Choosing the Best Replacement for Square D Bus Plugs Without OEM Delays

To replace a Square D fusible bus plug, match five things from the old plug and the busway: the I-Line busway series, the amperage, the voltage, the wire count and the ground. BRAH Electric lists 24 BPQ fusible plugs for I-Line I and I-Line II busway as fit-and-function substitutes for Square D PQ numbers, covering 30A, 60A and 100A in 240V and 600V versions. This guide covers what to match, the order of work for the swap, and the ground kits, neutral kits and small parts that go with these plugs.

What to match on a Square D I-Line bus plug

A replacement that differs from the original in any of these points is a different plug. Take the facts from the equipment itself where you can, because labels fade and plugs are changed in the field.

Two of these are easy to get wrong. The voltage on the plug is a maximum, so a 480V system takes the 600V part, and a 240V plug must not go on it. The wire count and ground are two separate things: a plug can be 3-wire with a ground, or 4-wire with no ground.

BRAH BPQ part numbers for Square D PQ plugs

The BPQ numbers are built the same way for all 24 parts. After BPQ3 comes 2 for 240V or 6 for 600V, then 03, 06 or 10 for 30A, 60A or 100A. Add G for a ground and N for the 4-wire version. The first column of part numbers links to the product page for the basic 3-wire plug.

The Square D numbers each part replaces, including the R and J suffix numbers, are in the Square D bus plug cross-reference table. Use that guide when you are starting from a number on a nameplate. You can also type the Square D number into site search or browse the fusible bus plugs listing.

How to replace a Square D bus plug: order of work

The steps below are the general sequence for changing a plug-in unit. They do not replace the busway manufacturer’s instructions or your site procedure, and the work is for qualified electricians.

1. Confirm the new plug before the shutdown. Compare its label with the old plug and the busway nameplate while the line is still running. Finding a mismatch during the outage costs far more time.
2. Plan the outage. Plug-in busway is live along its whole length, so the run has to be switched off upstream. Agree the window with production and identify every load fed from that run.
3. Isolate and prove dead. Open and lock the upstream device, apply tags, and test for voltage at the plug with a meter you have just checked on a known source.
4. Disconnect the load. Label the load conductors by phase, then free them and the conduit or cable fitting from the old plug.
5. Remove the old plug. Release it from the busway as the busway instructions describe and lower it clear. A bus plug can be heavy and awkward at height, so plan the lift.
6. Inspect the busway opening. Look at the bus bars and the plug-in opening for discoloration, pitting or damaged insulation. Report damage before fitting anything new.
7. Fit the new plug. Seat it with its switch in the off position, secure the mounting hardware, and check it sits square on the busway.
8. Reconnect and fuse. Land the conductors on the same phases, tighten terminals to the torque marked on the equipment, and fit fuses of the correct class and ampere rating.
9. Restore power. Close the door, remove locks and tags under your procedure, energize the run, then close the plug switch and check the load.

Ground and neutral kits for I-Line bus plugs

When the plug body and switch are sound, a kit can be the whole job. A ground kit adds a ground connection. A neutral kit converts a three-phase plug to 4-wire or replaces a damaged neutral. The 12 kits below are listed for I-Line I and II. For PQ fusible plugs the mounting style of the plug decides which neutral kit fits, so check whether yours is the newer vertical style or the older horizontal style.

Each kit is rated 600V maximum. The bus plug ground kits and bus plug neutral kits listings show them with photos, which helps when you are comparing a kit with the hardware in your plug.

Fuse clips and lugs to check while the plug is open

An outage is the time to look at the parts that carry current inside the old plug or the one next to it. Fuse clips that have lost tension or show heat marks, and lugs with damaged threads, are common reasons a plug runs hot. These universal parts are described as substitutes for a range of bus plugs and fusible switches, so compare the mounting and size with the part you are replacing.

See the full fuse clips and lug terminal kits listings for other sizes. The guide to choosing bus plug fuses covers fuse selection.

Before you order a Square D replacement

• Write down the full Square D catalog number, with every letter after the digits.
• Read the busway nameplate and confirm it says I-Line.
• Note the amperage and whether the plug is the 240V or 600V version.
• Open a de-energized plug and look for a neutral and a ground.
• If you need a PQ neutral kit, note whether the plug mounts in the vertical or horizontal style and the can size.
• Decide the fuse class and rating for the load. Fuses are a separate purchase.

In-stock orders placed before 3:00 PM Pacific ship the same business day, with shipping calculated at checkout. BRAH parts carry a 2-year warranty from the date of invoice. A return needs an RMA, must be made within 30 days of shipment, and is subject to a 25 to 50 percent restocking charge. BRAH Electric is an aftermarket manufacturer, designs and tests its parts in Carlsbad, California, and is not an authorized distributor of Square D or Schneider Electric. For anything not in the tables, call (855) 355-2724 with the part number, Monday to Friday, 6AM to 5PM Pacific.

Safety on I-Line plug-in busway

Treat every part of the busway and the line side of every plug as energized until it has been isolated upstream, locked out, tagged and tested. The handle on a bus plug disconnects the load only. Wear the protective equipment your site assessment calls for, and stop if the busway shows damage you did not expect.

Square D bus plug replacement FAQs

What is the BRAH replacement for a Square D PQ bus plug?

It is a BPQ fusible plug with the same amperage, voltage, wires and ground. For example BPQ3606 is the 60A, 600V, 3-wire part without ground and is listed as a direct substitute for Square D PQ3606. The cross-reference guide has every number.

Do I have to shut down the whole busway to change one plug?

Plan on it. The plug connects directly to bus bars that are live along the full run, and its own switch only opens the load side. Follow the busway manufacturer’s instructions and your site electrical safety program, which will normally require the run to be de-energized, locked out and tested.

Which neutral kit fits my Square D PQ plug?

It depends on the mounting style and size. PQ100N is listed for the newer vertical style in 30A, 60A and 100A cans. PQ60HN and PQ100HN are listed for the older horizontal style at 30A and 60A, and at 100A. If you cannot tell which style you have, send photos when you call.

Can I use a 600V bus plug on a 240V system?

The voltage rating is a maximum, so a 600V plug is not under-rated on a 240V system. The 240V and 600V versions are separate part numbers, though, and the fuses have to suit the plug and the circuit. The simpler rule is to replace like with like: order the version marked on the old plug unless an engineer has said otherwise.

What should I inspect when I pull the old plug?

Look at the stabs for pitting or heat discoloration, the fuse clips for tension and burn marks, the switch for smooth operation, the lugs for damaged threads, and the busway opening for marks on the bus bars. What you find tells you whether the fault was in the plug or is still in the busway.

References

• OSHA 29 CFR 1910.147: lockout/tagout requirements for servicing equipment.
• OSHA 29 CFR 1910.333: selection and use of electrical work practices, including de-energizing and verifying circuits.
• NFPA 70E: workplace electrical safety practices for qualified persons.
• UL 857, Busways: the UL standard covering busways and plug-in units.