Grounding and Bonding Requirements for EV Chargers in Michigan

Grounding and bonding are foundational electrical safety requirements that govern every EV charger installation in Michigan, from residential Level 1 outlets to commercial DC fast charging stations. These requirements are established under the National Electrical Code (NEC) and enforced through Michigan's Electrical Administrative Act, with specific provisions for electric vehicle supply equipment (EVSE) found in NEC Article 625. Understanding how grounding and bonding interact — and where the two functions differ — is essential for any installation that must pass Michigan Bureau of Construction Codes inspection.

Definition and scope

Grounding refers to the intentional connection of electrical equipment and conductors to the earth, establishing a reference voltage and providing a low-impedance fault current path. Bonding refers to the permanent joining of metallic parts — conduit, enclosures, equipment frames — to ensure electrical continuity and the ability to safely conduct fault current. Although the two concepts are closely related, NEC Article 100 defines them separately, and the failure to distinguish them is one of the most common inspection deficiencies in EVSE installations.

For EV chargers installed in Michigan, grounding and bonding requirements draw from:

The scope of these requirements covers every conductively connected element of an EVSE installation: the service entrance, panel, branch circuit, conduit system, charger enclosure, and — where applicable — the vehicle connector hardware itself. For a broader look at how Michigan's electrical regulatory framework is structured, the regulatory context for Michigan electrical systems provides foundational orientation.

Scope boundary: This page applies to EV charger installations within Michigan's jurisdiction under state-adopted electrical codes administered by LARA and enforced by licensed electrical inspectors. It does not address federal installation standards for EVSE manufacturers (which fall under UL 2594 and UL 2202 product listings), federally funded charging corridor projects governed by FHWA rules, or installations in adjacent states. Installations on tribal lands within Michigan may follow separate jurisdictional frameworks not covered here.

How it works

The grounding system for an EV charger operates in two coordinated layers.

Layer 1 — Equipment Grounding Conductor (EGC): NEC 250.118 specifies acceptable types of EGCs, including copper conductors, rigid metal conduit (RMC), intermediate metal conduit (IMC), and electrical metallic tubing (EMT) when used as a wiring method. For a 40-ampere EVSE circuit — the most common Level 2 configuration — NEC Table 250.122 requires a minimum 10 AWG copper EGC. For a 60-ampere circuit, the minimum rises to 10 AWG; for a 100-ampere circuit, the minimum is 8 AWG copper. These minimums can increase if the overcurrent device is upsized or if voltage drop calculations require larger conductors.

Layer 2 — Grounding Electrode System: NEC 250.50 requires that all grounding electrodes present at a structure be bonded together into a single system. Where a sub-panel or garage panel is installed to serve an EV charger — a common configuration described in detail at garage subpanel for EV charging in Michigan — the grounding electrode conductor must connect that panel to the grounding electrode system at the service.

Bonding of metallic enclosures, conduit fittings, and junction boxes follows NEC 250.8 (connection methods) and 250.96 (bonding of enclosures). Locknuts alone are not considered a bonding method in most inspectors' interpretations; listed bonding bushings or bonding locknuts are required at service equipment and where conduit enters enclosures.

Common scenarios

Scenario 1 — Residential garage, Level 2, 240 V / 40 A circuit:
The most prevalent Michigan installation involves a 40-ampere breaker feeding a Level 2 EVSE in an attached or detached garage. NEC 625.54 requires GFCI protection for all 120-volt and 240-volt receptacles used for EV charging — a protection type also addressed at EV charger GFCI protection in Michigan. The EGC must be continuous from the panel to the EVSE enclosure, and any metallic conduit must be bonded at both ends with listed fittings.

Scenario 2 — Outdoor pedestal charger, commercial property:
Outdoor installations require weatherproof enclosures rated NEMA 3R minimum, and the grounding system must account for a grounding electrode at the pedestal location if the feed exceeds 100 feet from the service — a threshold that triggers NEC 250.32 considerations for separate structures. The conduit system running underground is typically PVC Schedule 40 or 80, which provides no grounding path, making a dedicated EGC inside the conduit mandatory. See outdoor EV charger wiring and weatherproofing in Michigan for related weatherproofing requirements.

Scenario 3 — DC fast charger, 480 V three-phase:
High-power DCFC installations operate at 480 V three-phase and draw 100 to 350 amperes or more. At these levels, the EGC sizing under NEC Table 250.122 is substantially larger, and the bonding of the transformer secondary — if a step-down transformer is used — must comply with NEC 250.30. These installations require plan review and inspection by Michigan-licensed electrical inspectors, a process detailed at EV charger electrical inspection in Michigan.

Decision boundaries

The following structured breakdown identifies the code-driven decision points that determine grounding and bonding method selection:

  1. Wiring method selection: Metal conduit systems (RMC, IMC, EMT) can serve as the EGC if installed with listed fittings per NEC 250.118. PVC conduit, flexible conduit, and liquidtight flexible conduit require a separate copper EGC inside the raceway.

  2. Detached structure rule: NEC 250.32 applies when the EVSE is in a structure separate from the main building (e.g., a detached garage or carport). A grounding electrode system must be established at the separate structure, and the neutral and ground must remain separate at the sub-panel — they must not be bonded together as they are at the service entrance.

  3. EVSE with integrated GFCI vs. branch circuit GFCI: Some listed EVSE units include internal GFCI protection satisfying NEC 625.54. When the unit provides GFCI, a GFCI breaker at the panel is not required but may still be installed. The EGC requirement is unchanged regardless of GFCI source.

  4. Sizing EGC for upsized overcurrent protection: If the installer upsizes the circuit breaker beyond the minimum required for the EVSE load — a common practice when future-proofing for higher-output chargers — the EGC must be sized to the larger breaker rating per NEC Table 250.122, not the actual EVSE nameplate amperage.

  5. Listed connectors and terminations: NEC 250.8 prohibits the use of sheet-metal screws for bonding connections. All EGC terminations at enclosures must use listed lugs, bonding bushings, or other listed bonding devices. This point is a recurring source of failed inspections in Michigan.

The how Michigan electrical systems work conceptual overview provides context for understanding how grounding and bonding fit within the broader architecture of residential and commercial electrical systems. For installations requiring a permit — which includes virtually all EVSE work in Michigan — the EV charger permit requirements by county in Michigan outlines the jurisdiction-specific filing procedures that accompany grounding and bonding plan submissions.

For a complete overview of EVSE electrical installation standards across Michigan, the Michigan electrical code EV charger Article 625 page covers the full scope of Article 625 provisions. The EV charger NEC code compliance in Michigan page addresses how inspectors apply NEC requirements statewide.

Homeowners and facility managers researching grounding and bonding in the context of a full installation project will find the Michigan EV charger authority home a useful starting point for navigating all related technical topics.

References

📜 12 regulatory citations referenced  ·  ✅ Citations verified Feb 25, 2026  ·  View update log

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