EVSE ground fault protection is built into the equipment as a required safety function, not added as a convenience. The unit monitors for current leaking out of the intended circuit and for the integrity of the protective earth connection, and it opens its contactor when either is wrong. A charger that refuses to start, or stops partway through, is often doing precisely what it was designed to do.
What the equipment is actually watching
Leakage detection compares the current flowing out against the current returning. In a healthy circuit they match. If some current is finding another path, to earth or through a person, the difference appears and the device disconnects. Separately, the equipment verifies that a protective earth connection exists and has acceptable continuity, because the vehicle’s body and the charging connector depend on that path during a fault. Both functions run continuously throughout a session, not just at the start. Thresholds are set low enough to act before a shock becomes dangerous, which is why small leakage currents matter here. Detection is deliberately fast, because the whole point is to interrupt the circuit before a person in contact with the vehicle is harmed by it.
Why this matters more than for ordinary appliances
Charging involves a large current, a connector handled by people, cables that lie on wet ground, and a vehicle that is a large conductive object someone may be touching. The consequences of an undetected fault are therefore more serious than for a lamp. The protection thresholds and response behavior for this equipment are defined in the standards it is listed to, which is another reason to buy equipment carrying a recognized testing laboratory mark rather than a generic import. Connector contacts are also exposed during insertion, which is another reason the equipment verifies conditions before energizing anything. A missing earth also means the vehicle body may not be held at a safe potential, which is precisely the condition the monitoring exists to catch.
Interaction with upstream protection
Where a receptacle outlet requires ground fault circuit interrupter protection under the applicable code, the result is protection both upstream and inside the equipment. Those two devices can interact, and nuisance tripping of the upstream device is a well-known complaint. It is not always a fault: some equipment produces small leakage currents during normal operation that an upstream device interprets as a problem. This is one of several reasons hardwired installations are often preferred, and it is a question to raise with your installer rather than to solve by removing protection. Discussing the configuration with your installer before purchase avoids discovering the conflict after the wall is closed up. Nuisance tripping that begins suddenly on an installation that worked for years usually indicates something has changed, such as water ingress or a degraded termination.
Diagnosing a unit that keeps stopping
Work outward from the most likely causes. Water in the vehicle inlet or in the connector is extremely common, particularly after rain or a car wash, and drying it often resolves the problem entirely. Damaged cables, a cracked connector body, a corroded receptacle or a poor earth connection at the panel are next. A vehicle fault can also cause it, so trying a different station tells you a lot. What never helps is bypassing protection, and any device sold to defeat a ground fault trip should be treated as dangerous. Trying the same vehicle on a different station, and a different vehicle on your station, isolates the fault quickly.
Installation details that prevent trouble
Make sure the equipment grounding conductor is properly sized, terminated and continuous, since a marginal earth path is a frequent cause of intermittent refusals. Avoid adapters and extension cords, which add interfaces where moisture collects. Mount the unit so the cable is not dragged through puddles and so the connector can be stowed off the ground. Where outdoor installation is involved, use equipment listed for wet locations and enclosures rated for the exposure, and follow the manufacturer’s mounting instructions on orientation and height. Conduit that drains water into the enclosure is another frequent cause, and it is easy to overlook because it only appears after rain.
What to check before you act
- Check the vehicle inlet and connector for water or debris first.
- Inspect the cable and connector body for cracks or damage.
- Verify the equipment grounding conductor is continuous and properly terminated.
- Never install any device intended to defeat ground fault protection.
Common questions
Why does my charger stop after it rains?
Water in the vehicle inlet or connector is the usual reason. The leakage detection is working correctly; dry the inlet and connector thoroughly and try again.
Can I remove the upstream GFCI breaker to stop nuisance trips?
No. Where the code requires that protection it must remain. Discuss the interaction with your installer, since a hardwired installation may avoid the conflict entirely.
The practical takeaway
Read a refusal to charge as a report rather than a malfunction. Check for water first, then the cable, connector and earth path, and resolve upstream protection conflicts with your installer. Never fit anything designed to defeat the protection.
References and further reading
- CDC and NIOSH: shock hazards and the role of ground fault protection
- NFPA: code requirements for ground fault protection and equipment grounding
- OSHA: grounding and ground fault protection requirements
Numerical scenarios are illustrative unless identified otherwise. Follow the exact product instructions; component ratings and local installation requirements can differ.
