How to Read an MPCB and Contactor Coordination Table

How do you read an MPCB-contactor coordination table? A coordination table published under IEC 60947-4-1 lists, for each MPCB rated current, the exact contactor and overload relay it was tested with, the prospective short-circuit current (Icc) the combination was verified at, and whether the result was declared Type 1 or Type 2. Pick a combination outside that table — swap in a different contactor frame, exceed the tested Icc, or ignore the declared Type — and the tested coordination no longer applies, so a fault beyond the panel's design current can damage more than the manufacturer intended. This article covers the row structure, the Type 1/Type 2 column, matching rated currents, checking Icc against your installation, cross-checking the contactor and relay columns, and the mistakes that void a table's validity.

What an MPCB-Contactor Coordination Table Shows

Every MPCB manufacturer tests specific combinations of MPCB, contactor, and (where used) overload relay together in a lab, at a declared prospective short-circuit current, and publishes the results as a coordination table. The table is not a suggestion — it is the tested evidence that lets a panel builder claim compliance with IEC 60947-4-1 clause 8.2.5 without running the short-circuit test itself.

A typical row lists the MPCB type and rated current setting range, the contactor reference and its rated operational current (Ie), the overload relay reference if the MPCB is magnetic-only, the Icc value the combination was tested at, and the coordination Type achieved at that Icc. Read left to right, each row is one certified combination — not a menu where columns mix and match freely.

Type 1 vs Type 2: The Column That Decides Everything

Type 1 coordination means that after a short circuit, the MPCB and contactor may be damaged and require replacement — the fault must not endanger the operator, but the starter itself is not guaranteed serviceable. Type 2 coordination means no damage beyond light contact welding on the contactor, separable without tools, and the starter is back in service after the fault clears.

Type 2 costs more to achieve — it usually forces a lower fault-current rating for the same components, or a larger MPCB paired with the same contactor. Panels built for continuous-process lines, where an unplanned starter replacement means downtime, specify Type 2. Panels where first cost matters more than a five-minute component swap often accept Type 1. See our dedicated breakdown of MPCB Type 1 vs Type 2 coordination for the damage-tolerance details behind each declaration.

Matching the MPCB Rated Current to the Correct Table Row

The MPCB's setting range must bracket the motor's full-load current (FLC), and the table row used must match the MPCB's rated current and dial setting — not just any row with a similar contactor. A 16 A frame set at 6 A and the same frame set at 14 A can carry different Icc ratings in the same table, because the tested fault current depends on the actual setting, not the frame alone.

Cross-reference the FLC from the motor nameplate against the MPCB's dial range first, confirm the setting sits inside that range, then find the table row for that specific rated current and setting combination. Skip a step and the coordination relied on was never tested at the operating point in use.

This is where manual motor starters from different manufacturers diverge in table structure — some group several settings under one row, others publish a row per discrete setting point. Check which format a given manufacturer uses before assuming a row applies to an exact dial position.

Reading the Icc (Short-Circuit Current) Column

Icc in the table is the prospective short-circuit current the combination was tested against, at a stated voltage (commonly 400 V or 415 V) — not the MPCB's own interrupting rating in isolation. A 65 A frame MPCB might carry a 100 kA Icu rating on its own datasheet page but only 50 kA Type 2 coordination with a specific contactor, because the contactor's let-through energy is the limiting factor, not the MPCB.

Compare the table's Icc value against the prospective fault current at the point of installation, obtained from a short-circuit study or the transformer/utility impedance data. If the fault current at that panel exceeds the table's Icc, the combination is unverified at that site, even if every individual component's own rating looks sufficient on its own datasheet.

What we see in the field: builders sometimes read the MPCB's own Icu off its datasheet and assume that figure applies to the whole starter. It doesn't — the table's Icc is almost always lower, because it reflects the weakest component in the tested pair, not the strongest.

Cross-Checking the Contactor and Overload Relay Columns

For a thermal-magnetic MPCB, the table's contactor column is the only variable, since the MPCB itself provides overload protection and no separate relay row exists. For a magnetic-only MPCB, the table adds a third column: the overload relay reference, because thermal protection now lives in that separate device.

Builders using magnetic-only MPCBs sometimes size the overload relay from a generic FLC chart instead of the table's specific relay reference. The relay's trip characteristic and the magnetic-only MPCB's fixed trip point were coordinated as a pair in testing — swapping the relay brand breaks that pairing even when the new relay's current range looks compatible on paper.

Building the full starter around the exact references in one table row is the fastest way to keep the declared Type intact. See building an MPCB and contactor motor starter for the assembly side, and pair a magnetic-only MPCB with thermal overload relays only from the table's listed reference, not a generic sizing chart.

Common Mistakes When Reading Coordination Tables

Four mistakes account for most miscoordinated starters found in field audits. Reading the MPCB's standalone Icu instead of the table's tested Icc for the combination. Substituting a contactor from a different range because it shares the same Ie, without checking it appears in the same row. Using a Type 1 row when the specification calls for Type 2, because the Type 1 row often shows a higher Icc and looks like the stronger number at a glance. Ignoring the dial-setting column and applying a row validated at a different setting point to a motor with a different FLC.

This depends on how the original short-circuit study was scoped, too — a table read as valid against an older fault-current calculation may not reflect a since-expanded transformer or an added parallel feeder. Set it wrong and the coordination documented on paper does not exist on the panel.

How Coordination Table Format Differs by Brand

Schneider, ABB, and Siemens all publish tables that map MPCB, contactor, and Type to a declared Icc, but the layout and lookup method differ enough to slow down a first read.

The lookup logic stays the same across all three: find the MPCB rated current and dial setting, find the row, read the paired contactor (and relay, if magnetic-only), then read the Icc and Type for that exact row. When a project standardizes on one manufacturer's motor protection circuit breakers and contactors, staying inside that manufacturer's own table avoids cross-brand coordination questions the tables were never tested to answer.

Conclusion

A coordination table is read one row at a time: MPCB rated current and dial setting, paired contactor (and overload relay, if magnetic-only), declared Icc, and Type. Every substitution outside that row — a different contactor, a higher fault current, the wrong Type — needs a fresh manufacturer confirmation before it goes on the panel schedule. Start from the MPCB engineering guide for the broader selection process, and cross-check the standard itself against IEC 60947-4-1 standards for contactors and motor starters whenever a table's terminology needs clarifying.