Temperature Switches & Thermostats – safe switching, reliable control

FAQ on Temperature Switches & Thermostats

Answers on types, hysteresis, accuracy, mounting, IP/Ex, outputs, loads and digitalization.

What are temperature switches & thermostats particularly suitable for?

For safe on/off control when limits are exceeded or undershot (e.g., fan, heating, cooling, alarm) without complex control loops.

What’s the difference between a thermostat and an electronic temperature switch?

Thermostat: mechanical/capillary, mains-independent, direct switching. Electronic switch: sensor + electronics, more precise setpoints, display/diagnostics, digital interfaces.

What types are available?

Which outputs are available?

What is hysteresis and why is it important?

Hysteresis is the difference between switch-on and switch-off points. It prevents chattering and protects actuators. Often fixed in mechanical devices; freely adjustable in electronic ones.

How accurate is the switching?

Mechanical typically ±1…3 K, electronic typically ±0.2…0.5 K (depends on sensor, installation and ambient conditions).

What about repeatability/drift?

Mechanics: higher drift over lifetime. Electronics: very good repeatability, drift can be compensated via calibration.

What switching loads are possible?

Relays depending on type e.g. 250 VAC up to several amperes; solid-state for frequent switching. Protect inductive loads with snubbers.

How do I select the temperature range?

Choose a range so that setpoint + hysteresis stay within permitted sensor/enclosure temperatures; include safety margin for ambient influences.

What IP ratings are available?

Depending on design IP54–IP69K. For wash-down use hygienic sealing and cable glands with strain relief.

How is mounting done (pipe/medium/air)?

• Pipe/surface: pipe clamp + thermal paste
• Immersion sleeve: for pressurized media (316L, etc.)
• Air/duct: ensure airflow, use shielding

Which immersion sleeve/thermowell is suitable?

Consider material (e.g., 316L), pressure/temperature, flow, and length (short time constant); enables replacement without draining the medium.

How do I set the switching point?

Mechanical: via scale/screw. Electronic: via keys/display, PC/IO-Link. Document parameters for QA/traceability.

Which sensing principles do electronic switches use?

Typically RTD (Pt100/Pt1000) or thermocouple—internally linearized; choose based on range, accuracy, response time.

How fast do thermostats/switches respond?

Mechanical: depends on installation/thermowell (seconds). Electronic: short response times, configurable filters/averaging.

How do I ensure EMC-compliant installation?

Shielded, twisted cables, proper grounding, separation of power/signal lines, optionally line filters/ferrites. Ensure equipotential bonding.

Use in hazardous (Ex) areas (ATEX/IECEx)?

Possible with Ex i or Ex d versions. Observe zone, temperature class, marking and suitable barriers/connectors.

SIL/functional safety—possible?

Some electronic devices are available with SIL data. Consider proof-test intervals, diagnostic coverage and NE43/NE107.

How do I test/calibrate switching points?

Using a temperature calibrator/bath and reference sensor. Verify setpoint on rising/falling temperature, document hysteresis; intervals typically annually.

How do I integrate the devices into PLC/IIoT?

Binary inputs (relay/PNP/NPN) for alarms; analog value + limit via 4–20 mA/0–10 V; IO-Link/Modbus for parameters/diagnostics → edge/gateway → MQTT/HTTPS.

Typical failure modes and remedies?

• Contact wear → size relay correctly, RC/varistor protection
• Chattering → increase hysteresis, decouple the control path
• Offset/drift → calibrate, check installation
• Interference → EMC measures, optimize cable routing

Do you support selection & commissioning?

Yes. We size sensor/thermowell, define setpoints/hysteresis, select outputs, handle parameterization and supply calibration certificates.