Trafag EXS 404/414 Ex Industat Thermostat

Explosion-protected capillary thermostat for process heating and cooling

The Trafag EXS 404/414 Industat is an explosion-protected industrial thermostat with a remote capillary sensor. It is marked II 2 G/D with Ex db eb IIC T6 Gb for gas and Ex tb IIIC T80 °C Db for dust, and Trafag lists ATEX and UKEX approval on the datasheet.

The sensor is a liquid-filled bulb and capillary that operates a microswitch, so the thermostat needs no power supply of its own. It has a floating change-over contact, and can be mounted in any position.

Technical specifications of the EXS 404/414

The switch point is temperature compensated with a bimetal lever, and options include locking the set point, fixing and sealing it at the factory, or presetting it to a customer value without a guarantee of switching accuracy. When ordering a preset, state the switch point and whether the contact should operate on a rising or falling temperature.

404 and 414 versions and standard types

The 404 has external adjustment of the set point and the 414 has internal adjustment. Ranges run from minus 30 to plus 40 degrees C up to plus 70 to plus 350 degrees C, with maximum sensor temperatures from 50 up to 380 degrees C depending on the range, and sensor diameters of 7 or 9 mm in stainless steel or copper.

Trafag lists two standard products with short lead time: the EXS230S for 20 to 230 degrees C with a 16 degree fixed differential, and the EXS350S for 70 to 350 degrees C with a 20 degree fixed differential, both with stainless steel 1.4435 sensors.

Selecting and installing the thermostat

Pick a range with the set point in the middle of the scale and a maximum sensor temperature above the worst-case process excursion. Order a protection tube or thermowell where the sensor must be removed without draining the line, and mount the housing where the ambient limit is respected.

The datasheet advises appropriate protection tubes or capillary protection in acetylene or similar critical media, and notes that nickel-plated copper sensors and brass capillary protection are being phased out. Follow the Trafag instructions for the cable gland, set point locking and sealing.

How the EXS 404/414 Ex thermostat works

The sensor bulb, capillary and bellows form a sealed system filled with liquid. As the temperature at the bulb rises, the liquid expands and moves the bellows, which acts against a spring and operates the microswitch at the set point. Because the measuring system is self-contained, the thermostat works without auxiliary power, and the remote bulb allows the switch housing to be placed where it is accessible while the sensor sits in the hot or cold zone.

Typical uses include high temperature trips on heaters and heat tracing, cooling water and lube oil temperature monitoring, freeze protection and simple temperature control of tanks and process lines in hazardous areas.

Selection and installation tips

Choose a range in which the required set point sits near the middle, and check that the maximum sensor temperature for that range is above any temperature the bulb can reach during upsets. Install the bulb in a thermowell where the process is pressurised or the medium is aggressive, and fully immerse the sensitive length so the reading is representative. Route the capillary without sharp bends, avoid kinks and support it along its length so it cannot be damaged by vibration or foot traffic. Choose external adjustment if operators need to change the set point, and internal adjustment where the setting should be protected.

In every hazardous-area installation the instrument is only one part of the protection concept. The certificate conditions, the cable and gland selection, the earthing and the documentation all have to agree with the area classification. Keep a copy of the certificate and the datasheet with the loop or equipment file, and record the tag number, type code and serial number at installation so that later inspections can trace each device back to its approval.

Supply in Oman and the GCC

Seven Star LLC supplies Trafag EXS 404/414 instruments across Oman and the GCC for oil and gas, petrochemical, utilities and marine projects. Send the full type code or the details listed below and our team can help confirm the correct ordering code before you request a quote. Where a project has several measuring points, list them together so that ranges, connections and certification can be checked against one another in a single review rather than one tag at a time.

Maintenance and periodic checks

Mechanical switches benefit from a simple routine. At each inspection interval, check the housing, cover seal and cable gland for damage or corrosion, confirm that the earthing connection is tight, and compare the switching point against a calibrated reference. Record the result alongside the original commissioning value so that any drift can be seen over time. If the switch point has moved or the housing shows damage, replace the unit rather than attempting repairs that could affect the explosion protection.

Documents and quotation

The Trafag datasheet for the EXS 404/414 (H72108z, 12/2025) is available from the link below. Browse our Temperature Instrumentation category for related products.

To request a quote, send the type, range, sensor material and diameter, capillary length and set point.