Thermal Overload Relay Price List: ABB, Schneider, Siemens Compared
What determines the price of a thermal overload relay? Frame size, current-setting range, bimetallic-versus-electronic construction, and the mounting ecosystem that ties the relay to a specific contactor family set the price tier across ABB, Schneider Electric, and Siemens catalogs, more than the brand name on the box. Buy the wrong frame or the wrong reset mode and the difference is not a discount — it is a relay you have to re-source before the panel ships. This guide works through the price drivers in order: frame and current range, the bimetallic-to-electronic cost gap, trip-class pricing, accessories that add to the line item, brand positioning, and how to buy the correct part on the first order.
What Sets the Base Price: Frame Size and Current Range
A bimetallic relay is priced by the frame it clips onto and the current range it covers, not by a marketing tier. ABB's TA25DU sits at the small end, mounting under A-line miniature contactors, and TA42DU, TA75DU, TA80DU, TA110DU, and TA200DU step up in frame as the setting range climbs toward roughly 200 A. Schneider's LRD family runs the same ladder under LC1D (TeSys D) contactors from about 0.10 A through the mid-range, with LR9F taking over on the larger frames toward 630 A. Siemens' 3RU21 covers frame sizes S00, S0, S2, and S3 up to roughly 100 A, mounting straight onto 3RT2 contactors.
Small-frame vs large-frame breakpoints
A relay at the bottom of a frame's range and one at the top of the same frame carry the same list price — the frame, not the amp setting inside it, is what the catalog prices. Step across a frame breakpoint, say from a 25 A frame to a 42 A frame, and the price moves with it even if the motor current only crept up by a few amps. Buying a relay one frame size larger "for headroom" is a quiet way procurement pays more than the motor needs.
Bimetallic vs Electronic: Why Electronic Costs More
Electronic (solid-state) overload relays cost more per frame than their bimetallic equivalent because they replace three heated bimetal strips with current transformers or shunts feeding a microcontroller board. That board is what buys the wider setting ratio, often 1:3 to 1:4 versus about 1:1.5 on a bimetal unit, a selectable trip class instead of a fixed one, and extra protections bimetal cannot offer: true phase-loss, phase-imbalance, stall/locked-rotor, ground-fault, and thermal memory that survives a power cycle. ABB's E-series (EF19 through EF460), Schneider's LR9 / TeSys T, and Siemens' 3RB30/3RB31 sit in this tier. If none of those extra protections is specified for the application, the price premium buys nothing the panel actually uses — worth raising in a design review before the part number goes on the BOM.
For the full functional trade-off behind the price gap, see thermal vs electronic overload relays.
Trip Class 10A, 10, 20, and 30: Does a Higher Class Cost More?
On a bimetallic relay the trip class is usually fixed at the factory, most often 10A, sometimes 10, so class is not a separate line item — the catalog number carries the class. On an electronic relay the class (5/10/20/30 depending on brand) is a dial or switch selection on the same part number, so a Class 30 setting for a high-inertia fan uses the same board as a Class 10 setting for a pump. What actually adds cost there is the wider setting ratio and the microcontroller, not the class number itself. Background on the class values: overload relay trip classes 10A, 10, 20, and 30.
Formula: Trip-class test condition — Source: IEC 60947-4-1, Clause 7 (trip-class characteristics)
I_test = 7.2 × I_set, applied from cold
| Symbol | Description | Unit |
|---|---|---|
| I_test | Test current applied from cold to verify trip class | A |
| I_set | Current dial setting (= motor FLC) | A |
| t_trip | Time to trip at I_test — Class 10A: 2-10 s, Class 10: 4-10 s, Class 20: 6-20 s, Class 30: 9-30 s | s |
Accessories That Add to the Line Item: Reset Selector, Terminals, Mounting Kits
The relay body is rarely the whole purchase order line. A hand/auto reset selector, a separate stop/test pushbutton kit, ring-terminal or box-terminal adapters, and, critically, the mounting adaptor that lets the relay clip onto a specific contactor frame are usually separate catalog numbers. ABB, Schneider, and Siemens each sell the overload relay as part of a load-feeder ecosystem: TA and TF need matching frame adaptors under A/AF contactors, LRD needs the LC1D base, and 3RU21 either clips directly onto 3RT2 or needs a stand-alone mounting kit. Buy the relay without checking mounting compatibility and the apparent savings evaporate into an extra line item and a shipping delay. See contactors for the matching frames these relays snap onto.
ABB TA vs Schneider LRD vs Siemens 3RU2: Price Positioning by Brand
None of the three is the budget brand in an absolute sense. Each prices its own bimetallic-to-electronic ladder the same way: low on the bimetal tier, stepped up on the electronic tier. What actually separates the three at the counter is ecosystem lock-in — once a panel is built on LC1D contactors, an LRD is nearly always cheaper to source and stock than adapting a TA or 3RU21 onto the same base. Brand preference on the overload relay is, in practice, contactor-frame preference in disguise.
| Criteria | ABB (TA / E-series) | Schneider (LRD / LR9) | Siemens (3RU21 / 3RB3) |
|---|---|---|---|
| Bimetallic range | TA25DU-TA200DU, up to ~200 A | LRD low end, LR9F to ~630 A | 3RU21, frames S00-S3, up to ~100 A |
| Compact-contactor line | TF42 (AF09-AF38) | LR2K/LR3K (TeSys K) | 3RU21 S00 on 3RT201x |
| Electronic tier | EF19-EF460, 1:3-1:4 ratio | LR9 / TeSys T | 3RB30/3RB31, ~1:4 ratio, ground fault on 3RB31 |
| Mounting ecosystem | Snaps under A/AF contactors | Snaps under LC1D (TeSys D) | Snaps onto 3RT2 (SIRIUS load feeder) |
| Where the premium sits | E-series ground fault, thermistor input | LR9 wide range, TeSys T selectable class | 3RB31 ground-fault detection |
For how the three brands compare across the full load-feeder rather than the relay alone, see the thermal overload relay engineering guide.
How to Avoid Over-Buying: Matching the Relay to the Motor
The single biggest cost lever isn't brand — it's buying the setting range the motor actually needs. The dial is set to the motor's FLC from the nameplate, not to the breaker or contactor rating sitting next to it in the panel, per how to select and set an overload relay for a motor. Buying a relay whose range center sits far above the actual FLC means paying for setting resolution that never gets used, and on some electronic lines it can push the order into a larger CT tier for no operational benefit. What we see in the field: on star-delta jobs, sizing off the line current instead of the delta-leg current is the most common way a panel builder ends up one frame larger than necessary — the relay in the delta leg sees roughly 0.58x the line FLC, not the full line current.
Buying the three devices as a manufacturer-published coordination set, rather than mixing brands to shave a line item, also avoids re-testing costs. See motor protection circuit breakers for the SCPD half of that set. An overload relay bought outside the published coordination table may still work, but the declared Type 2 rating disappears with it.
Where to Buy Overload Relays Without Paying for Extra Steps
Because the overload relay is one line in a three-device starter, sourcing the SCPD, contactor, and overload relay from a single stock cuts freight and lead-time costs that never show up on the relay's own price tag. Panels that swap in a manual motor starter in place of a separate fuse-plus-relay combination shift the comparison again — see manual motor starters for that alternative topology. Browse the current thermal overload relays range by brand and frame before a part number goes onto a BOM, and check where to buy thermal overload relays online for lead-time and stock notes across the three brands.
Frequently Asked Questions
Does a higher trip class cost more on a bimetallic relay?
No. Trip class on a bimetallic relay is fixed by the catalog number, not a paid upgrade. On an electronic relay, class is a switch setting on the same board, so Class 30 and Class 10 on the same frame carry the same price.
Is an electronic overload relay significantly more expensive than a bimetallic one?
Yes, for the same frame, because it replaces bimetal strips with a current-sensing and microcontroller board. The premium buys a wider setting ratio, selectable class, and extra protections like ground-fault and thermal memory — worth it only if the application uses them.
Why do accessories add so much to the total line item?
The reset selector, terminal adapters, and especially the mounting kit that clips the relay to its contactor are usually separate catalog numbers. Skipping the compatibility check on the mounting kit is the most common way a "cheap" relay order gets delayed.
Does buying a larger current range than needed save money later?
Rarely. It usually means paying for a bigger frame or, on electronic lines, a larger CT tier, without any operational benefit — the dial should be set to the motor's nameplate FLC, not to a margin "for headroom."
Can I mix brands across the SCPD, contactor, and overload relay to cut cost?
Only if the resulting set still matches a manufacturer-published coordination table. Mixing outside that table can void the declared Type 1 or Type 2 coordination rating even if every device works individually.
Where can I buy ABB, Schneider, and Siemens overload relays with fast delivery?
Stoklink stocks and cross-references all three brands' bimetallic and electronic lines by frame and current range, alongside the matching contactors and MPCBs for a coordinated starter set.
Conclusion
The price of a thermal overload relay tracks frame size, current range, and bimetallic-versus-electronic construction before it tracks brand. Buy to the motor's nameplate FLC, confirm the mounting adaptor matches the contactor already on the BOM, and treat the electronic tier's premium as a purchase of specific extra protections, not a general upgrade. Priced that way, ABB, Schneider, and Siemens land in the same range for the same frame — the real cost difference shows up when the wrong frame, class, or mounting kit has to be re-ordered after the panel is already on the bench.
