Schneider Electric · Micrologic
Masterpact NW & NT Repair and Refurbishment
The NW and NT replaced the Masterpact M. They are still widely installed, and the oldest are now past twenty years in service. We strip them, rebuild the mechanism, replace coils, motors and contacts, test the Micrologic trip unit by secondary injection and fly them back to your site.
- FramesNT06–NT16 · NW08–NW63
- Trip unitsMicrologic A · P · H
- Turnaround2–5 workshop days
- Warranty24 months on overhauls
Repair, don't replace
Keep the breaker that fits the cell
Masterpact NW and NT are current-generation in the sense that Schneider still supports them, but the newest range is MTZ. When an older NW starts to fail, the conversation can drift toward replacement or an upgrade that changes the cradle, the wiring and the settings.
Most NW and NT faults don't need any of that. A slow-closing mechanism, a dead MCH gear motor, a failed XF closing coil or worn contacts are bench repairs. Where genuine Schneider parts exist, we fit them. The rebuilt breaker goes back into the cradle it came out of, with the same secondary wiring and the same protection settings, and the switchboard is never touched.
That matters more in the US, where Masterpact turns up in European-designed distribution in data centers and in plant that arrived with its own switchboard. A repair keeps that equipment exactly as it was designed and approved. A new breaker on a long lead time keeps the cell empty.
- No board or cradle modification
- Protection settings restored as left, and proven by test
- Fixed price after strip-down
Common faults
What we see on NW and NT breakers
Slow or failed closing
On any Masterpact past ten years old, hardened mechanism grease is the first suspect. Check the MCH has charged and the XF coil has supply, then look at the mechanism.
Won't charge
MCH gear motor failure, its limit switch, or the charging handle linkage. The motor is replaced and the charge time checked.
Coils and releases
XF closing coils, MX shunt trips and MN undervoltage releases fail with age and heat. Each is tested and replaced, and proven at reduced voltage.
Contact wear
Main and arcing contacts erode on high-operation duty, where the breaker is switched often.
Micrologic faults
Drift, battery and connector faults. Secondary injection tells us whether the trip unit is at fault or the problem is downstream.
Cradle and secondaries
Eroded or overheated cluster contacts, worn racking mechanisms, position switch faults and damaged secondary disconnect blocks.
The refurbishment
What a full NW or NT overhaul includes
- Strip-down to the frame; wear measured against OEM limits before we quote
- Mechanism dismantled, cleaned, worn parts replaced, re-lubricated, travel and latching verified
- Main and arcing contact sets renewed; arc chutes cleaned and inspected
- MCH gear motor and XF, MX and MN coils tested and replaced as needed
- Auxiliary contacts and secondary disconnect blocks restored
- Micrologic trip unit tested, repaired or replaced, and set to your protection settings
- Trip unit upgrades on request, for example Micrologic A to P or H for metering and communications
How it is tested
Secondary injection on long-time, short-time, instantaneous and ground-fault elements as fitted, each result printed beside its tolerance band. Contact resistance per pole, insulation resistance, and mechanical operation. The certificate records the as-left settings against the serial number.
Coverage
Masterpact NW and NT models we repair
| Range | What we cover |
|---|---|
| Masterpact NT | NT06 to NT16, fixed and drawout. Mechanism, MCH motor, XF coil, MN release, auxiliary blocks. |
| Masterpact NW | NW08 to NW63, fixed and drawout. Mechanism, MCH motor, coils, main contacts, secondary disconnects, Micrologic. |
| Trip units | Micrologic A, P and H: test, repair, replacement and upgrade |
| Cradles | Cluster contacts, racking mechanism, position switches |
| IEC and UL versions | IEC-frame units and UL-listed versions, including Square D-branded Masterpact. A repair restores the breaker to its original design; we don't re-certify a UL listing. |
| Other generations | Masterpact M (obsolete) and MTZ, the current range |
We repair both: the IEC Masterpact NW and NT found in European-built equipment, and the UL-listed Square D versions installed in US switchgear.
From your site and back
Turnaround, Express and exchange
Standard
Air freight takes about 3 days each way. Workshop time is 2–5 working days depending on severity, so most units are back in about 8–11 working days, plus customs clearance.
How it worksExpress
1–2 days in the workshop. About 7–8 working days door to door, plus clearance.
Exchange units
We hold many tested units in the UK*, flown out the day you report a fault if your model is in stock.
Exchange unitsCustoms
DAP or DDP, your choice. We prepare the commercial invoice and the repair-and-return paperwork.
Shipping & customs*Subject to model and rating.
FAQ
Masterpact NW and NT questions
Do you repair Square D Masterpact breakers?
Yes. Square D-branded Masterpact NW and NT units are part of the same family. We repair the breaker to its original design and test it; we don't issue or renew a UL listing.
Do you use genuine Schneider parts?
Where they exist, yes. MCH motors, XF, MX and MN coils, Micrologic units and contact sets for NW and NT are Schneider parts. The certificate lists what was fitted.
Can the breaker be repaired without leaving our site?
Drawout units come out of the cradle and travel to the workshop, where the bench, the test set and the parts are. If you have many units, our engineers can travel to the US and do the work on site. On-site in the US.
Our Micrologic shows a fault but the breaker seems fine. What should we send?
Send the breaker. Injection testing on the bench shows whether the trip unit has drifted or failed, or whether the fault is in the wiring or downstream. You get the answer on the certificate.
Will it come back with our settings?
Yes. Send the settings from your drawings or a photo of the trip unit. The breaker is set to them, tested at them, and the as-left settings are recorded.
Send us the nameplate
A photo of the nameplate and the fault is enough for a first answer. We reply the same working day with a recommendation and a price for diagnosis and freight.