Switchgear, Molded-Case Circuit Breakers & UL Class Industrial Fuses — Lowell, MA
Direct counter sourcing and obsolete nameplate cross-referencing for 120/208V and 277/480V 3-phase panelboards, bolt-on and plug-in thermal-magnetic breakers, heavy-duty fusible safety switches, and current-limiting industrial fuses.
Engineering-Grade Overcurrent Protection for New England Mills, Campuses & Plants
When a main feeder fuse clears during a peak production shift or a 40-year-old bolt-on breaker trips in a school mechanical room, waiting days for a regional distribution center shipment is not an option. Furthermore, substituting a non-current-limiting fuse into a high-fault-current industrial service panel violates NEC 110.9 / 110.10 and NFPA 70E arc-flash boundaries.
Since 1927, Frank P. McCartin Co., Inc. at 149 Congress Street in Lowell has maintained one of northern Massachusetts's deepest counter inventories of commercial circuit breakers, heavy-duty NEMA 1/3R/4X/12 safety switches, and dual-element time-delay fuses. We stock and cross-reference active and legacy lines from Cutler-Hammer (Eaton), Square D, Siemens, Westinghouse, General Electric, Connecticut Electric (certified replacement breakers for obsolete panels), Bussmann, and Gould / Ferraz Shawmut (Mersen).
Need Immediate Part Verification?
Bring your sample component or email a clear nameplate photo to our 149 Congress Street counter team for same-day pickup or regional truck delivery.
UL Industrial Fuse Class & Interrupting Rating Cross-Reference Matrix
Counter cross-reference between Bussmann, Gould/Ferraz Shawmut (Mersen), and Littelfuse for motor branch circuits, control transformers, and service entrances.
| UL Fuse Class | Voltage & Amp Range | Interrupting Rating (IR) | Bussmann Series | Gould / Shawmut Series | Primary Industrial Application |
|---|---|---|---|---|---|
| Class RK1 (Time-Delay) | 250V / 600V • 1/10A–600A | 200kA RMS Sym. | LPN-RK (250V) / LPS-RK (600V) | A2D-R (250V) / A6D-R (600V) | Selective coordination, main feeders, critical MCC panels & high-fault switchgear |
| Class RK5 (Time-Delay) | 250V / 600V • 1/10A–600A | 200kA RMS Sym. | FRN-R (250V) / FRS-R (600V) | TR-R (250V) / TRS-R (600V) | 3-phase inductive motors, HVAC compressors & general heavy motor branch circuits |
| Class J (Dual-Element / Fast) | 600V • 1A–600A | 200kA RMS Sym. | LPJ (Time-Delay) / JKS (Fast) | AJT (Time-Delay) / A4J (Fast) | Compact Finger-Safe motor starters, VFD input protection & UL 508A control panels |
| Class CC (Rejection Midget) | 600V • 1/10A–30A | 200kA RMS Sym. | LP-CC / FNQ-R / KTK-R | ATDR / ATQR / ATMR | Control power transformers (CPT), solenoids, PLC power supplies & small 480V motors |
| Class T (Ultra-Fast Space-Saving) | 300V / 600V • 1A–1200A | 200kA RMS Sym. | JJN (300V) / JJS (600V) | A3T (300V) / A6T (600V) | High-density multi-family metering stacks, UPS inverter protection & non-inductive feeders |
| Class L (Bolted Blade) | 600V • 601A–6000A | 200kA RMS Sym. | KRP-C / KLU / KTU | A4BQ / A4BY / A4BT | Main service entrance switchboards, large chillers & bolted pressure contact switches |
Commercial & Legacy Circuit Breaker Frame Cross-Reference
Bring your pulled breaker or panelboard interior cat. number to 149 Congress St for physical bus-clip and AIC verification.
| Legacy / Active Panel Brand | Breaker Family / Mounting | Voltage & Poles | Current Replacement / Counter Solution |
|---|---|---|---|
| Cutler-Hammer / Westinghouse | Quicklag BAB (Bolt-On) / BA (Plug-In) /HBAX | 120/240V • 1P, 2P, 3P | Eaton BAB / QBHW (10kAIC–22kAIC) & Industrial Series C (FD, EHD, JD, KD) |
| Square D (Schneider Electric) | QO (Plug-In) / QOB (Bolt-On) / HDA / I-Line | 120/240V & 480Y/277V | Square D QO/QOB (Visi-Trip), EDB/EGB/EJB bolt-on & I-Line plug-on distribution breakers |
| Siemens / ITE / Gould | BL (Bolt-On) / BQD / QP / Cordon | 120/240V & 480Y/277V | Siemens BL / BQD bolt-on panelboard breakers & Sentron ED/FD/JD molded-case frames |
| Obsolete Pushmatic / Bulldog | Push-Button Bolt-On (P115–P2100) | 120/240V • 1P & 2P | Connecticut Electric UBIP newly manufactured ETL/UL listed Pushmatic replacement breakers |
| Obsolete Zinsco / Sylvania / FPE | Type Q / R38 / Stab-Lok NA & NC | 120/240V • 1P & 2P | Connecticut Electric UBIZ / UBIF newly tested replacement breakers or complete panel retrofit kits |
Counter Checklist: What to Bring When Replacing a Breaker or Fuse
- Full catalog stamping on the breaker handle or side label (e.g., BAB3050H, QOB360, EHD3040L) plus the panelboard interior series number.
- Mounting style verification: Bolt-on tab, plug-on jaw, or I-Line stack—plus physical pole width (3/4-inch vs. 1-inch per pole).
- Required interrupting rating (10kAIC, 22kAIC, 42kAIC, 65kAIC) and system voltage (240V delta vs. 480Y/277V vs. 600V).
- For fuses: Overall ferrule/blade length, diameter, rejection groove presence (Class R / Class CC), and whether the load is inductive (motor/transformer requiring dual-element time-delay) or resistive/electronic.
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Counter Q&A: Switchgear, Circuit Breakers & Industrial Fuses
Can I replace a Class RK1 fuse with a Class RK5 fuse in an existing disconnect switch?
While both Class RK1 and Class RK5 fuses fit the same rejection clips and share a 200kA interrupting rating, Class RK1 fuses (such as Bussmann LPN-RK/LPS-RK or Shawmut A2D-R/A6D-R) provide significantly lower peak let-through current (Ip) and I²t energy than Class RK5. You can safely upgrade from RK5 to RK1, but downgrading from RK1 to RK5 may compromise selective coordination or violate equipment short-circuit current ratings (SCCR).
Why do control power transformers in 480V motor starters require Class CC rejection fuses?
Primary windings of 480V-to-120V control power transformers experience magnetizing inrush currents of 25 to 40 times full-load amps for the first half-cycle. Dual-element time-delay Class CC fuses (such as Bussmann FNQ-R/LP-CC or Shawmut ATDR) hold through high magnetizing inrush while providing 200kA short-circuit protection required by NEC 430.72(C).
Do you stock replacement breakers for older Westinghouse and ITE panelboards in Lowell mills and schools?
Yes. Our Electrical Counter at 149 Congress Street stocks and cross-references Eaton Series C and Quicklag bolt-on breakers (direct replacements for legacy Westinghouse panels), Siemens BL/BQD breakers (for legacy ITE Imperial/Gould panels), and Connecticut Electric UL-listed replacements for obsolete Pushmatic, Zinsco, and Wadsworth loadcenters.
Request a Counter Quote or Cross-Reference: Switchgear, Circuit Breakers & Industrial Fuses
Routed directly to our 149 Congress Street, Lowell specialists. Eligible for COMMBUYS FAC124 (#201354) and MHEC G14 (#374) / G19 (#419) purchasing.