We take cryptocurrency — so the coins you hold can buy real hardware.Pay in crypto, spend it on real hardware. Free insured shipping worldwide over $399. Plain, unbranded boxes, sent from Germany.Free insured shipping over $399. Your rate is locked for 30 minutes once checkout opens.Rate locked 30 minutes. Every item sealed, serial-checked and covered by a 24-month warranty.Sealed, 24-month warranty.

Saved items Sign in
Square D N250MJ panelboard main breaker kit, 250A 347V AC, with mounting hardware

SQUARE D

SQUARE D N250MJ Panelboard Main Breaker Kit 250A 347V AC

SKU CH-RFVJ-4M3HK

Complete 250 A main-breaker kit for three-phase 347 V AC J-frame panelboards, including cover plate, mounting hardware, brackets, rail extensions, splices.

  • 250 A three-phase main breaker kit for J-frame panelboards
  • 347 V AC rating suits commercial distribution systems
  • Includes cover plate, label, mounting plate, screws, brackets, rails, terminals and connectors
  • Frame size 225 A / J compatible with JDL, JGL, JJL, JLL and JRL series breakers
  • Compact 50 in × 20 in × 5.75 in enclosure footprint

Panelboard Main Breaker Kit 250A

The SQUARE D N250MJ kit provides a complete main breaker assembly for Square D J-Frame panelboards. It is intended for electricians and facility managers who need to install or replace a three-phase main disconnect rated at 250 amps. The package includes the cover plate, label, mounting plate, hardware, brackets, rail extensions, rail splices, terminals and connectors required for the installation. It ships in new condition.

347 V AC three-phase rating

The decisive specification is the 347 V AC three-phase voltage rating combined with a 250 A ampere rating. This kit is compatible only with Square D JDL, JGL, JJL, JLL and JRL series circuit breakers and a 225 A frame size. It will not fit panelboards built for other frame sizes or breaker series, and it cannot be used on systems operating at different voltages or phase configurations.

Sustained 250 A load capacity

Under continuous operation the kit supports its full 250 A rating within the 225 A frame size envelope. The included rail extensions, splices and brackets are designed to maintain secure mechanical and electrical connections during prolonged three-phase loading at 347 V AC. The assembly fits a 50 in by 20 in footprint with a 5.75 in depth, providing stable mounting for long-term service.

How it compares

Measured against everything we stock in Breakers & Circuit Protection, at today’s prices. Recalculated every night.

Price $503.99
Pricier than about 90% of the 1,135 comparable items (median $54.99).

Specifications

Product
Brand nameSQUARE D

Questions about this item

How does the 250 A rating work once the kit is installed in a panelboard?

The kit provides a main breaker rated at 250 A, 347 V AC, three-phase, and fits Square D J-frame panelboards with a 225 A frame size.

What does the 347 V AC rating limit in actual use?

It limits the maximum system voltage to 347 V AC three-phase, so the panelboard and all downstream circuits must operate at or below that voltage.

What physical space and mounting hardware does the kit need to fit?

The assembly measures 50 in long, 20 in wide and 5.75 in deep, and includes a cover plate, label, mounting plate, screw set, two support brackets, two rail extensions, two rail splices, two terminals and three connectors for installation.

More in Breakers & Circuit Protection

Similar items