How to Identify the Correct Bus Stabs When Replacing Bus Plugs

Bus stabs are the copper contact fingers on the back of a bus plug that clamp onto the bus bars inside the busway and carry current into the plug. To pick the correct replacement, identify the busway manufacturer and the bus plug type, the plug amperage, and whether the stab sits on a phase (A, B or C) or on the neutral. BRAH Electric lists 10 stab parts for General Electric and Siemens / ITE bus plugs, shown in the table below.

BRAH replacement bus stabs by busway family

These are all of the parts in the bus plug stabs sub-category. Each one is listed for both fusible and breaker-type plugs of the family shown. The catalogue does not give an OEM part number for individual stabs, so match by the bus plug type printed on the plug (AC, SB, SL, FVK, UV or BOS) instead of a stab number.

The General Electric parts are also listed for BRAH’s own substitute plugs: BEC, BEB and BEL for the Armor Clad and Spectra families, and BEK for Type FVK. One part number is printed in the catalogue with asterisks, *FVKSTAB100A4*; it is the 100A neutral stab for FVK plugs.

What a bus stab does and how it wears

A plug-in busway has openings along its length where a bus plug can be attached. The stabs pass through the opening and grip each bus bar with spring pressure. All of the load current for that plug flows through those few contact surfaces, so the condition of the stabs decides how well the plug is connected.

Stabs that have lost tension, are pitted from arcing, or are discoloured from heat make a poor joint. A poor joint runs hot, and heat weakens the spring further. When the plug body, switch and fuse clips are still good, replacing the stabs and their insulators is a repair option for the families in the table.

How to identify the right stab

1. Busway manufacturer and plug type

Stab shape is specific to the busway design. A stab for a GE Spectra plug does not fit a GE Type FVK plug, even though both are General Electric. Read the type from the plug nameplate. The catalogue groups stabs into four families: GE Armor Clad / Spectra / Spectra Low-Amp (plug types AC, SB, SL), GE Type FVK from the Flex-A-Plug series, Siemens / ITE XL-U Series (type UV), and Siemens / ITE BD Series (type BOS). The Siemens parts are also listed for plugs badged Gould and Bulldog.

2. Plug amperage

Within a family, the stab changes with the amperage of the plug. For FVK plugs there is one stab for 30A to 100A and another for 200A. For UV and BOS plugs, kit 1 covers 30A to 100A and kit 2 covers 200A. For Armor Clad and Spectra plugs, ACSBSLN1 covers 30A to 200A and 400ASTAB covers 400A to 600A. Use the amperage on the plug nameplate, not the size of the fuses fitted.

3. Phase position: A, B, C or neutral

On Type FVK plugs the phase stab and the neutral stab are different parts. FVKSTAB100A and FVKSTAB200A are for the A, B and C phases. *FVKSTAB100A4* and FVKSTAB200A4 are for the neutral of a 4-wire plug only. On Armor Clad and Spectra plugs one stab serves any phase including the neutral. The Siemens kits contain three stabs and are listed for 3-wire or 4-wire applications.

4. Quantity

The GE stabs are single fingers, so count what the plug needs. ACSBSLN1 is rated 100A maximum per stab, and the catalogue states that 200A applications require two stabs per phase. A 4-wire FVK plug needs the phase stabs plus the separate neutral stab. The UVSTABKIT and BOSSTABKIT parts are complete sets of three stabs with their insulators.

5. Orientation

The stab records do not list a mounting orientation, so there is nothing to select for it when ordering a stab. Orientation does appear elsewhere in the catalogue: some neutral kits are made for vertical mounting plugs and others for horizontal. If you are replacing a neutral assembly together with a stab, check that kit’s description as well.

Stab insulators that go with the stabs

The insulator records state that the copper stabs are sold separately, so the single GE stab fingers and their insulators are two orders. If the plastic insulator is cracked, tracked or heat damaged, replace it at the same time. The catalogue lists seven stab insulators, each sold individually and without the copper stab.

At each amperage range the BOS insulator comes in two styles that differ in where the mounting hole sits, so compare with the old insulator before ordering. More on inspection is in the guide on when to replace bus plug insulators.

What to check before you order stabs

• Plug type: AC, SB, SL, FVK, UV or BOS, from the plug nameplate.
• Plug amperage: it decides which stab or kit in the family applies.
• Wires: 3-wire or 4-wire. A 4-wire FVK plug needs the separate neutral stab.
• Quantity: single fingers or a kit of three; two ACSBSLN1 per phase at 200A.
• Insulators: included in the UV and BOS kits, ordered separately for the GE fingers.

For Square D I-Line, Eaton / Cutler-Hammer or other plugs not in the table, see the Square D bus plug cross reference or the full bus plugs and parts range, or call (855) 355-2724, Monday to Friday, 6AM to 5PM Pacific. BRAH Electric is an aftermarket manufacturer, not an authorized distributor of GE or Siemens products. Parts carry a 2-year warranty from the invoice date, and in-stock orders placed before 3:00 PM Pacific ship the same business day.

Safety when working on bus stabs

Stabs connect directly to live bus bars. Remove the plug from the busway only with the busway de-energized, locked out and tagged out, and after a test for absence of voltage. Do not bend, file or modify a stab to make it fit a different busway. Stab replacement and plug installation are jobs for qualified electrical personnel working to the site safety program.

Bus stab FAQs

What are bus stabs on a bus plug?

They are the conductive fingers that connect the bus plug to the bus bars in the busway. Each phase has its own stab or pair of stabs, and a 4-wire plug has a neutral stab as well.

Can I modify a stab to fit a different busway?

No. Stabs are made for one busway design, and a reshaped stab will not hold the contact pressure it was built for. Use the stab listed for your plug type, or replace the plug with one made for that busway.

How many stabs does a 200A GE Spectra plug need?

The catalogue rates ACSBSLN1 at 100A maximum per stab and states that 200A applications require two stabs per phase. That is six stabs for the three phases of a 200A plug.

Do the Siemens stab kits include insulators?

Yes. UVSTABKIT1, UVSTABKIT2, BOSSTABKIT1 and BOSSTABKIT2 are each described as a complete set of three stabs with the associated stab insulators.

What if the plug nameplate is missing?

Read the busway nameplate for the manufacturer and series, and take clear photos of the plug, its stabs and the busway label. Send them to BRAH Electric or call with the details so the plug type can be confirmed before you order.

References

• UL 857, Busways: the UL standard for busways and associated fittings, including plug-in devices.
• OSHA 29 CFR 1910.147: the control of hazardous energy (lockout/tagout).
• OSHA 29 CFR 1910.333: selection and use of electrical work practices, including de-energizing and verification.
• NFPA 70E: standard for electrical safety in the workplace.