Best Thermal Overload Relay Brands Ranked
Which thermal overload relay brand ranks best? No single brand wins on every axis: Schneider Electric's TeSys LRD covers the widest bimetallic setting range (roughly 0.10 A to 630 A across LRD and LR9F), ABB's E-series pushes the deepest electronic feature set (EF19 through EF460, 1:3-1:4 setting ratio), and Siemens SIRIUS 3RU21/3RB30 ties overload data most tightly into a full load-feeder system with 3RT2 contactors and 3RV2 MPCBs. The right choice depends on which variable matters for the job — frame coverage, protection depth, or coordination documentation — because picking on brand loyalty alone forces a rework once the motor data sheet lands. This article ranks the three against each other on setting range, trip class options, phase-loss and ground-fault sensing, reset behavior, coordination data, and how fast the part actually ships.
How This Ranking Was Built
Six criteria, each pulled from the manufacturer's own catalog and IEC 60947-4-1 coordination tables, not marketing copy: setting range and frame breakpoints, trip class selection (fixed vs selectable), phase-loss sensitivity, extra protections on the electronic line, published Type 1/Type 2 coordination data, and mounting compatibility with the brand's own contactor family. Price is deliberately excluded — landed cost swings by market and distributor, and a relay that is 10% cheaper but under-protects a $4,000 motor is not a saving. What follows compares thermal overload relays from all three brands directly, with a link to the full thermal overload relay engineering guide for anyone starting from zero.
Setting Range and Frame Coverage
Schneider's TeSys LRD bimetallic line runs from about 0.10 A up to roughly 12 A on the small D-frame parts, with LR9F extending coverage to 630 A on the larger frames — the broadest single-family span of the three. ABB's TA line (TA25DU through TA200DU and up) tops out near 200 A in bimetal before you move to the CT-fed E-series for anything larger. Siemens 3RU21 bimetal spans frame sizes S00 through S3, capping around 100 A, after which 3RB30/3RB31 electronic units take over. In practice: if the motor is under 12 A, all three have a direct-fit bimetal option under their own contactor. Past 100-200 A, Schneider's LR9F still offers a bimetal path where ABB and Siemens have already switched you to electronic.
Trip Class: Fixed vs Selectable
All three bimetallic lines ship as Class 10A or Class 10, tested per IEC 60947-4-1 at 7.2x the current setting from cold.
Formula: Trip Class Test Point — Source: IEC 60947-4-1, Table 12
ttrip = time to trip at I = 7.2 x Iset, relay at cold start
| Symbol | Description | Unit |
|---|---|---|
| ttrip | Trip time at the test multiple | seconds |
| Iset | Current dial setting (= motor FLC) | A |
| Class 10A | Trips in 2-10 s | - |
| Class 10 | Trips in 4-10 s | - |
| Class 20 / 30 | Trips in 6-20 s / 9-30 s | - |
Where the brands split is on selectable class in the electronic line. Siemens 3RB31 offers Class 5, 10, 20 and 30 on a single unit — the widest spread of the three, useful when one stock unit has to cover both a standard pump and a high-inertia fan on the same job. ABB's E-series covers Class 10/20/30 selectable. Schneider's LR9/TeSys T electronic overload also runs selectable class with a wide setting ratio, though its catalog leans more toward setting-range flexibility than class count. None of the pure bimetallic lines (LRD, TA, 3RU21) let you change class in the field — they ship fixed at Class 10A or 10, so a high-inertia load on a bimetal relay means ordering a different part, not flipping a dial. See overload relay trip classes 10A, 10, 20 and 30 for the full breakdown.
Phase-Loss, Ground-Fault and Extra Protections
Bimetal phase-loss protection is close to a wash across the three — LRD, TA and 3RU21 all build in a differential trip bar that reacts to the imbalance, not just total heat. The gap opens on the electronic side. Siemens 3RB31 adds ground-fault detection on top of phase-loss, a feature ABB's E-series and Schneider's LR9 do not carry as standard. ABB's E-series counters with a thermistor input on several models (EF65 and up), letting the relay trip on a winding RTD/PTC signal instead of relying only on current — useful on motors with embedded temperature sensors. Schneider's LR9/TeSys T sticks closer to the core spec: wide setting ratio, selectable class, phase-loss, thermal memory, without stacking on ground-fault or thermistor inputs. What we see in the field: ground-fault detection matters most on long feeder cables in wet or corrosive areas, where insulation breakdown is the more likely fault mode than a simple overload.
Reset, Coordination Data and Contactor Fit
Reset options are identical in substance: hand (manual) or auto, selectable by a switch or a small screw, across LRD, TA and 3RU21. Where the three actually differ is in how deep and how public the coordination tables go. Schneider and Siemens both publish extensive Type 1 and Type 2 coordination tables pairing their overload relays with their own contactors (LC1D with LRD; 3RT2 with 3RU21/3RB3) and upstream motor protection circuit breakers or fuses, so a panel builder can pull a table and get a certified Type 2 combination without independent testing. ABB's tables cover the same ground for its A/AF contactor + TA/E-series pairings, but the SIRIUS ecosystem — 3RT2 contactor, 3RU21/3RB3 overload, 3RV2 MPCB, all snapping together mechanically — is the tightest of the three when the panel also needs the compact combined footprint. For the underlying logic, see overload relay Type 1 vs Type 2 coordination.
Brand-by-Brand Comparison
| Criteria | Schneider TeSys LRD/LR9 | ABB TA/E-series | Siemens SIRIUS 3RU2/3RB3 |
|---|---|---|---|
| Bimetal setting range | 0.10-630 A (LRD + LR9F) | Up to ~200 A (TA line) | Up to ~100 A (3RU21, S00-S3) |
| Electronic setting ratio | Wide (LR9/TeSys T) | 1:3 to 1:4 (E-series) | Up to 1:4 (3RB30/31) |
| Selectable trip class | Yes, on LR9/TeSys T | Yes, Class 10/20/30 | Yes, Class 5/10/20/30 |
| Ground-fault detection | Not standard | Not standard | Yes, on 3RB31 |
| Thermistor/RTC input | Not standard | Yes, EF65 and up | Not standard on 3RU2/3RB3 |
| Native contactor line | LC1D (TeSys D) | A/AF contactors | 3RT2 |
| Coordination table depth | Extensive, published | Extensive, published | Extensive, tightest MPCB tie-in |
Which Brand Ranks Best for Which Job
For raw setting-range coverage on a mixed inventory of small and large motors, Schneider's LRD/LR9F combination wins — one family, one mounting logic, from fractional-amp control motors to 630 A. For the deepest electronic feature set on a single motor with embedded temperature sensing, ABB's E-series ranks first on the thermistor input. For a panel that needs the tightest documented coordination between the manual motor starter/MPCB, contactor and overload relay, plus ground-fault detection in one electronic unit, Siemens 3RB31 with SIRIUS ranks first. None of the three is wrong; the ranking flips depending on whether the job optimizes for range, features, or coordination paperwork. Some builders standardize on one brand across the whole panel purely to keep the coordination tables valid and simplify spares — a defensible reason to rank a brand first even if a rival edges it on a single spec sheet.
All three sit under the same core mechanism regardless of rank: a dial set to motor FLC, a differential bimetal or CT sensing element, and a 95-96 NC contact that drops the contactor coil on trip. Anyone new to the device should start with what a thermal overload relay is and how it works before comparing brands, and anyone choosing between the bimetal and CT-fed lines should read thermal vs electronic overload relays first.
Frequently Asked Questions
Which thermal overload relay brand has the widest setting range?
Schneider's TeSys LRD/LR9F combination spans roughly 0.10 A to 630 A in bimetallic form, the widest single-family bimetal range of the three brands compared here. ABB's TA line and Siemens' 3RU21 both top out lower before requiring a switch to an electronic (CT-fed) unit.
Are ABB, Schneider and Siemens overload relays interchangeable?
Not directly. Each brand's overload relay mounts mechanically under its own contactor (LRD under LC1D, TA/TF under A/AF, 3RU21 under 3RT2), and published Type 1/Type 2 coordination data only applies to same-brand combinations. Cross-brand pairing is possible with separate mounting hardware but voids the manufacturer's coordination claim.
Which brand's electronic overload relay has ground-fault detection?
Siemens' 3RB31 includes ground-fault detection as a standard feature alongside phase-loss and selectable Class 5/10/20/30. ABB's E-series and Schneider's LR9/TeSys T do not carry ground-fault detection as a standard function.
Do all three brands publish Type 2 coordination tables?
Yes. Schneider, ABB and Siemens each publish coordination tables pairing their overload relays with their own contactors and upstream short-circuit protective devices, rated to either Type 1 or Type 2 per IEC 60947-4-1. The tables are brand-specific and do not carry over to mixed-brand starters.
Which brand is easiest to source quickly for a panel build?
This depends more on distributor stock than brand engineering. Standard bimetallic sizes (LRD, TA25DU-TA110DU, 3RU21 S00-S2) are common stock items across most industrial distributors; larger frames and electronic units with less common settings often carry longer lead times regardless of brand.
Conclusion
Ranking thermal overload relay brands only makes sense against a specific job, not in the abstract. Schneider leads on bimetallic setting-range breadth, ABB leads on electronic feature depth with thermistor input, and Siemens leads on tight coordination between the overload relay, contactor and MPCB in one documented system. Match the criterion that matters for the panel in front of you — range, features, or paperwork — and the ranking answers itself.
