ATEX heating solutions — from design to operation
Selecting a product with an Ex marking is the starting point — not the finish line.
Most ATEX heating failures are not caused by the heating element itself — but by incorrect system design, control architecture or installation.
An ATEX heating system is not a standard heating system with a different label. The zone classification imposes direct constraints on element surface temperature, control redundancy and the certification status of every electrical component within the zone boundary. Meeting those constraints starts with understanding the process requirements and working through the classification parameters systematically — not by selecting from a catalogue and checking the ATEX box at the end.
The result of a correctly designed ATEX heating system is a unit that delivers the required process temperature reliably, within the T-class limit under all operating conditions, with a control architecture that fails safely, and with documentation that supports a compliant installation.
ATEX-rated heating product types
The same product categories used in unclassified environments are available in ATEX-rated versions — with differences in element construction, watt density, control architecture and available configurations.
- Drum heaters (band and jacket). Band heaters wrap the outside of a 200-litre drum; jacket heaters enclose a larger section of the drum wall. In ATEX versions, element watt density is reduced relative to standard equivalents to maintain T-class compliance at the element surface. Zone 1 (Category 2) versions are available in a narrower range of standard configurations than Zone 2 equivalents. Custom power levels and drum dimensions for Zone 1 require Notified Body involvement in the certification.
- IBC heaters. Blanket-style heaters that wrap around intermediate bulk containers (typically 1000 litres). Similar T-class constraints to drum heaters, with the added consideration that the larger surface area and lower watt density of an IBC heater typically gives more margin on T-class than an equivalent drum band heater.
- Immersion heaters. Flange-mounted or screw-in elements that heat the medium directly from inside the vessel. T-class compliance in immersion heaters is highly dependent on ensuring adequate medium contact is maintained — a partially exposed element in a low-fill vessel can exceed T-class limits at full power. Dry-run protection is an integral part of ATEX immersion heater design.
- Trace heating cables. Self-limiting or constant-wattage trace heating cables for pipe freeze protection, viscosity maintenance and process temperature maintenance in classified areas. Self-limiting cables are inherently more manageable from a T-class perspective — their output decreases as temperature rises. Constant-wattage cables require more careful T-class verification against worst-case conditions.
- Heated hose assemblies. Flexible hoses with integral heating element for transfer of viscous or temperature-sensitive media. ATEX-rated heated hoses are used where the transfer line passes through or is located within a classified zone. The heating element, connections and control components must all carry appropriate certification.
- Custom and bespoke systems. Non-standard vessels, unusual geometries, very high watt requirements with tight T-class constraints, or integrated heating and transfer systems. Designed from scratch against the zone classification, substance data and process requirements of the specific installation.
The design process for an ATEX heating system
A correctly sequenced design process resolves the classification parameters before any product is selected. In practice, the inputs required are:
- Zone classification drawing. Defines zone boundaries, required equipment categories and the substances present. Equipment selection follows the drawing — not the other way around.
- Substance data. The auto-ignition temperatures and gas groups of all substances that may be present in the zone. The most restrictive substance governs T-class and gas group selection.
- Process requirements. Required medium temperature, volume, vessel type and geometry, ambient conditions, duty cycle. These determine the heating power needed and the element geometry required to deliver that power within the T-class constraint.
- Control architecture. Primary setpoint controller and independent safety cut-out, both located relative to zone boundaries. Manual-reset cut-out type required. Intrinsically safe sensor circuits where sensors are in the zone.
With those inputs confirmed, the element geometry can be calculated: total surface area required to deliver the heating power at a watt density that keeps the element surface below the T-class limit under worst-case conditions. This calculation is specific to the installation — it cannot be substituted by selecting a standard product rated to the correct T-class without verifying that the standard product's element geometry matches the watt density requirements of the actual installation.
The certification route is determined in parallel: Category 3 (Zone 2) systems can be certified by the manufacturer through the Declaration of Conformity route. Category 2 (Zone 1) systems — particularly custom configurations — require Notified Body involvement, which must be planned into the project schedule from the outset.
We design ATEX heating systems based on your zone classification, substance data and process requirements — not by adapting standard catalogue products.
Control architecture requirements
ATEX heating installations require two independent temperature-limiting devices in series — not a single controller with a high-temperature alarm. The secondary device must be a manual-reset type: once it trips, heating cannot resume without deliberate human intervention.
The primary device maintains the operating setpoint. A PID controller is standard. The secondary cut-out is set above the operating setpoint but below the T-class surface limit. Its purpose is to ensure that a temperature exceedance is investigated before the system returns to service — not silently self-corrected.
Both devices must be located and certified appropriately for their position relative to the zone boundary. If located within the classified zone, they must carry ATEX certification for that zone. If located outside the zone — the preferred arrangement in most installations — no ATEX rating is required for the controller or cut-out enclosures themselves. The sensor cables running into the zone do require intrinsically safe circuit treatment: Ex ia circuits with certified safety barriers or galvanic isolators on the safe-area side of the zone boundary.
The fail-safe condition must be verified: if the primary controller fails in the call-for-heat state, the element will receive sustained full power. The element design must ensure that the surface temperature under this condition cannot reach the T-class limit. This is checked as part of the element design, not assumed.
Installation, commissioning and documentation
An ATEX heating system leaves the manufacturer with the equipment certification in order. Compliance of the installation depends on what happens next.
Installation must follow IEC 60079-14 — the standard for electrical installations in explosive atmospheres. This governs cable routing, zone boundary crossings, cable gland specifications, enclosure entry requirements, bonding and earthing, and documentation. Every deviation from the zone drawing must be assessed before installation proceeds.
Cable glands are a consistent failure point. An Ex d enclosure fitted with a standard unrated cable gland is no longer Ex d compliant regardless of the enclosure's certification. Glands must be certified for the protection concept of the enclosure they serve, and must be correctly torqued. This applies to every zone boundary entry in the installation — power cables, sensor cables and any other penetration.
On commissioning, the safety cut-out setpoint must be verified against actual operating conditions, not only against the nominal setpoint. The manual-reset function must be tested. The intrinsically safe circuit segregation must be physically confirmed. These checks form part of the initial inspection record required under IEC 60079-14 and must be retained as part of the installation documentation.
Related resources
ATEX heating systems designed and built in-house
HeatXperts designs and manufactures ATEX-certified heating elements and integrated heating systems for Zone 1 and Zone 2 environments. Element geometry, watt density, control architecture and certification route are determined at the design stage, based on the zone classification, substance data and process requirements of each installation.
Every system is delivered with the certification documentation the installation requires — including component certificates, declarations of conformity and system-level documentation referenced to the site zone drawing.