Siemens 3RT vs Eaton DILM Contactor Comparison: Specs, Sizing and Selection Guide

What is a Siemens 3RT vs Eaton DILM contactor comparison? A Siemens 3RT versus Eaton DILM contactor comparison is a head-to-head evaluation of two IEC 60947-4-1-rated AC motor switching device families, spanning roughly 9 A to 1,000 A, across overlapping frame sizes where both manufacturers compete directly in industrial control panels. Selecting the wrong contactor — mismatched utilization category (AC-3 vs AC-4), insufficient SCCR coordination, or incompatible coil dropout voltage — risks nuisance dropout, fault damage, or failed UL 508A panel certification. This guide covers frame size and current rating overlap, coil pickup and dropout behavior, short-circuit coordination and SCCR ratings, accessory modularity, field serviceability, and regional pricing and lead time differences.

Published: 2026-04-27 | Last updated: 2026-04-27 | By Stoklink Engineering Team

Why this comparison matters in panel design

In our experience working with OEM panel shops, the Siemens 3RT vs Eaton DILM debate comes up on nearly every AC motor starter project rated between 7.5 kW and 250 kW. Both families are IEC 60947-4-1 compliant, both offer solid-state coil electronics in the mid and upper frames, both publish a clear AC-3 rating on every frame, and both have 100 kA SCCR (Short-Circuit Current Rating) ratings available when combined with the matching motor protection circuit breaker. So why do engineers still agonize over the choice?

Because the devil lives in the accessories. Auxiliary contact blocks, surge suppressors, mechanical interlocks, wiring kits for reversers and star-delta starters — these are where the two ecosystems diverge significantly in cost, lead time, and panel real estate. A 30% price delta on the contactor itself can flip entirely when you add four auxiliary blocks, a timer, and a mechanical interlock.

We've seen procurement teams standardize on one family based on a single spreadsheet comparison, only to discover six months later that their regional distributor stocks the other brand's accessories three weeks faster. That kind of mistake costs real money on shutdown jobs.

For authoritative definitions of the AC-3 rating and other utilization categories for low-voltage contactors and motor-starters, refer to the IEC 60947-4-1 international standard.

Frame sizes and current ratings: where they actually compete

Both manufacturers organize their contactors into frame sizes, but the increments differ — and so do the AC-3 rating steps within each range. Understanding the overlap and gaps matters when you're trying to standardize across a plant.

Siemens 3RT2 frame range

The Siemens 3RT2 series spans Size S00 through Size S14. Size S00 (3RT2015 to 3RT2018) covers 7 A to 18 A AC-3 at 400 V. Size S0 (3RT2023 to 3RT2028) handles 9 A to 38 A. Size S2 reaches 50 A, Size S3 hits 80 A, and the progression continues: S6 (185 A), S10 (300 A), S12 (500 A), S14 (780 A). The jump points are at 38 A, 50 A, 80 A, and 150 A — these are the thresholds where you change frame and often change terminal type (screw to box lug).

Eaton DILM frame range

The Eaton xStart DILM series runs from DILM7 (7 A) through DILM2200 (2200 A). The key frames for industrial motor starting are DILM7, DILM9, DILM12, DILM17, DILM25, DILM32, DILM40, DILM50, DILM65, DILM80, DILM95, DILM115, DILM150, DILM170, DILM185, DILM225, DILM250, DILM300, DILM400, DILM500, DILM580, DILM650, DILM750, DILM820, DILM1000, DILM1400, DILM1600, DILM2200. The numeric suffix indicates the AC-3 rating in amperes at 400 V — a genuinely useful naming convention.

Eaton's granularity in the 7 A to 50 A range gives engineers more options to size precisely to the motor FLA (Full Load Amps) without oversizing. Siemens S00/S0 covers the same range with fewer SKUs, which simplifies inventory but sometimes forces you up a frame.

Coil voltages, pickup, and dropout behavior

A common mistake is assuming coil voltage tolerance is identical across brands just because the AC-3 rating on the nameplate matches. It isn't, and the difference matters in plants with weak PLC 24 VDC supplies or long control cable runs where voltage drop is real.

Siemens 3RT2 coil characteristics

Siemens 3RT2 AC coils operate at 0.8 to 1.1 × Us (rated control supply voltage) per IEC 60947-4-1 §8.2.1.2. DC coils on frames S00 through S3 use electronically controlled coil technology (the "EE" suffix on part numbers like 3RT2026-1BB40), which reduces holding power to roughly 2 W and extends tolerance to 0.7–1.25 × Us. Pickup time is typically 25–40 ms; dropout is 10–20 ms on standard coils.

Eaton DILM coil characteristics

Eaton DILM uses the same IEC-compliant 0.8–1.1 × Us tolerance as standard. The DILM7 through DILM38 frames use AC or DC operated coils with the DILA and DILM numbering. What we typically see in the field: Eaton's wide-range electronic coils (marked "G" in the coil code, e.g., DILM17-10(24VDC)) tolerate 0.7–1.2 × Us and draw approximately 1.5 W holding power. Pickup time is 15–30 ms, closer to the faster end than Siemens standard coils.

On PLC-driven panels with lots of contactors switching simultaneously, the DILM's lower holding power can save you from having to upsize the 24 VDC power supply. We specced a 40 A DC power supply down to 25 A on one food processing line just by switching coil families. Not always decisive, but real.

Short-circuit coordination and SCCR ratings

Coordination tables are published by both manufacturers and they are non-negotiable documents. Per IEC 60947-4-1 Clause 9.3.4, Type 2 coordination means "no damage" to the contactor after a short circuit — the contactor and overload relay must remain suitable for further service at their original AC-3 rating. Type 1 allows damage but no hazard.

Siemens 3RT coordination

Siemens publishes coordination tables combining 3RT2 contactors with 3RV2 motor protection circuit breakers and 3NA fuses. A typical Type 2 pairing: 3RT2026 + 3RV2021-4BA10 gives 65 kA at 400 V. With fuses (gG class), the 3RT2026 achieves 100 kA when protected by a 50 A NH00 gG fuse.

Eaton DILM coordination

Eaton pairs DILM contactors with PKZM0 and PKE motor protective circuit breakers. DILM25 + PKZM0-25 delivers 65 kA at 400 V Type 2. DILM32 + PKE32 reaches 100 kA with the right upstream fuse. Eaton also publishes UL 508A Type E self-protected combination ratings — useful if you're exporting panels to North America.

Accessories, modularity, and field serviceability

In our experience, the single biggest driver of total installed cost — once the AC-3 rating is correctly matched — is accessory ecosystem depth. Here's where the brands diverge sharply.

Auxiliary contact blocks

Siemens 3RT2 uses the 3RH29 series auxiliary blocks — front-mounted (1, 2, or 4 contacts) and side-mounted (2 or 4 contacts). Siemens contactors from S00 upward include one built-in auxiliary (NO or NC) on frames S2 and larger, which often eliminates the need for a block on simple logic. The snap-on action is firm and repeatable.

Eaton DILM uses DILM-XHI auxiliary blocks. You get front-mount (2 or 4 contacts) and side-mount (2 or 4 contacts) options. Eaton's auxiliary blocks are slightly narrower, which saves about 5 mm on panel width on dense MCC layouts. A small thing that adds up when you're building 40-bucket MCCs.

Surge suppressors and coil interface

Both brands offer RC, varistor, and diode suppressors. Siemens 3RT29 series suppressors plug directly onto the coil terminals. Eaton uses DILM-XSP series with the same approach. The functional difference is negligible. However, Eaton's DILM contactors starting at DILM7 can accept the XSPR suppressor with LED indicator, which is useful for troubleshooting.

Mechanical and electrical interlocks for reversers

This is where Siemens has historically led. The 3RA2 reversing assembly kits (3RA2913-2AA1 for S00, for instance) come as pre-wired, pre-interlocked assemblies. You mount, add coil voltage, and wire the motor — done. Eaton offers DILM-XRM mechanical interlocks and pre-assembled reverser combinations (DIUL series), but the SKU range is narrower.

Price, lead times, and regional availability

Prices fluctuate, so take these as directional. In Europe, a Siemens 3RT2026-1AP00 (25 A AC-3 rating, 230 VAC coil) lists around €75–85 from authorized distribution. The comparable Eaton DILM25-10(230V50HZ) runs €70–80. Net-net, close to parity.

In the Gulf and Southeast Asia, Eaton typically has stronger stock depth because of the Moeller legacy distribution network. In Germany, Austria, and Switzerland, Siemens has a clear home-field stocking advantage. In North America, both brands ship from US warehouses with comparable lead times, but Eaton's integration with Cutler-Hammer legacy product lines gives it an edge in retrofits.

Sizing walkthrough: a 45 kW pump motor example

Let's work through a realistic sizing exercise. A 45 kW, 400 V, 50 Hz centrifugal pump motor with nameplate FLA of 84 A, operating 14 hours/day, installed in a panel with 50 °C internal ambient, requiring an AC-3 rating duty (direct-on-line start, infrequent).

Applying the sizing formula: I_e ≥ 84 × 1.0 × 1.05 = 88.2 A

Siemens candidate: 3RT2037-1AP00 at 65 A AC-3 is too small. Next frame up: 3RT2038-1AP00 at 80 A AC-3 — still marginal. Step to 3RT2045-1AP00 at 80 A? No, 3RT2045 is rated 80 A. The correct choice is 3RT2046-1AP00 at 95 A AC-3. Comfortable margin.

Eaton candidate: DILM95(230V50HZ) at 95 A AC-3 — identical fit. Alternatively, DILM80 at 80 A would be undersized given the ambient derating.

For the overload relay: Siemens 3RU2146-4KB0 (62–73 A range — no, too small). Use 3RU2146-4LB0 (70–90 A). Eaton: ZB150-100 or PKE equivalent for motor protection.

Comparison matrix: Siemens 3RT vs Eaton DILM vs ABB AF

Including ABB AF gives useful context since many engineers cross-shop all three at the same AC-3 rating points. ABB AF series uses wide-range electronic coils as standard across all frames — a genuine differentiator.

Installation contactors: a different beast

Motor contactors like 3RT and DILM are selected on AC-3/AC-4 duty, with the AC-3 rating being the primary sizing reference. Installation contactors — used for lighting loads, heaters, and resistive circuits in distribution boards — are AC-1/AC-7 rated and have different selection logic. Engineers often overlook this category when specifying building services panels.

For typical DIN-rail installation contactor applications (lighting, HVAC starters, electric heating), the ABB ESB series is a reference product. You can see the range in the Stoklink catalog: the ABB 1SBE111111R0611 ESB16-11N-06 16A 2P 230V 1NO+1NC covers small lighting circuits, while the ABB 1SAE231111R0622 ESB25-22N-06 25A 4P handles heavier four-pole loads. For DC coil control requirements, the ABB 1SBE111111R0602 ESB16-02N-06 with 230V DC coil is a common spec in telecom and rail applications.

Stepping up to higher currents, the ABB ESB25-31N-06 (25 A, 3NO+1NC) and the ABB ESB25-40N-06 (25 A, 4NO) cover HVAC and commercial heating panels. For industrial heating banks and 400 Hz aircraft ground power applications, the ABB ESB40-40N-06 at 40 A and the ABB ESB63-40N-06 at 63 A are the workhorses. The 400 Hz rating on the ABB ESB63-31N-06 specifically targets aviation ground support equipment.

Real-world case: cement plant bag filter retrofit

In 2022 we supported a cement plant in North Africa retrofitting 64 bag filter shaker motors (2.2 kW each) across two MCCs. The original 1998-vintage panels used Telemecanique LC1-D09 contactors, all obsolete. The team had to choose between Siemens 3RT2016-1AP01 and Eaton DILM9-10(230V50HZ), both offering a 9 A AC-3 rating well-matched to the motor FLA.

rice delta per unit was negligible (€2.40 in Siemens' favor). What tipped the decision was accessory inventory: the plant's maintenance stores already carried Eaton DILA auxiliary blocks for their downstream conveyor panels, and standardizing the retrofit on DILM9 meant a single aux block SKU across the whole plant.

Two years on, the plant reports zero unplanned contactor failures and sub-24-hour MTTR on the rare auxiliary block swap. The moral: brand choice on paper was a wash; operational standardization won the day. This is the kind of reasoning that doesn't show up in a datasheet comparison.

Mounting, wiring, and panel ergonomics

Both families mount on 35 mm DIN rail up to approximately 80 A AC-3 frames. Above that, you're into screw-mount on backplate territory. Siemens 3RT2 frames S6 and up use M6 mounting studs. Eaton DILM150 and above use M6 or M8 depending on frame.

Terminal types and wiring discipline

Siemens 3RT2 offers screw terminals (standard), spring-loaded terminals (the "-3" variant, e.g., 3RT2026-2BB40), and ring-lug terminals on larger frames. Eaton DILM offers screw and SmartWire-DT options. The SmartWire-DT system is Eaton's proprietary bus that eliminates individual control wiring — a genuine differentiator if you're building standardized panels in high volume.

For one-off or low-volume builds, SmartWire-DT is overkill. For an OEM building 200 identical pump panels a year, it cuts wiring time by roughly 40% based on customer reports we've heard. Not a universal win, but worth evaluating for high-repeat production.

Box lugs and cable prep

A common mistake: assuming box lugs accept the same cable range across brands. Siemens 3RT2046 accepts 16–70 mm² solid or stranded. Eaton DILM95 accepts 25–70 mm². On copper lug terminations with cable-shoe ferrules, the practical range narrows further. Always cross-check the manufacturer's terminal capacity table before committing to a cable size.

Environmental ratings and special applications

Both 3RT2 and DILM carry IP20 terminal protection as standard. For marine, offshore, and aggressive atmospheres, both manufacturers offer conformal-coated variants. Siemens designates these with "-TS" suffix; Eaton uses "-TK" or similar regional coding.

Ambient temperature ratings per IEC 60947-4-1 §7.2.1.1: both families are rated -25 °C to +60 °C storage and -5 °C to +55 °C operation at full AC-3 current. Derating applies above 55 °C. In desert installations we've worked on (Kuwait, Saudi Arabia), panel internal ambient routinely hits 65 °C in summer even with ventilation, so derating is non-optional.

For altitude derating: above 2000 m, both manufacturers require current and voltage derating. Typical correction is 0.95 × Ie at 3000 m, 0.80 × Ue at 3000 m per IEC 60664-1. For high-altitude installations in the Andes or Himalayas, always request a derating confirmation from the manufacturer's technical support.

Obsolescence, availability, and long-term spare parts strategy

Siemens 3RT2 replaced the older 3RT1 series around 2013. 3RT1 parts are still available through some channels but are officially end-of-life. If you're maintaining a plant with 3RT1 contactors, you can cross-reference to 3RT2 — the mounting footprint and auxiliary block interface are compatible for most frames.

Eaton DILM replaced the older Moeller DILR series in the mid-2000s. DILR parts are essentially extinct now; retrofits to DILM require minor panel modifications because the mounting footprint shifted slightly on frames above DILM25.

For long-term spare parts strategy, keep one contactor of each frame size on hand per MCC — plus one matching auxiliary block and one surge suppressor. That's typically 6–10 SKUs per plant for complete coverage of frames from 9 A to 95 A. Both manufacturers commit to 10+ year parts availability on current generation products, though we've seen Eaton honor spare requests on 15+ year old Moeller DILM variants through their German service organization.

Conclusion: how to choose between Siemens 3RT and Eaton DILM

After two decades of panel builds across multiple continents, here's our honest take: Siemens 3RT2 and Eaton DILM are technically equivalent for 90% of industrial AC-3 motor starting applications. Both meet IEC 60947-4-1 requirements, both offer Type 2 coordination to 100 kA with matched upstream devices, both have mature accessory ecosystems and reliable long-term parts support.

The decision should hinge on three practical factors. First, regional distributor stock depth — whichever brand your three primary suppliers stock in real quantity wins the lead-time war. Second, existing plant standardization — if maintenance already carries one family's auxiliary blocks and surge suppressors, stay in that ecosystem. Third, application specifics — if you need wide-range electronic coils across every frame and don't want to pay for upgrades, ABB AF is worth considering alongside the two; if you need pre-assembled reversers, Siemens 3RA2 is class-leading; if you build repetitive OEM panels at volume, Eaton SmartWire-DT saves real wiring hours.

Price parity is close enough that €5–10 per contactor should not drive the decision. Total cost of ownership — which includes inventory complexity, training, documentation, and spare parts — matters ten times more than unit cost on a panel that will operate for 20 years. Make the boring, durable choice. It usually pays back within the first year of operation.

For engineers specifying installation contactors for lighting, HVAC, and resistive loads rather than motor starting, the ABB ESB family offers a parallel selection path with similar decision logic: size correctly to the load category, verify coil voltage and control interface, and standardize accessories across the plant. The principles are identical; only the utilization category changes.