Can Split Bolt Connectors Be Buried? | NEC Grounding & Splicing Guide

Can Split Bolt Connectors Be Buried Underground? NEC Code Explained

Split bolt connectors are one of the most widely used mechanical splicing devices in electrical distribution. Electricians use them every day to join copper and aluminum conductors, bond grounding electrodes, and splice feeders. But one of the most common questions we hear is: “Can split bolts be buried underground?”

The short answer is: Yes — but only when properly insulated and installed according to NEC 110.14(B). In this article, Conversions Tech explains what the National Electrical Code (NEC) requires, how to insulate buried split bolt splices, and when to consider alternative connectors.

NEC Requirements for Underground Splices

The National Electrical Code (NEC) governs how splices must be made in underground installations. Section 110.14(B) states that “Conductors shall be spliced or joined with devices identified for the use or by brazing, welding, or soldering with a fusible metal.” For split bolts, this means:

• The split bolt must be UL-listed for the conductor type (copper only, or copper/aluminum).
• The connection must be insulated to provide equivalent dielectric strength and protection as the conductor insulation.
• The splice must be accessible unless otherwise permitted by code.

In other words, a raw metal split bolt cannot simply be buried in soil — it must be properly insulated to pass inspection and to prevent corrosion or failure.

Why Split Bolts Require Insulation Underground

Unlike insulated mechanical lugs, split bolts are bare metal connectors. When placed underground, bare copper or bronze is exposed to moisture, soil minerals, and corrosive conditions. Without protection, this can lead to:

• Galvanic corrosion between dissimilar metals (copper/aluminum splices).
• Accelerated oxidation reducing conductivity.
• Insulation failure due to no dielectric covering.
• Inspection violations for non-code-compliant burial.

The solution is simple: wrap the splice with a combination of rubber insulating tape and vinyl electrical tape. This restores dielectric strength, seals out moisture, and meets NEC guidelines.

How to Properly Insulate Split Bolts for Direct Burial

1. Install the split bolt correctly: Strip conductors cleanly, insert fully, and tighten to the manufacturer’s torque spec.
2. Apply rubber tape: Wrap the connector fully with self-fusing rubber tape, overlapping by 50%. This builds insulation thickness equivalent to the conductor jacket.
3. Add vinyl tape: Overwrap the rubber with PVC vinyl tape to provide abrasion resistance and a smooth finish.
4. Check coverage: Ensure no part of the split bolt is exposed before burial.

👉 For copper/aluminum splices, always use a tin-plated split bolt connector to avoid galvanic corrosion.

Alternatives to Split Bolts in Underground Applications

Although split bolts are acceptable when taped, many contractors prefer connectors specifically designed for underground or direct burial. Alternatives include:

• Compression connectors with heat shrink — crimped lugs or splices with adhesive-lined shrink tubing.
• Insulated multi-tap connectors (e.g., Polaris lugs) — factory-insulated blocks rated for direct burial.
• Underground splice kits — gel-filled or resin kits that encapsulate the connection completely.

However, split bolts remain popular because of their availability, low cost, and ability to handle a wide conductor range.

When Split Bolts Are Acceptable Underground

Split bolts can be buried underground in the following conditions:

• They are UL/CSA listed for the conductor material being spliced.
• The splice is properly insulated with rubber and vinyl tape.
• Approved by the AHJ (Authority Having Jurisdiction) in your area.
• The installation meets all applicable NEC requirements.

In practice, many inspectors allow taped split bolts for grounding and feeder splices, provided the insulation is properly applied and the connector is listed.

Best Practices for Underground Split Bolt Splices

• Use tin-plated split bolts for copper-to-aluminum connections.
• Always torque to manufacturer specifications.
• Wrap generously with insulating tape — two layers minimum.
• Keep records of conductor size and connector size used for inspection.

FAQs: Split Bolts and Underground Use

Are split bolts UL-listed for direct burial? Most split bolts are listed for splicing and grounding but require additional insulation to be suitable for burial. Always check the product listing. Can you bury a copper split bolt directly? No. Bare copper or bronze connectors must be insulated before burial to prevent corrosion and meet NEC requirements. What tape should I use? Start with self-fusing rubber tape for dielectric strength, then add vinyl tape for abrasion resistance. Are there better alternatives underground? Yes — insulated multi-tap connectors and compression splices with heat shrink are often used. But properly taped split bolts remain code-compliant and cost-effective.

Conversions Tech Split Bolt Connectors

At Conversions Tech, our split bolt connectors are manufactured from high-conductivity copper alloys, available in bare or tin-plated finishes, and cover conductor sizes from 6 AWG to 600 MCM. All are UL/CSA listed and designed for safe, code-compliant splicing in both above-ground and underground applications (when properly insulated).

Need underground splicing solutions?
Browse our full split bolt connector catalog and choose copper or tin-plated versions for your job. Fast shipping and competitive pricing from Conversions Tech.