Resources for People Working on Real Panels
Cross-reference charts, sizing tables, nameplate decoders and enclosure ratings — written by the counter staff who answer these questions on the phone all day. No gated PDFs and no lead-capture wall.
Start With What You're Trying to Do
Identify a part I can't look up
Nameplate decoding and legacy-to-current cross-reference charts for discontinued frames.
Cross-reference guides →Size or specify the right part
NEMA starter sizing, fuse classes, transformer kVA and enclosure ratings.
Sizing guides →Satisfy an inspector
What the standards require of reconditioned gear, and the documentation to have ready.
Code & compliance →Diagnose something failing
Tripping breakers, chattering starters, welded contacts — what the symptom actually indicates.
Troubleshooting →All Guides
18 guidesTime-Delay vs Fast-Acting Fuses: What to Verify Before Replacing One
A time-delay fuse and a fast-acting fuse can share the same voltage, ampere rating, and even the same UL fuse class while providing different protection behavior. That means one should not be substitu...
Read the guide →Class J, RK1, RK5 and CC Fuses: What Changes When You Replace One?
Class J, RK1, RK5 and CC are not simply four labels for the same kind of fuse. Each class has its own dimensional, rejection, voltage, and performance rules, and even two fuses within the same UL clas...
Read the guide →Mersen and Ferraz Shawmut Fuse Cross-Reference Checklist
Older industrial equipment may contain fuses labeled Shawmut, Gould Shawmut, or Ferraz Shawmut, while current replacement research is typically performed through Mersen. The brand history is useful fo...
Read the guide →Bussmann Fuse Cross-Reference: What to Check Before Ordering
A Bussmann cross-reference should be treated as a qualified starting point, not as final proof that one fuse can replace another in every application. Eaton's Bussmann FuseFinder is designed to identi...
Read the guide →Industrial Fuse Cross-Reference: A Verification Workflow
An industrial fuse cross-reference should be treated as a starting point for technical verification, not as automatic approval to substitute one part for another. The same ampere rating does not prove...
Read the guide →Square D I-Line Breaker Replacement: What to Verify Before Ordering
A Square D I-Line breaker replacement should be identified from the full catalog number, breaker frame, electrical ratings, mounting arrangement, phase connection, suffixes, and parent panelboard. Phy...
Read the guide →Crouse-Hinds Breaker Replacement: What to Verify Before Ordering
A legacy Crouse-Hinds breaker should not be replaced by brand name, amperage, or physical appearance alone. Start by identifying the exact breaker type, catalog number, electrical ratings, mounting ar...
Read the guide →Siemens Molded-Case Breaker Catalog Numbers: What Buyers Need to Verify
A Siemens molded-case circuit breaker catalog number is more than an inventory identifier. Depending on the breaker family, it can communicate frame size, voltage class, pole count, interrupting range...
Read the guide →Obsolete Electrical Parts Sourcing Guide: How to Find Discontinued Industrial Components
When a critical electrical component fails, the fastest path to a replacement usually starts before anyone searches inventory. The first job is to identify exactly what is installed, document the rati...
Read the guide →ITE Industrial Breaker Replacement: What to Verify Before Ordering
Replacing an obsolete ITE industrial circuit breaker starts with identification, not with a visual match. Two breakers can look nearly identical and still differ in frame, interrupting rating, trip fu...
Read the guide →Why Similar-Looking Circuit Breakers May Not Be Interchangeable
Two circuit breakers can have the same amperage, similar case dimensions, the same number of poles, and even appear to fit the same opening without being interchangeable. A correct replacement must be...
Read the guide →New vs. Reconditioned vs. Surplus vs. Used Circuit Breakers: Industrial Buyer’s Guide
By the JW Electrical Supply team — electrical distribution specialists since 1977.
Read the guide →Electrical Cross-Reference Guides & Sizing Charts
This library exists because the same questions arrive at our counter every week: what replaces a discontinued Westinghouse frame, which NEMA starter size fits a 25-horsepower motor, whether a Class RK5 fuse can drop into a Class J holder, and what the numbers on a forty-year-old nameplate actually mean. Rather than answer each one on the phone, the counter staff wrote them down.
Everything here is free and ungated. The cross-reference charts cover legacy Square D, Westinghouse, Federal Pacific, Challenger, ITE/Gould and Wadsworth frames; the sizing material covers NEMA and IEC starters, fuse classes, transformer kVA, and NEMA enclosure ratings for outdoor and washdown environments.
One caution worth stating plainly: a chart narrows the field, it does not clear an install. Interrupting rating, frame dimensions, mounting method and terminal type all have to be confirmed against the equipment in front of you, and your AHJ has final say. When the stakes are a live panel, call +1 410-817-2216 and read us the nameplate — that check is free.
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