The INTERTEC-Hess TC D is an explosion-proof digital PID heating controller purpose-built for temperature regulation of equipment and air inside protective enclosures, cabinets, and heat trace lines in hazardous locations. Designed to operate as part of Intertec's CPxxxTHERM HI explosion-proof heater systems, it carries ATEX, IECEx, and CSA certifications for Zone 1 & 2 (gas) and Zone 21 & 22 (dust) deployment. A fully encapsulated, all-solid-state construction with no mechanical switching contacts ensures reliable long-term operation in corrosive, high-humidity, and marine environments—from Arctic cold to Middle Eastern heat.

ATEX/IECEx Hazardous Area Deployment

• Ex e mb IIC T4 (Gas): The combination of increased safety (Ex e) terminals in a separate, freely accessible compartment and silicone-encapsulated electronics (Ex mb) provides maximum explosion protection with maintainability. IIC gas group covers all industrial gases and vapours, including hydrogen and acetylene, classified for use in Zone 1 and Zone 2.
• Ex tD A21 IP66 T130 °C (Dust): Certified for Zones 21 and 22—combustible dust atmospheres such as grain milling, coal handling, and pharmaceutical powder processing facilities. The IP66-rated aluminium enclosure prevents dust ingress and withstands strong water jets during washdowns.
• International Certifications: PTB 04 ATEX 2022 X, IECEx, CSA C/US, and GOST compliances simplify global specification and eliminate the need for separate regional certifications on international projects.

Solid-State Triac Power Switching & PID Control

• Zero-Cross Triac Output: Integrated Triac switching element with zero-voltage crossover technology virtually eliminates radio frequency interference (RFI) and power losses associated with relay-type control. Output is fully proportional—no staircase switching, no temperature oscillation.
• PID/PD Algorithm: High-precision proportional-integral-derivative control maintains tight setpoint accuracy from -50 °C to +80 °C ambient range. Group phase control further minimises power fluctuations, stabilising the electrical load on the supply line.
• Cold-Start Mode: Below -25 °C, the TC D automatically engages full-power output to heat its own PCB above -20 °C before resuming PID control—a critical feature for analyser cabinets and switches in unheated locations subject to extreme winter conditions.

Redundant Safety with Three Sensor Inputs

• KTY External Sensor (Intrinsically Safe): Mounted directly on the equipment or structure being temperature-controlled, the KTY silicon temperature sensor provides the primary feedback signal for PID regulation—with an Ex ia IIC rating that eliminates the need for an additional safety barrier.
• NTC Coil Limiter: A negative temperature coefficient thermistor embedded in the heater coil continuously monitors surface temperature at the heat source, electronically limiting heater output before the temperature class limit (T4 = 135 °C) is reached—a redundant protection layer beyond the primary PID loop.
• Internal Temperature Monitor: Monitors temperature inside the TC D's own aluminium enclosure, ensuring that the fully encapsulated electronics never exceed the rated 80 °C operating limit regardless of external conditions.
• Automatic Fault Shutdown: If any sensor detects an abnormal condition—excessive heater block temperature, sensor disconnection, or internal over-temperature—the controller immediately cuts power to the heater and signals a fault condition via the red LED indicator.

Modbus RTU Networking & PC Configuration

• Single-Network 31 Controllers: The RS-485 serial interface with standard Modbus RTU protocol allows up to 31 TC D units to be daisy-chained on a single bus segment, each with a configurable network address—perfect for multi-zone thermal management across large analyser houses and instrumentation clusters.
• Smart Heater PC Software: Intertec's complimentary configuration tool provides graphical temperature trending, data logging, and programming of PID constants (P & I terms), user-defined temperature ramp profiles, and heater temperature limits—all without opening the Ex e terminal compartment.
• LabView VI Drivers: Complete LabView virtual instrument drivers enable direct integration into automated test systems, quality assurance benches, and engineering development platforms.
• Setpoint Adjustment Without PC: Basic temperature setpoint changes can be accomplished directly using the side-mounted buttons without connecting a computer, verified by the two-colour green/red status LED.

Mounting, Dimensions & Technical Data

• Physical Dimensions: 57 × 125 × 80 mm (W × H × D)—compact enough to fit inside cable termination boxes or on the side of a GRP enclosure.
• Cable Entries: 2 × M20 cable glands standard (optional 3rd M20 knockout for separate industrial bus cable). All terminals are Ex e accessible in a separate compartment from the fully encapsulated electronics.
• Housing Material: Seawater-resistant anodised aluminium with black powder coating—validated for offshore platforms, coastal petrochemical sites, and marine applications.
• Current Derating Table (230 V AC): 40 °C: 10 A (2300 W) | 50 °C: 8.7 A (2000 W) | 65 °C: 6.5 A (1500 W) | 80 °C: 4.4 A (1000 W). Minimum load 250 mA. For ambient temperatures above 80 °C, the controller must be mounted outside the heated area with the external sensor deployed to the measurement point.