An explosion-proof motor is the prime mover certified to run inside a hazardous area; a thermal relay is the protection element wired into its starter. They live in different enclosures, on different pages of the bill of materials, and answer different clauses of GB 3836 or IEC 60079 — but they are routinely confused in single-line diagrams and EOL quotations [S1][S6].
The confusion usually starts at the contactor panel. A process engineer asks for a "flameproof motor" and receives, instead, a cast-iron motor plus a small box bolted to the wall. Both are essential; only one carries the motor nameplate. Feice's 8060 series demonstrates the cleanest split: it packages the thermal element inside its own GRP enclosure so the relay can be paired with any flameproof explosion-proof motor the specifier has already approved [S1].
Definition and Scope: Two Products, Two Standards Routes
Explosion-proof motors are built to GB 3836.1 and GB 3836.2 in China, which mirror the IEC 60079-0 and IEC 60079-1 flameproof 'd' construction rules; TECO's AFBY/AFBU EVBY/EVFU lines carry the Ex d IIC T4 marking, with an Ex d II(H2) option for hydrogen service and IE3 efficiency compliance [S6]. NORD's hazardous-location portfolio covers the ATEX/IECEx side of the same scope, offering dust and gas protection in matched frame sizes [S5].
A thermal relay is a bimetallic or electronic overload device, not a motor. Feice 8060 is an "explosion- and corrosion-proof thermal relay," explicitly declared as not stand-alone — it must be installed inside or alongside an explosion-proof electrical enclosure to retain its certification [S1]. The relay's job is purely protective: it opens the contactor coil when winding current exceeds the set value, or when one phase drops out, saving the motor from a thermal fault that the motor's own flameproof enclosure cannot sense.
Selection Criteria: Match the Hazardous Area, the Gas Group, and the Motor FLC
Motor selection is dominated by gas group and temperature class. TECO's Ex d IIC T4 line covers the widest gas group in industrial use (IIC = hydrogen, acetylene, carbon disulphide) with a 135 °C surface limit, while the H2 suffix extends it to dedicated hydrogen atmospheres [S6]. NORD bundles the same Ex tb / Ex tc dust-zone protection in the same frame family, so a spec written for zone 1 gas + zone 21 dust can be satisfied by a single motor catalogue line [S5].
Thermal-relay selection is dominated by full-load current and trip class. Feice 8060 ships with an adjustable current-setting shaft on the enclosure face, plus main and auxiliary contacts for the contactor coil and a fault indicator — features that are mandatory for any overload device sitting ahead of a flameproof motor starter [S1]. The relay's hazardous-area marking is Class IIC, division 1 and 2, the same gas envelope as the motor, so a Class IIC thermal relay can be fronted with any Class IIC motor without re-classifying the panel.
Comparison: Motor vs Thermal Relay Across Four Decision Criteria
The two products differ on every axis a buyer cares about. The clearest pass: [S1]
• Function — Motor converts electrical to mechanical energy, certified to GB 3836.1/.2 / IEC 60079-1 'd' flameproof rules [S6]. Thermal relay opens the contactor coil on sustained over-current or phase loss; it carries no flameproof motor certification of its own and must be paired with a certified enclosure [S1].
• Hazardous-area marking — Motors carry Ex d IIC T4 (or higher gas group / lower T-class for special gases) [S6]. Feice 8060 relay carries the same IIC gas group and division 1 & 2 zoning, so panel builders can match them on gas group without a gap [S1].
• Installation location — Motor sits at the driven equipment; Feice relay is panel- or wall-mounted next to the contactor, in GRP (fibre-glass unsaturated polyester) housing for corrosion resistance [S1]. NORD's Ex motors ship in cast iron or aluminium depending on frame [S5].
• Cost driver — Motor cost scales with kW, frame, efficiency class (IE3 on the TECO line) and gas-group option (H2 adder) [S6]. Relay cost scales with current range, trip class, and enclosure material; Feice's GRP body trades cast-iron impact rating for chemical resistance, which is the right choice in seriously erosive gas atmospheres [S1].
Who Needs What: Splitting the Buy by Application
For a new hazardous-area pump or compressor skid, the spec must include both lines. TECO or NORD will supply the motor; Feice 8060 or an equivalent thermal relay will sit in the starter. Trying to specify "explosion-proof motor" alone and assuming overload protection is built in is a frequent error — TECO's catalogue shows the Ex d IIC T4 motor as a bare machine, with protection delegated to the panel builder [S6].
For a retrofit, the division is the same: the motor rarely changes, but the relay is often the device that fails first, and the new one must match the hazardous-area classification of the existing motor starter. Feice 8060's IIC + division 1 & 2 rating, plus adjustable current setting and phase-loss trip, makes it a drop-in for a stalled TECO or NORD motor panel where the original thermal element has been superseded [S1][S6].
For an OEM skid builder, the cleanest procurement is one motor line + one relay line, both IIC, both with the same dust/gas zoning. NORD's frame range covers dust-zone applications in the same family as gas-zone motors, so a single vendor can carry the explosion-proof motor on the BOM while the relay is sourced separately for the panel shop [S5].
Real Use Cases and Failure Modes
The Feice 8060 is positioned for "serious erosive gas environment" — chemical plants, offshore platforms with H2S exposure, and chlorine rooms. The GRP body, the phase-loss trip, and the IIC gas group are all pointed at the same operating envelope [S1]. The explicit warning that the device cannot be used alone is the most important line in the datasheet: install it outside an explosion-proof junction box or contactor enclosure, and the protection rating collapses.
On the motor side, the failure mode to design against is locked-rotor current. TECO's IE3 line runs to 1000 kW and higher in the Shanghai Electric portfolio, and a stalled rotor on a 1000 kW Ex d IIC T4 machine is the kind of event that will open a thermal relay within seconds — but only if the relay is set to the motor's actual FLC and the trip class matches the motor's thermal limit curve [S6]. Shanghai Electric's explosion-proof synchronous and asynchronous line covers the 10–1000 kW band where this protection logic matters most.
Limits, Constraints, and Sourcing Signals
Two constraints are common to both products. First, the hazardous-area marking on the motor and the relay must share the same gas group and zoning — pairing a Class IIC motor with a Class IIB relay downgrades the whole panel to IIB. Second, the enclosure material choice is a real trade-off: cast iron for the motor (impact resistance, heat conduction) and GRP for the relay (chemical resistance, light weight) [S1][S5][S6].
Trackable signals for the next planning cycle: the Shanghai supplier base on Made-in-China lists more than 20 active explosion-proof-motor vendors serving the 10–1000 kW band as of 2026-06, which keeps lead times for TECO-class machines inside 8–12 weeks for standard IE3 frames. Feice continues to publish the 8060 as a stock SKU with adjustable current range and GRP enclosure, signalling it remains an active line for 2026 hazardous-area panel builds [S1]. For buyers tracking relay-vs-motor allocation, the cleanest check is to confirm the relay's gas group, division rating, and trip class against the motor's GB 3836.1/.2 certificate before release. Related reading on adjacent protection gear is mapped in this portable gas detector total-cost breakdown, and the panel-side sealing question is covered in the explosion-proof junction box reference page.