How to Find the Right Substitute for a Square D Bus Plug Using Cross Reference Techniques

To cross reference a Square D fusible bus plug, read the catalog number from the nameplate (for example PQ3603 or PQ4610G) and match it to a replacement with the same amperage, voltage, wire count and ground. BRAH Electric’s BPQ parts are listed as direct substitutes for Square D PQ fusible bus plugs on I-Line I and I-Line II busway, in 30A, 60A and 100A at 240V and 600V. The table below maps all 72 Square D numbers in the catalogue to the 24 BRAH parts that replace them.

Square D PQ to BRAH BPQ cross-reference table

Each row is one BRAH part and the Square D catalog numbers its record lists. Every part in the table is a 3-phase fusible plug, catalogue type PQ / BPQ, for the I-Line I & II busway family, and accepts Class H, R and J fuses. The part number links to its product page.

Three patterns hold across these 24 records and make the table quicker to read. Numbers starting PQ3 are listed as 3-wire and numbers starting PQ4 as 4-wire. A G after the digits is listed as “with ground”. The plain number and its R and J versions (PQ3603, PQ3603R, PQ3603J) share one BRAH part. Treat these as a reading aid for this table, not a rule for every Square D number, and confirm the ratings on the nameplate.

If your number is not in the table, type it into site search or browse the fusible bus plugs listing.

How to match a Square D bus plug step by step

The catalog number is the fastest route, but nameplates wear off and plugs get modified in the field. These seven checks use the same fields the BRAH catalogue stores for each part, so you can confirm a match even from a partial number.

1. Read the full catalog number

Copy the number exactly as printed, including any letters after the digits. PQ3610 and PQ4610G are different plugs: one is listed as 3-wire without ground and the other as 4-wire with ground. If the label is unreadable, check the panel schedule, single-line diagram or old purchase orders before you guess.

2. Match the amperage

The catalogue lists Square D fusible replacements at 30A, 60A and 100A. Order the same amperage as the plug you are removing. Each amperage is a separate part number, so the rating is chosen when you order, not adjusted afterwards.

3. Match the voltage

Each rating is listed in a 240V version and a 600V version, and they carry different catalog numbers (PQ3203 against PQ3603, for example). Pick the version that matches the old plug and is not lower than the system voltage. A 480V system needs the 600V part.

4. Count the wires and check for a ground

The catalogue records two things separately: wire count (3W or 4W) and ground (yes or no). A 4-wire plug carries a neutral. That gives four versions of each amperage and voltage: 3-wire, 3-wire with ground, 4-wire, and 4-wire with ground. Look inside the old plug for a neutral connection and a ground connection instead of relying on memory.

5. Confirm it is a fusible plug

Every BPQ part in the table is a fusible switch plug. Ground and neutral kits for Square D PFA and PKA breaker-type plugs are in the next section. A fusible plug and a breaker-type plug are not interchangeable without an engineering review of the protection. The guide to fusible and non-fusible bus plugs covers the difference.

6. Check the fuse class

All 24 parts are listed as accepting Class H, R and J fuses. Fuse class determines the physical size of the fuse and its interrupting rating, so the fuses you fit must suit the available fault current at that point in the system and the load being protected. Fuses are a separate purchase decision from the plug. See fuse classes in bus plugs for background.

7. Confirm the busway series

These parts are listed for Square D / Schneider Electric I-Line I and I-Line II busway only. A plug built for one busway family does not fit another, even at the same amperage and voltage, because the connection to the bus bars is specific to the busway design. Read the busway nameplate, not just the plug label, since plugs are sometimes moved between runs.

Ground and neutral kits for Square D I-Line bus plugs

If the plug body is sound and you only need to add or replace a ground or a neutral, the catalogue lists 11 kits for the I-Line I & II family. The neutral kits are described as kits for converting or adding a fourth-wire neutral to a three-phase plug. Mounting style matters here: several PQ neutral kits fit only the newer vertical mounting style, and others only the older horizontal style.

Browse the full bus plug ground kits and bus plug neutral kits listings for other busway families.

What to check before you order

• Catalog number: full number from the old plug, with suffix letters.
• Amperage: 30A, 60A or 100A, same as the plug being replaced.
• Voltage: 240V or 600V version.
• Wires and ground: 3W or 4W, with or without ground.
• Busway: Square D I-Line I or I-Line II, read from the busway nameplate.
• Fuses: class and ampere rating you will fit, checked against the available fault current.
• Mounting style: vertical or horizontal, if you are ordering a PQ neutral kit.

BRAH Electric is an aftermarket manufacturer and is not an authorized distributor of Square D or Schneider Electric products. Its parts are designed in-house and tested at its Carlsbad, California facility, and carry a 2-year warranty from the invoice date. In-stock orders placed before 3:00 PM Pacific ship the same business day. Returns need an RMA within 30 days of shipment and carry a 25 to 50 percent restocking charge, which is one more reason to confirm the checks above first. For a plug above 100A, a breaker-type plug, or a number you cannot find, call (855) 355-2724, Monday to Friday, 6AM to 5PM Pacific, with the nameplate details.

Safety when changing a bus plug

Plug-in busway stays energized along its length unless it is switched off upstream, and the switch on a plug only isolates the load side of that plug. De-energize the busway, apply lockout/tagout, and verify the absence of voltage before removing or installing a plug. Follow your site’s electrical safety program and the busway manufacturer’s instructions. This work is for qualified personnel only.

Square D bus plug cross reference FAQs

What replaces a Square D PQ3603 bus plug?

The catalogue lists BRAH part BPQ3603 as the substitute for Square D PQ3603, PQ3603R and PQ3603J: a 30A, 600V, 3-phase, 3-wire fusible plug without ground for I-Line I and II busway. If your plug has a ground, the number is PQ3603G and the BRAH part is BPQ3603G.

Can I replace a Square D bus plug with another brand?

Yes, if the replacement is made for the same busway family and matches the amperage, voltage, wire count and ground of the original. The BPQ parts above are listed as direct substitutes for the Square D PQ numbers shown against them. Similar looks are not evidence of fit; go by the catalog number and the busway nameplate.

Do the R and J suffix numbers need a different replacement?

Not in this catalogue. Each BRAH record lists the plain Square D number together with its R and J versions, and the BRAH part is listed as accepting Class H, R and J fuses. Order by amperage, voltage, wires and ground, then choose the fuses for your system.

What if my Square D plug is 200A or larger?

The table above covers 30A, 60A and 100A fusible plugs. The catalogue also lists a 200A ground kit (PQ200G) and a 200A neutral kit (PQ200N) for PQ plugs. For a plug at 200A or above, call (855) 355-2724 with the catalog number and we will check what is available.

How do I cross reference a plug with a missing label?

Work from the ratings instead. Read the busway nameplate for the series, take the amperage and system voltage from the panel schedule or drawings, and count the load-side conductors for wires and ground. With those facts you can pick the row in the table. Photos of the plug and the busway label help if you call for confirmation.

References

• UL 857, Busways: the UL standard covering busways and their plug-in devices.
• UL 248-1, Low-Voltage Fuses, General Requirements: the base standard of the series that defines low-voltage fuse classes.
• OSHA 29 CFR 1910.147: control of hazardous energy (lockout/tagout).
• NFPA 70E: standard for electrical safety in the workplace.