ABB TA, TF and E-Series Overload Relays: Full Range Review
What is the ABB overload relay range built around? ABB splits its thermal overload protection into two families: the TA/TF bimetallic line, tested to IEC 60947-4-1 Class 10A and calibrated to trip within 2-10 s at 7.2x the set current from cold, and the E-series electronic line, which reads current through internal CTs and lets a technician pick Class 10, 20 or 30 on the same unit. A TA relay clipped to an undersized contactor nuisance-trips on every start; an E-series unit sized wrong does the same thing with a display instead of a dial. This review covers the TA bimetallic range (TA25DU through TA200DU and larger frames), the TF42 compact relay for AF09-AF38 contactors, the E-series electronic line (EF19 to EF460), setting ranges, trip class options, and where each series stops making sense.
ABB TA Bimetallic Overload Relays: TA25DU to TA200DU
The TA line covers ABB's bimetallic overload relays from small frame sizes up to roughly 200 A, clipping directly onto the A-line and AF-line contactors without separate wiring for the current path. TA25DU handles motors up to about 25 A FLC; TA42DU, TA75DU, TA80DU, TA110DU and TA200DU step the range up in roughly the same pattern as the contactor frames they mount to. Each is Class 10A out of the box, ambient-compensated between about -5 and +55 C, and phase-loss sensitive by construction, since the differential trip bar reacts faster to a lost phase than to a slow, balanced overload. Reset is field-selectable between hand and auto, and every unit carries the standard 95-96 NC / 97-98 NO contact pair plus a STOP/TEST button.
What ties the range together is the mounting system, not the current rating. A TA75DU under an A75 contactor and a TA200DU under an A210 both use the same base clip and the same terminal marking scheme, so a panel builder standardizing on the TA line does not retrain wiring crews as motor sizes climb. Contactors and their matching TA relay share a part-number logic ABB has kept stable across generations, which is one reason the line still dominates general-purpose motor starting above 25 A.
ABB TF42: Compact Overload Relay for AF09-AF38 Contactors
TF42 is the bimetallic relay for ABB's compact AF-line contactors (AF09 through AF38), covering roughly 0.1 A to 38 A depending on the insert used. It shares the Class 10A trip curve, ambient compensation and phase-loss sensitivity of the TA line, but the mechanical interface is built for the AF frame's smaller footprint. It does not fit under an A-line contactor, and a TA relay does not fit under an AF-line one. For panels built entirely on AF contactors, common in compact starter and MCC drawer designs, TF42 keeps the mounting depth down without giving up any of the TA line's protection logic.
What we see in the field: builders standardizing a whole MCC lineup on AF contactors for space reasons sometimes forget TF42 tops out at 38 A, and end up mixing in an A-line frame plus TA75DU for the handful of larger motors on the same lineup. That is a legitimate mixed-frame design, not a mistake, but it means the BOM carries two mounting families instead of one.
ABB E-Series Electronic Overload Relays: EF19 to EF460
The E-series replaces the bimetal strip with current transformers feeding a microcontroller, and the range runs EF19, EF45, EF65, EF96, EF146, EF205, EF370 up to EF460, eight frame sizes covering roughly 0.4 A to 460 A. Setting ratio widens to about 1:3 or 1:4, versus roughly 1:1.5 on a TA bimetal relay, so a single EF146 might cover a setting window a TA line would need two or three separate relays to span. Trip class is selectable, Class 10, 20 or 30 on the same physical unit, instead of being fixed at manufacture.
Beyond the wider range, the E-series adds protection functions the bimetal line does not have at all: true phase-loss detection, not just the differential trip-bar effect, phase-imbalance monitoring, stall and locked-rotor trip, and on the larger frames, ground-fault detection. Some models accept a thermistor input, reading the motor's own embedded PTC sensor directly instead of inferring winding temperature from line current. Thermal memory persists through a power cycle, so a relay that trips hot and gets reset immediately after a control-power blip still knows the motor was hot.
Trip Class and Setting Range Across the ABB Line
Trip class is defined the same way across TA, TF and E-series, because all three certify to IEC 60947-4-1: hold the relay at 7.2 times its current setting from a cold start, and measure the time to trip.
Formula: Trip class verification — Source: IEC 60947-4-1, Table 4
t_trip (at I = 7.2 × I_set, from cold) falls within [t_min, t_max] for the declared class
| Symbol | Description | Unit |
|---|---|---|
| I_set | Current dial setting (target: motor FLC) | A |
| t_trip | Measured trip time at 7.2× I_set from cold | s |
| Class 10A | Trip window at 7.2× setting | 2-10 s |
| Class 20 | Trip window at 7.2× setting | 6-20 s |
TA and TF relays ship fixed at Class 10A, 2 to 10 s at 7.2x setting, which fits standard pumps, fans and machine-tool motors whose run-up finishes in a few seconds. E-series relays let a technician dial in Class 10, 20 or 30 on the same body, which matters for high-inertia loads: a large centrifugal fan or a crusher can take 15-25 s to reach full speed, and a Class 10 relay reads that run-up as an overload and trips before the motor is even up to speed. See overload relay trip classes 10A, 10, 20 and 30 for the full breakdown of where each class fits.
Phase-Loss, Ground-Fault and Stall Protection by Series
Every ABB overload relay in this review is phase-loss sensitive to some degree, but the mechanism differs. TA and TF rely on the differential trip bar: a lost phase pushes roughly 1.7x current onto the two remaining windings, and the bar reacts to the imbalance between the three bimetal strips faster than the plain thermal element would react to the raw overload. E-series measures phase current directly through its CTs and can flag an imbalance well before it reaches a trip-worthy overload, which is a meaningfully earlier warning on motors that run lightly loaded most of the time.
Ground-fault detection and locked-rotor or stall trip exist only on the E-series, and only on part of that range. Check the specific EF model rather than assuming every E-series unit carries every function. This is where the line stops being a straight step-up in current rating and starts being a step-up in what the relay actually knows about the motor.
Choosing Between TA, TF42 and E-Series
The decision usually starts with the contactor already on the BOM, not the relay. TA follows A/AF-line contactors above the TF42 window; TF42 follows the compact AF09-AF38 frames; E-series follows whichever contactor frame is spec'd once the application calls for selectable trip class, a wide setting ratio, or ground-fault/stall protection the bimetal line cannot provide.
| Criteria | TA (bimetallic) | TF42 (bimetallic) | E-series (electronic) |
|---|---|---|---|
| Setting range | Up to ~200 A | ~0.1-38 A | ~0.4-460 A |
| Setting ratio | ~1:1.5 | ~1:1.5 | ~1:3 to 1:4 |
| Trip class | Fixed 10A | Fixed 10A | Selectable 10/20/30 |
| Mounts to | A/AF-line contactors | AF09-AF38 contactors | Varies by frame |
| Extra protection | Phase-loss (differential) | Phase-loss (differential) | True phase-loss, imbalance, stall, ground-fault (frame-dependent) |
Some builders default to E-series across the board because the extra functions are there if needed later; others hold the line at TA or TF42 for anything with a short, predictable run-up, since the fixed Class 10A relay costs less and has no configuration step to get wrong at commissioning. Both are defensible; the split depends on how much the plant's motor mix leans toward high-inertia loads. For a cross-brand view of where TA sits against Schneider's TeSys LRD and Siemens SIRIUS 3RU2, see the Schneider LRD vs ABB TA vs Siemens 3RU2 comparison, and for the broader ranking across brands see best thermal overload relay brands ranked.
All three ABB families share the SCPD-plus-contactor-plus-overload-relay starter architecture common to every brand. For the fuse or motor protection circuit breaker that has to sit upstream and clear the short circuit the overload relay does not, and for the full sizing and coordination logic behind all of it, see the thermal overload relay engineering guide. Stock across the current thermal overload relays range spans TA25DU through the larger E-series frames. For the same review structure applied to Siemens, see Siemens SIRIUS 3RU2 and 3RB3 range review.
Frequently Asked Questions
What does TA25DU mean in ABB's overload relay naming?
TA is the bimetallic overload relay series, and the number after it is the setting frame; TA25DU is the frame sized for the low end of the range, up to roughly 25 A FLC. The DU suffix denotes the standard direct-mount version.
Can a TF42 relay mount under an A-line contactor?
No. TF42 is built for the AF09-AF38 compact contactor frame and does not share a mounting clip with the A-line contactors that take TA relays. Mixing the two requires a different relay choice, not a direct swap.
Is E-series more accurate than TA for a standard pump motor?
Not necessarily. For a motor with a short, predictable run-up and no need for ground-fault or stall detection, a fixed Class 10A TA relay does the job at lower cost and with nothing to configure. E-series earns its price on high-inertia loads or where the extra protection functions matter.
What is the setting ratio on ABB E-series relays?
Roughly 1:3 to 1:4 depending on the EF model, meaning the top of the dial is three to four times the bottom setting. That is wider than the roughly 1:1.5 ratio on TA and TF42, so one E-series unit can replace two or three bimetal relays across a motor size range.
Does the ABB E-series support thermistor input?
Some E-series models accept a direct PTC thermistor input from the motor winding, reading actual winding temperature instead of inferring it from line current through a CT. Check the specific EF model, since the function is not on every frame in the range.
Which ABB overload relay class fits a high-inertia fan?
Class 20 or 30, selected on an E-series unit, generally fits fans and centrifuges with a run-up over about 10 s. A fixed Class 10A TA or TF42 relay will nuisance-trip on the same load before it reaches full speed.
Conclusion
ABB's overload relay range is really two decisions stacked on top of each other. First, the contactor frame narrows the choice to TA, TF42, or an E-series body sized to match. Second, the application decides whether a fixed Class 10A bimetal relay is enough, or whether the selectable trip class, wider setting ratio and extra protection functions on E-series are worth the added cost and the configuration step. For general-purpose motors with short run-ups, TA and TF42 remain the simpler, cheaper answer. For high-inertia loads, motors that need ground-fault or stall detection, or panels where one relay body replacing several bimetal frames simplifies the spares list, E-series is the better fit.
