Discontinued ABB Air Circuit Breaker (ACB)? Cross-Reference & Modern Replacement Guide If you're maintaining an older switchboard or motor control center in the UK, there's a good chance the original air circuit breaker (ACB) fitted to it is no longer in production. ABB's older SACE Emax range has been superseded by the Emax2 platform, and plenty of sites are still running the legacy frame long after the manufacturer moved on. This guide covers why that happens, what the modern equivalent looks like, and what to check before you swap one in. Working from an old ACB nameplate and need a modern equivalent? Request a Cross-Reference Quote Why the Original ACB Is Obsolete Manufacturers periodically retire circuit breaker platforms as electronics, communication protocols and testing standards move on. ABB's original SACE Emax range is a good example — it's been replaced across the board by Emax2, which carries updated Ekip electronic trip units (Ekip Dip, Ekip Touch, Ekip Hi-Touch) with better metering, communication and protection functions than the frames they replace. If your switchboard still has the older frame fitted, replacement parts and trip units for it become harder to source every year the platform stays out of production. Compatible Modern Equivalents Emax2 breakers are specified by frame size (E1.2, E2.2, E4.2, E6.2) and current rating, not by directly swapping an old part number for a new one — the frame needs to match your switchboard's physical mounting and busbar spacing. In practice, that means matching: Rated current (In) — matched to the incomer or feeder it protects. Frame size — physical envelope and connection centres compatible with the existing cubicle. Breaking capacity (Icu) — equal to or greater than the original, checked against current prospective fault levels. Trip unit type — Ekip Dip (basic LI/LSI) up to Ekip Hi-Touch (full metering and communication) depending on what the panel needs. Quick Tip Send us a photo of the existing breaker's nameplate rather than trying to read the part number over the phone — the frame size and Ekip release type are usually the two details that get misread. Cross-Reference Checklist Photograph the full nameplate — frame type, rated current, rated voltage and release type. Measure the cubicle's mounting centres and busbar spacing before ordering a replacement frame. Check the current prospective fault level at the board against the new breaker's Icu. Confirm whether a manual or motorised (withdrawable) racking mechanism is needed. Migration Considerations Beyond the breaker itself, an upgrade to Emax2 often changes the panel builder's job in three ways: the withdrawable truck and cassette may need to be swapped alongside the breaker (older Emax trucks aren't interchangeable with Emax2), the Ekip trip unit setup needs commissioning against the site's protection settings, and if the switchboard also has an upstream MCCB or thermal overload relay on downstream circuits, it's worth reviewing those settings together for correct discrimination. Most Common Mistake Ordering a replacement breaker on current rating alone and assuming the old withdrawable truck will still fit. Frame generations are rarely truck-interchangeable — check this before the breaker arrives on site. Brands We Supply Brand What We Stock Brand Page ABB Full Emax2 ACB range plus switch disconnectors for the same board View ABB → Related Categories Category What's Inside Category Page Switch Disconnectors 223 disconnectors for isolating boards ahead of maintenance View Category → Molded Case Circuit Breakers 249 MCCBs for lower current ranges than an ACB View Category → Busbars Distribution busbar systems for the same switchboard View Category → Frequently Asked Questions How do I identify my existing ACB's specification? Photograph the full nameplate, including frame type, rated current, rated voltage, breaking capacity and trip unit type — send this to our team for a like-for-like cross-reference. Is the withdrawable truck reusable when upgrading? Usually not — frame generations are rarely truck-interchangeable, so check compatibility before ordering rather than after the breaker arrives. Can ZF Corporation source genuinely obsolete ACB parts? Where an exact discontinued part is still obtainable we can source it, but in most cases a modern Emax2 equivalent is the more reliable long-term option. Does upgrading the ACB affect protection discrimination with downstream breakers? It can — any time the upstream ACB's trip settings change, it's worth reviewing discrimination with downstream MCCBs and MCBs on the same board. What is the typical lead time for an Emax2 replacement? Common frame sizes are typically available from stock; larger or less common configurations may carry a short lead time — send your nameplate details for an accurate quote. Conclusion A discontinued ACB doesn't mean an unprotected switchboard — it means matching the current rating, frame size, breaking capacity and tr…