components are accessed. Hot surfaces and charged electrical parts may remain hazardous after the line stops.
Photograph connectors, tube routing, witness marks, adjustment positions, wiring labels and device orientation before disassembly. Qualified personnel should perform live electrical or pressure measurements only when the specified diagnostic instruction specifically requires them and appropriate controls are in place.
Inspect the device in its complete load path
Follow the complete zone from sensor contact to controller output, SSR input, protective device, heater and return conductor. An illuminated SSR indicator does not prove that load current is flowing, and a hot zone does not prove correct sensing. An OFF command is not electrical isolation. SSRs can have off-state leakage current; a voltage reading must identify whether it is across the SSR output terminals, across the heater or relative to another reference. Do not diagnose a shorted SSR from an unspecified voltage reading alone. Qualified personnel must interpret command, actual load current and temperature history using the installed circuit and an approved procedure.
Compare the affected component with the related electrical terminal heating inspection guide before deciding that one observation identifies the cause.
Verify the repair in stages
Before power or pressure is restored, confirm tools are removed, connections are secure, guards are reinstated and the work area is clear. Use the documented heating-zone recovery procedure first. A jog or slow-cycle movement is not a substitute for checking heater switching and protective functions. Progress to controlled production only after the required electrical and thermal checks.
After an authorized repair, trend process value and switching command through warm-up and stable processing, confirm current is consistent with the documented load, and inspect the first formed cups. Do not release the line based only on one acceptable cycle. Document the parts or configuration values changed, final observations, retained samples and the person authorized to return the equipment to processing.
Component reference
Omron SSR technical guidance describes off-state leakage in its SSR circuits. This explains why command and electrical state must be distinguished; it does not identify the brand installed on a HANNAI machine.
Can an SSR fail in the on state?
Yes. Some failure modes leave the load energized, so isolation and verified electrical testing are essential.
Is the controller output lamp enough to diagnose the circuit?
No. It indicates a command state, not verified voltage, current, heater continuity or heat transfer.
Can any SSR with the same current label be substituted?
No. Control type, load type, voltage, thermal design, protection and approval must match the documented circuit.
Who should open the live control cabinet?
Only qualified personnel following the site electrical-safety instruction and the line documentation.
Send the line model, device identity, labeled samples, sequence video, checks and service history through our inquiry page. HANNAI can review the records against the project-issued line configuration.