ABB SACE Emax 2 in Data Center Main Distribution Boards: Design Guide

What is an ABB SACE Emax 2 main distribution board? An ABB SACE Emax 2 main distribution board is a low-voltage air circuit breaker assembly rated 400–6300 A at up to 1000 V AC under IEC 60947-2, with breaking capacities reaching 150 kA Icu, configured as the incomer protection layer in data center main switchgear. Undersizing the incomer relative to transformer fault contribution, mismatching selectivity settings across cascaded breakers, or selecting an inadequate Ekip trip unit can compromise Tier III/IV uptime requirements and violate coordination margins under IEC 60909. This guide covers transformer-to-breaker sizing logic, prospective short-circuit current calculation, full selectivity strategies for Tier III and IV topologies, Ekip Dip versus Ekip Touch versus Ekip Hi-Touch trip unit selection, and DCIM communication architecture integration.

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

Why the Emax 2 Dominates Data Center Main Distribution

Walk into any hyperscale or colocation facility built in the last decade and you'll see the same pattern at the MDB: an incoming ACB from the transformer secondary, a tie breaker, and outgoing feeders to PDUs, mechanical loads and UPS inputs. The reason the ABB Emax 2 has captured a significant share of these designs comes down to three things engineers care about: selectivity, diagnostics and footprint.

In our experience commissioning MDBs across EMEA and Southeast Asia, the Emax 2's Ekip Dip and Ekip Touch trip units provide the granularity needed to coordinate with downstream Tmax XT MCCBs without resorting to the brute-force time delays that erode let-through energy budgets. The frame is also compact: an E2.2 at 2000 A occupies the same panel width as an older E2 at 1600 A, which matters when you're trying to fit redundant 2N feeds into a 1200 mm switchgear column.

Why Not Just Use MCCBs?

A common question from procurement teams comparing capex: "Can't we use a 1600 A MCCB instead of an ACB at the incomer?" Technically, yes — frames like the Tmax XT7 reach 1600 A. But you lose three things. First, the short-time withstand current (Icw) of an ACB is typically 42–85 kA for 1 second, versus around 20 kA for 0.25 s on an MCCB; that one-second rating is what makes upstream-downstream selectivity possible during a real fault. Second, ACBs offer drawout construction, allowing maintenance without de-energizing the busbar. Third, the metering accuracy of Ekip trip units (Class 1 per IEC 61557-12) means you can decommission separate power meters.

Detailed performance class ratings, Icw values, and Ekip trip unit configurations for the ABB Emax 2 family are documented in the manufacturer's official ABB SACE Emax 2 product portfolio.

Sizing the Incomer: Transformer-to-Breaker Logic

The starting point for any ABB Emax 2 specification is always the transformer. A 2000 kVA dry-type transformer at 400 V secondary delivers a full-load current that engineers often miscalculate by ignoring the √3 factor or forgetting the continuous-load derating per NEC 215.2 (which doesn't apply directly under IEC, but the design philosophy of 80% continuous loading is widely adopted globally).

For a 2000 kVA / 400 V transformer: I_FL = 2,000,000 / (1.732 × 400) ≈ 2887 A. The natural breaker selection is an E2.2B 3200 A — but in data center practice, where transformer loading rarely exceeds 75% of nameplate (to preserve N+1 capacity headroom), engineers often specify a 2500 A or 2000 A frame. The ABB 1SDA071021R1 E2.2B 2000 A is a frequent choice for 1500 kVA transformers feeding mechanical MDBs.

Frame Selection Across E1.2 and E2.2

For sub-distribution boards within the data center — say, a mechanical chiller MDB rated 1000 A — the E1.2 frame is usually correct. The ABB 1SDA070781R1 E1.2B 1000 with Ekip Dip LI is a reasonable default for non-selective downstream feeders, while the LSI variant (such as the ABB 1SDA070782R1 E1.2B 1000 LSI) adds the short-time delay function essential for time-graded selectivity. For larger feeders to UPS systems, the ABB 1SDA070861R1 E1.2B 1600 handles 1600 A within the same E1.2 envelope.

Engineers often overlook that the "B" performance class (42 kA at 415 V) is sufficient for most data centers fed from 2000–2500 kVA transformers with typical 6% impedance. Specifying "N" or "S" class (65–85 kA) when not needed adds 15–25% to the unit cost and increases panel depth requirements. For a deeper dive into ratings, the Emax 2 full technical specifications guide walks through Icu, Ics and Icw across all frames.

Calculating Prospective Short-Circuit Current

Before you can finalize the breaking capacity of an ABB Emax 2 incomer, you need the prospective short-circuit current at the MDB busbar. This is non-negotiable per IEC 60947-2 §4.3.6.4 and is the single most common omission we see in third-party submittals.

For a 2000 kVA / 400 V / 6% impedance transformer, the calculator returns roughly 48 kA at the secondary terminals. After cable impedance from transformer to MDB (typical 5–10 m run), the value at the busbar usually drops to 38–42 kA — comfortably within the 42 kA rating of the Emax 2 "B" class. For sizing methodology details, see how to size ABB Emax 2 circuit breakers.

Selectivity: The Tier III/IV Differentiator

Selectivity (also called discrimination) is what separates a well-designed data center from one that loses an entire pod when a single PDU faults. The principle, defined in IEC 60947-2 Annex A and fully supported by the ABB Emax 2 trip unit suite, is that only the breaker immediately upstream of the fault should trip — not the incomer.

Time-Current Coordination in Practice

In a typical data center MDB-to-PDU coordination scheme, you have three layers: Emax 2 incomer, Tmax XT feeder breaker, and PDU-level MCCB. The Ekip LSI trip unit provides four protection functions — L (long-time), S (short-time), I (instantaneous), and optionally G (ground fault).

The short-time function is the magic ingredient. By setting an intentional delay of 100–300 ms on the Emax 2's S function, you give the downstream Tmax XT enough time to clear a fault on its load side before the incomer reacts. A common mistake is leaving the I (instantaneous) function enabled at low pickup; this overrides the S delay and breaks selectivity. For incomers in selective schemes, set I = OFF or above the maximum prospective Isc at the busbar.

What we typically see in the field on retrofit projects is that older installations used MCCBs at the incomer with no Icw rating — meaning the moment fault current exceeds the instantaneous threshold, the breaker trips regardless of any downstream device. Replacing those incomers with Emax 2 frames like the ABB 1SDA070741R1 E1.2B 800 immediately restores time-graded selectivity.

Trip Unit Selection: Ekip Dip vs Ekip Touch vs Ekip Hi-Touch

Not all Ekip trip units fitted to the ABB Emax 2 are created equal, and the procurement decision often hinges on whether the data center DCIM (Data Center Infrastructure Management) platform requires real-time energy data.

For a Tier III colocation MDB, Ekip Touch is usually the sweet spot. The ABB 1SDA070701R1 E1.2B 630 with Ekip Dip LI works fine for non-critical sub-feeders, but I'd push back on specifying Dip-only for incomers where SCADA visibility matters. For a comparison against the main competitor, see ABB Emax 2 vs Schneider MasterPact MTZ.

Communication Architecture: Integrating with DCIM

Modern data centers expect every breaker above 400 A to expose at minimum: trip status, current per phase, voltage, kW, kWh, and trip cause history. The ABB Emax 2 with Ekip Com modules supports Modbus TCP, Profinet, EtherNet/IP, IEC 61850 and DNP3.

In our experience, the gotcha is the network topology. A common mistake is daisy-chaining 12+ breakers on a single Modbus RTU loop; you end up with polling cycles approaching 5 seconds, which fails most DCIM SLA requirements. Use Ekip Com Hub gateways to bridge to TCP/IP, with no more than 8 devices per RTU segment.

Cybersecurity Considerations

Since 2022, IEC 62443-4-2 compliance has become a procurement requirement for hyperscale operators. Emax 2 trip units released after firmware version SW 2.50 support encrypted communication and role-based access; older firmware does not, and that's a legitimate reason to reject offered stock from gray-market sources. Always verify firmware version on delivery.

Common Field Problems and How to Avoid Them

Three issues account for roughly 80% of the support tickets we field on ABB Emax 2 installations.

Nuisance Tripping on UPS Bypass

When a static UPS transfers to bypass, the inrush into the bypass static switch can briefly exceed 8× nominal. If the Emax 2 feeding the UPS bypass has its instantaneous (I) function set at 6× In, you get nuisance trips during what should be a routine transfer. Solution: raise I to 10–12× In or disable I entirely on bypass feeders, relying on S protection. We covered the diagnostic process in detail in Emax 2 nuisance tripping root causes.

Harmonics and Thermal Derating

Data center loads are notoriously harmonic-rich. Server PSUs at low load can push THDi above 30%, and chiller VFDs add 5th and 7th harmonic content. Per IEC 60947-2 §8.3.3.5, true-RMS sensing is required for accuracy under these conditions — fortunately, all Ekip trip units are true-RMS by design. But the breaker itself may need derating: at 50 Hz with THDi > 25%, apply a 0.95 factor to the rated current.

Drawout Mechanism Maintenance

Engineers often overlook that drawout Emax 2 units require lubrication of the racking mechanism every 2 years or 200 racking operations, whichever comes first. Skip this and you'll find yourself unable to rack a breaker in during a planned maintenance window — exactly when you need it most. For broader maintenance scheduling, refer to the section on preventive maintenance in our Emax 2 features and benefits overview.

Procurement Checklist for Emax 2 in Data Center MDBs

When issuing the ABB Emax 2 BoQ to suppliers, specify the following at minimum to avoid substitution surprises:

Frame and rating: Exact code (e.g., E2.2B 1600 with Ekip Touch LSI). Don't leave "or equivalent" language for critical incomers — the configuration permutations are too many. Performance class: B, N, S, H, V, X — must match your calculated Isc plus 25% margin. Trip unit firmware: Latest stable release; specify minimum SW version. Accessories: Auxiliary contacts (AUX), shunt trip (YO), undervoltage release (YU), motor operator (M), Ekip Com module type. Drawout vs fixed: Drawout (W) for incomers and tie breakers; fixed (F) acceptable for downstream feeders. Country of origin: Verify factory; ABB produces Emax 2 in Italy (Bergamo), with regional assembly in some markets. Gray-market substitutions from secondary channels often fail FAT.

For sister applications outside data centers — like offshore platforms with their own selection logic — see Emax 2 in oil and gas offshore platforms. Browse the full Air Circuit Breakers collection at Stoklink, alongside complementary MCBs, RCDs and protection relays.

Conclusion

Specifying the ABB SACE Emax 2 for a data center main distribution board is rarely about the breaker alone — it's about the entire coordination scheme, communication architecture, and lifecycle support model that surrounds it. Get the frame size right based on actual continuous load (not nameplate kVA), choose a performance class that matches your calculated short-circuit current with sensible margin, and invest in Ekip Touch or Hi-Touch trip units where DCIM integration matters. Build selectivity into the design from day one using the Icw rating and short-time delay function, and don't compromise on firmware version or accessory specification when negotiating with suppliers.

The breakers themselves — frames like the ABB 1SDA070821R1 E1.2B 1250 for mid-range feeders or the ABB 1SDA070981R1 E2.2B 1600 for higher-current applications — are proven assets when applied correctly. The Emax 2 platform has earned its position in critical power infrastructure precisely because it gives engineers the tools to engineer reliability, rather than hope for it. For the complete selection methodology including coordination tables, accessory matrices and full maintenance schedules, see our ABB SACE Emax 2 Selection, Application and Maintenance Guide.