Grounding Accessories and the NEC: Bushings, Pigtails, Bonding Jumpers, and Rebar Clamps

Most grounding failures on inspection are not the electrode — they are the small hardware between the electrode and the equipment: the bushing that should have been a grounding bushing, the device that was never pigtailed, the screw that only caught one thread. This guide walks through the accessories in our Grounding Accessories collection and the NEC article that governs each one.

Insulated grounding bushings — NEC 250.97 and 250.92

A grounding bushing threads onto a conduit end inside an enclosure and gives you a lay-in lug to land a bonding jumper. The NEC requires that bonding path in two places:

• 250.97 — circuits over 250 volts to ground. Where a raceway lands in a concentric or eccentric knockout (the punched rings in a panel or box), a locknut alone is not accepted as the bonding means; a bonding jumper to a grounding bushing (or a bonding locknut/wedge) is required. The exception permits omitting it only where the knockouts are tested for bonding or where the enclosure has no rings.
• 250.92(B) — service equipment. On the line side of the service disconnect, standard locknuts are never enough. Grounding bushings with bonding jumpers, bonding locknuts, or bonding wedges are required at every metal raceway termination.

The insulated part — a 150°C thermoplastic throat — satisfies NEC 300.4(G): conductors 4 AWG and larger entering an enclosure must be protected by an insulating bushing or fitting. One part does both jobs. Size the bonding jumper from Table 250.102(C)(1) (service) or Table 250.122 (feeders and branch circuits), and use a lug rated for the conductor material — dual-rated Cu/Al lugs are standard on this class.

Grounding pigtails and grounding screws — NEC 250.146 and 250.148

250.148: where an equipment grounding conductor enters a box, it must be connected to the box (metal boxes) and spliced so that removing a device — a receptacle, switch, or fixture — does not interrupt the ground to anything downstream. That is the reason for the pigtail: the EGCs are joined together with a short tail that lands on the device, so the device is never in series with the grounding path.

250.146 covers bonding the receptacle's grounding terminal to the metal box. A pigtail and a listed grounding screw in the box's tapped 10-32 hole is the default method. The screw itself is governed by 250.8(A): connections must be made with listed pressure connectors, listed clamps, exothermic weld, machine-screw fasteners engaging not less than two threads or secured with a nut, or thread-forming machine screws engaging not less than two threads. Drywall screws and sheet-metal screws are explicitly excluded (250.8(B)). A green combination-head 10-32 x 3/8 grounding screw in a factory-tapped box hole meets the rule; a self-tapper through a knockout does not.

Our 12 AWG solid pigtails ship with the thread-forming green screw attached; the 100-count 10-32 screws cover boxes that arrive tapped but bare.

Water heater bonding kit — NEC 250.104(A) and 250.68(B)

Metal water piping must be bonded to the service grounding electrode system (250.104(A)), and where a section of pipe is likely to be removed — a water heater, a meter, a filter housing — 250.68(B) requires that the bonding path remain continuous with a jumper around the removable section. A water heater bonding kit is that jumper: two listed pipe clamps and a length of copper conductor sized per 250.104(A) (Table 250.102(C)(1), commonly 6 or 4 AWG on residential services), spanning hot to cold so the piping stays bonded when the heater comes out. Many jurisdictions also cite it for 250.104(B) bonding of the gas piping via the appliance. Install the clamps on clean pipe, not on fittings, and where they will stay accessible.

Braided bonding jumpers — NEC 250.98 and vibration

Flat tinned-copper braid with lugs at each end is the right jumper wherever the bonded parts move relative to each other: across raceway expansion fittings (250.98 requires them to be bonded), across vibration-isolated equipment mounts, between a swing door and a metal enclosure body, and on telecom racks and cabinets. Size the braid for the equipment grounding conductor required by 250.122 for the largest circuit involved; the braid's cross-section is marked in AWG equivalent. Lug holes are typically 1/4" or 3/8"; match them to the bonding lug or stud, and torque per the lug.

Rebar lay-in ground clamps — NEC 250.52(A)(3) and 250.68(C)(3)

The concrete-encased electrode ("Ufer ground") is 20 feet of 1/2" or larger rebar in a footing, and it is required to be used where present (250.50). The GEC connects to it either inside the concrete — which calls for a connector listed for concrete encasement, such as an irreversible compression figure-6 or a listed rebar clamp — or at a rebar stub extended out of the footing per 250.68(C)(3), where a lay-in bronze rebar clamp is the standard termination. The clamp must be listed for direct burial/concrete if it will be encased or buried, sized for the rebar diameter (typically #3–#8) and the conductor range (10 AWG through 2 AWG covers residential and light-commercial GECs). The connection at a stub must remain accessible unless it is a listed compression or exothermic connection.

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Related: Irreversible Compression Grounding — Where, How, and Why · Split Bolt Connectors and the NEC. Products: Grounding Accessories.