Compact NSX <630 is discontinued — what replaces it, and how to specify the successor

If you maintain a switchboard built in South Africa between roughly 2008, when Compact NSX was launched, and 2020, there is a good chance a Compact NSX is sitting in it. It was Schneider Electric’s workhorse moulded-case breaker for well over a decade, and it is the range most often named in the spares enquiries we receive. It has been superseded by ComPacT NSX — the new generation — and the substitution is usually straightforward. Usually. The cases where it is not are the reason this guide exists.

What actually changed, and what did not

The first thing to understand is that this is a generational refresh of a range that Schneider intends to keep selling, not a withdrawal. That distinction matters commercially: you are not being pushed onto a different product family with a different footprint and a different accessory set. The frame sizes, the current ratings and the breaking-capacity classes continue. The naming convention continues. Much of what is bolted onto the breaker continues.

What changes is the electronics and the supporting ecosystem — trip unit generations, communication options, and the connected-product features Schneider has been building across its low-voltage portfolio. For a breaker doing nothing more than protecting a feeder with a thermal-magnetic trip, that change is close to invisible. For a breaker with a Micrologic electronic trip unit feeding data into a power-monitoring system, it is the whole question.

So the practical rule when replacing a Compact NSX is: the more the original breaker was doing beyond opening on a fault, the more carefully the replacement has to be specified.

The four things to check before you order

1. The trip unit, first and always

A moulded-case breaker’s order code identifies the frame and the breaking capacity; the trip unit is what determines whether it protects your circuit correctly. On the Compact NSX range that could be a thermal-magnetic unit — fixed or adjustable — or one of several generations of Micrologic electronic unit with long-time, short-time, instantaneous and, on some, earth-fault protection.

When you substitute, the replacement trip unit must be able to reproduce the settings the existing one is carrying. Not the settings the drawing specifies — the settings actually on the dial or in the unit today, because on an installation that has been modified over fifteen years those two are frequently different. Photograph the trip unit’s front face before the breaker comes out. It is the single most useful thing you can do for whoever specifies the replacement, and it takes ten seconds.

2. Whether the breaker is fixed, plug-in or drawout

A fixed breaker is a simple swap. A plug-in or drawout breaker sits on a base or in a cradle, and that base is part of the substitution question: if the base stays, the replacement must fit it; if the base is replaced, the switchboard work is no longer a ten-minute job and the outage needs planning accordingly.

This is the item most often missed in a spares enquiry, because the order code on the breaker’s own label does not always make the mounting arrangement obvious to someone reading it over the phone. If you can see a cradle, say so.

3. The accessories actually fitted

Auxiliary contacts, alarm contacts, shunt trips, undervoltage releases, motor mechanisms, rotary handles, door interlocks, terminal shields. Each of these has its own reference, and each has to be confirmed against the new generation rather than assumed. Most carry over. “Most” is not a basis for a shutdown plan.

Open the breaker’s accessory cover and list what is in it, or photograph it. On a panel with twenty breakers this is twenty minutes of work that removes the largest single source of return-to-site.

4. Whether anything downstream depends on the discrimination study

If the installation has a coordination or discrimination study, changing a breaker generation changes the curves it was based on. In many cases the new device’s characteristics are close enough that the study still holds, but “close enough” is a judgement for the person who signed the study, not for the person ordering the part. Where a study exists, flag the substitution to whoever owns it.

Reading the two order codes side by side

Both generations use a structured order code, and the structure is what lets you carry information from the old reference to the new one. Broadly, the code tells you the frame, the breaking-capacity class, the number of poles, the rating, and the trip-unit arrangement — with accessories carrying their own separate references.

The important discipline is to treat each block as a question to be answered rather than a string to be pattern-matched. Two references that differ by one character can differ by a breaking-capacity class, and breaking capacity is the parameter you cannot get wrong: a device with insufficient interrupting capacity at its installed point does not fail gracefully.

Why we do not publish a one-to-one substitution table

We could produce a table mapping every old reference to a new one, and it would be popular. We do not, for one reason: a substitution table that is right 95% of the time is more dangerous than no table at all, because the 5% is invisible until the breaker is on site and the switchboard is open.

Schneider maintains the authoritative substitution tool for this range and keeps it current as the new generation’s references evolve. That is the source we point to and the source we use ourselves. Where a substitution is genuinely one-to-one, our own product page for the discontinued reference names the replacement and links to it directly — and where it is not, the page says what has to be confirmed instead of guessing on your behalf.

How to check this on our site

Every discontinued reference in our catalogue carries an availability note on its product page naming the manufacturer’s stated successor, with the substitution guide linked. If you search a Compact NSX order code and land on a product page with that notice, the replacement named there is the manufacturer’s, not ours.

If you have a list rather than a single part — a panel schedule, a spares list, a maintenance BOM — paste it into our bulk quote tool rather than sending references one at a time. It matches what it can against the catalogue and tells you plainly which lines it could not match, which is exactly the list you want a person to look at.

What to send us if you want this quoted

The fastest possible enquiry on a Compact NSX replacement contains four things: the full order code from the breaker label, a photograph of the trip unit’s front face, a note of whether it is fixed, plug-in or drawout, and the quantity. With those four we can usually come back the same day. Without the trip unit photograph we will come back asking for it, which costs both of us a day.

Schneider Electric’s substitution guide

The manufacturer’s own reference-by-reference substitution guide for Compact NSX to ComPacT NSX: Compact NSX to ComPacT NSX substitution guide (Schneider Electric).

A closing note on responsibility

This guide is written to help you ask the right questions, not to answer them for your installation. The selection of a protective device is the responsibility of the person designing or maintaining the installation, and it depends on the prospective fault current, the coordination requirements and the standards the installation is built to. Where a substitution affects protection settings or a discrimination study, it should be reviewed by a competent person before the breaker is energised. We supply the equipment and the manufacturer’s documentation; we do not certify the design.