Grounding Monitor Interrupter (GMI)

Resources

• Campground and RV Park One-Pager
• Dealer One-Pager
• Board Sets Model Year 2028 Effective Date for GMI Enforcement

The Coming Impact of Grounding Monitor Interrupters (GMIs)

Background

The National Electrical Code (NEC) governs electrical installations in the United States and is updated and published by the National Fire Protection Association every three years. Article 551 of the NEC contains electrical safety requirements for RVs and RV parks and campgrounds.

Over the past six years, the NEC has received several public inputs to Article 551 addressing “hot skin” conditions. The 2023 edition of the National Electrical Code, updated language replacing “reverse polarity devices” to “loss-of-ground device.” However, because no loss-of-ground device was commercially available at that time, enforcement of this requirement was delayed.

Loss-of-ground devices were further defined as Grounding Monitor Interrupters, or GMI, per the 2026 edition of the National Electrical Code.

All RVs with 30-amp or 50-amp electrical services, beginning with model year 2028 will be required to install a GMI. Before electrical current can pass into the RV, the GMI checks the receptacle/electrical pedestal for a proper ground connection. A GMI also monitors the ground connection to the RV and, if that connection is lost, disconnects power to the RV. It is essential that manufacturers, dealers, and RV parks and campgrounds do their part to help provide for the safety of RVers and ensure that electrical service is available and uninterrupted – whether for testing, pre delivery inspections or for RV park and campground guests.

• What is a “Hot Skin” Condition?

  "Hot skin" is a term used to describe when an RV’s metal exterior, metal frame, or other metal items become electrified, which is a serious electrical safety hazard caused by improper grounding or electrical faults. The National Electrical Code and the RV industry continue to improve the electrical safety of RVs for consumers through new requirements like the GMI.

• What is a Grounding Monitor Interrupter?

  A GMI tests the receptacle it is plugged into to ensure it is wired correctly and has a proper ground connection. If incorrect wiring or a loss of ground connection is detected, the GMI will not allow electricity to pass through or will disconnect power if the loss of ground occurs during operation. 

• What Issues Will a GMI Address?

  For RVs, the GMI will address damage to a power cord, which the National Electrical Code refers to as a “feeder assembly.” Damage to a power cord and the use of dog-bone adapters (common terminology for a type of power cable cord adapter) causing a compromised electrical supply, were the most common reasons for including this update in the National Electrical Code.

  The GMI will also address a loss of ground at the RV pedestal/electrical receptacle or the presence of electrical current on the grounding conductor (wire). Under certain conditions, either of these two items can result in “hot skin.” 

• When Will this New Requirement Take Effect?

  The RV Industry Association adopted the 2026 Edition of the NEC, published in late September 2025, with an effective date for the GMI requirement of January 1, 2027, and mandatory enforcement at the start of each manufacturer’s respective model year 2028 production. At that point, all new RVs must have a grounding monitor interrupter installed. 

How Can Campgrounds and RV Parks Prepare for this New Requirement?

GMIs will be required on new 30-amp and 50-amp RV electrical systems under NEC Article 551, beginning with Model Year 2028 which will be available in mid-2027. GMIs will make reliable campground grounding more critical because they check the pedestal ground before allowing power to the RV and can interrupt power if the ground is compromised, high-resistance, or incorrectly wired.

As previously mentioned, this protects RV owners from “hot skin” conditions, where the RV frame or exterior becomes energized due to grounding or wiring faults. A pedestal that appears to work today may prevent a GMI-equipped RV from connecting tomorrow.

NEC Article 250, Grounding and Bonding, applies to campground grounding systems through NEC Article 551.76 and provides the safety rules needed to clear faults quickly instead of energizing metal equipment.

The first step you can take is to have a licensed electrician evaluate your entire electrical system, from the main service through the distribution equipment to every pedestal, rather than addressing sites one at a time. Grounding problems are usually systemic, and a property-wide evaluation tells you where you stand before GMI-equipped RVs begin arriving.

• Considerations and Actions for Campgrounds and RV Parks to Discuss with a Licensed Electrician

  Campground and RV Park owners and operators should ensure that each pedestal has a sound grounding path back to the main system, without opening the enclosure. This includes both the initial verification as well as ongoing maintenance. Campground and RV Park owners and operators should ensure that persons performing work on their systems (inspections, testing, troubleshooting, maintenance, and repairs) are properly trained, qualified, equipped, and otherwise in compliance with applicable laws, standards, and regulations such as state/local licensing requirements and OSHA electrical safety requirements.

  Depending on the qualifications of a campground’s or RV park’s maintenance staff, they may be able to routinely perform the following checks at each pedestal without opening the enclosure. Anything beyond these checks should be referred to a licensed electrician.

• Inspections and Tests to Consider

  Check Point	Tool Used	What You Are Checking For	What It Means
  Physical Check	Visual inspection	Inspect the receptacle for physical damage, overheating, corrosion, looseness, or any visible damage.	May indicate poor connections that can compromise the safety ground path.
  Ground Present	30-amp/50-amp Circuit Analyzer	Open Grounds; circuit analyzer will indicate ground presence at receptacle.	Safety risks of electrical shock, fire, and potential damage to electronics.
  Polarity Test	30-amp/50-amp Circuit Analyzer	Test receptacles for reverse polarity (Hot and Neutral wires swapped).	Provides expected flow of power into the RV, can create a severe hazard.
  Hot-to-Ground	Multimeter or plug-in tester	Voltage should read approximately 120V.	If it reads less than 114V, a wire may be broken or missing. Call a licensed electrician.

• Best Practices for Campground Owners

  Best practice is to have a licensed and insured electrician perform a complete inspection and routine maintenance on all pedestals at least annually to prevent "hot skin" hazards and costly system failures

  GMIs are complex and can search for and detect several different conditions beyond just testing for grounding. Although there are 30-amp and 50-amp circuit testers (also called “plug-in testers”) that you can use as referenced in the table above, they will not test for every potential condition that a GMI device will detect. Therefore, it is recommended that official UL-listed testing equipment specific to GMI devices be used once available. Remember, solely relying on a plug-in tester will only give you a partial answer as to the electrical system. A licensed electrician should be able to make reasonable assumptions about your susceptibility based on reviewing the entirety of the electrical system.

  All RV parks and campgrounds should take steps to address their electrical system, especially if it's been a while since the last full system evaluation, there have been unexplained outages or guest complaints, or the condition of the electrical system is unknown. If there is concern about the infrastructure, don't wait too long to get the system checked out. Rectifying issues could take months of planning; especially for a seasonal park, it could mean several unhappy RVers next summer before being able to address the issues in the off-season. It should be noted that the GMI device is simply raising the flag on issues that may have existed at the RV park for decades. This device isn't going to punish parks that don't have issues — it's just going to make the issues that do exist impossible to ignore. 

• Finding a Qualified Electrician

  Use a licensed and insured commercial electrical contractor with experience in campground or RV park electrical systems, not only residential service work. 

  Start by contacting your national or state campground association. These organizations may be able to recommend contractors with direct experience working on campground and RV park electrical systems.

  Consider using state license lookup tools and professional directories to confirm the contractor is properly licensed, insured, bonded, and familiar with current NEC requirements. 

  • Verify an active Master Electrician or Electrical Contractor license.
  • Consider reviewing professional association directories, such as NECA (National Electrical Contractors Association) or IEC (Independent Electrical Contractors), for commercial electrical contractors.

• Helpful Questions to Ask Before Securing Services

  Ask whether the contractor:

  • Is familiar with NEC Article 551 for RV parks and campgrounds and applicable OSHA electrical safety requirements, including Lockout/Tagout (LOTO) requirements.
  • Has experience working in Campgrounds and RV Parks and is familiar with their electrical systems.
  • Can evaluate pedestal grounding, neutral-to-ground isolation, wiring condition, lug torque, and generate a comprehensive inspection report.
  • Has test equipment needed to measure pedestal ground continuity and neutral loop resistance.

• Services to Consider Obtaining from a Qualified Electrician

  • Visual Inspection: Verify good inspection of the receptacle for physical damage, burns, overheating, tight connection points, and are free from any corrosion.
  • Pedestal ground continuity: Verify a low-impedance equipment grounding conductor path from each pedestal back to the source.
  • Neutral-to-ground isolation: Confirm neutral and safety ground are separated inside each pedestal and identify downstream bonding faults that may trip RV GMIs.
  • Neutral loop continuity: Measure the resistance of the grounding conductor path from each pedestal receptacle ground to neutral. Requires an earth ground tester or a GMI-specific tester available from GMI suppliers.
  • Mechanical lug re-torque: Inspect for wiring defects, heat stress, arcing, and tighten connections to manufacturer specifications.

Is Your Dealership Ready for GMI-Equipped RVs?

Starting with Model Year 2028 (available in 2027), new RVs will have Grounding Monitor Interrupters (GMIs). Regardless of where an RV is plugged in (dealership, campground, etc.), if the electrical power source has unaddressed grounding issues, a GMI-equipped RV will not accept power and everything in that RV that requires such power will either (1) not turn on if the electrical issue is detected prior to operation or (2) shut off if the electrical issue is detected while in operation. 

• What is a GMI & Why Does It Matter?

  • Safety Mandate: Required under the RV and RV Parks electrical standard, NEC Article 551, a GMI tests the electrical power source’s ground connection before allowing electricity to pass into the RV, continuously monitoring it during operation.
  • Prevents "Hot Skin": GMIs protect against severe electrical shock caused by improper grounding, damaged power cords, or incorrect wiring.
  • The Reality for Dealerships: GMIs do not cause electrical issues—they expose existing ones. An electrical power source that powers an RV today may leave a GMI-equipped RV in the dark tomorrow.

• In-House Staff Checkpoints Your Team May Be Able To Perform

  Routine non-invasive checks your maintenance team may be able to perform before calling a professional:

  Check Point	Tool Used	What You Are Looking For	Action Needed
  Physical Check	Visual Inspection	Damage; burning; corrosion; looseness	Call electrician if damaged
  Ground & Polarity	30A/50A Circuit Analyzer	Open grounds or swapped Hot/Neutral wires	Severe risk; call electrician
  Hot-to-Ground	Multimeter/Tester	Voltage should read ~120V	If <114, wire is broken/missing; call electrician

• Take Action: Partner with a Commercial Licensed and Insured Electrician

  Grounding issues are often systemic across a property. Rectifying infrastructure takes time—don't wait!

  1. Perform a Property-Wide Audit: Evaluate from the main service down to every electrical power source.
  2. Verify Grounding & Isolation: Test electrical power source ground continuity, neutral loop resistance, and neutral-to-ground isolation.
  3. Re-Torque Hardware: Check connections for heat stress, arcing, and proper specifications.

• Where will the GMI be located in the unit?

  Although different brands and floor plans may have the GMI in varying locations, there are certain parameters that all RVs must adhere to. Per the NEC Article 551, the GMI is to be permanently installed between the feeder assembly connection to the RV and before either the panelboard (if a transfer switch is not provided) or the transfer switch ahead of the panelboard. 

• What does my consumer need to know?

  Each dealer should communicate to their consumer that their Model Year 2028 unit is equipped with a GMI device. You will need to explain what it does, how it protects the consumer, and what to do if it turns the power off to the unit.