Type B RCBO: The Essential Protection Solution for Safe EV Charger Installations

The Real-World Problem: “Why Does My EV Charger Keep Tripping?”

Scenario: Michael, a new Tesla owner, installed a 7kW home charging station last month. Initially, everything worked perfectly. However, after two weeks, his garage RCBO started tripping randomly during charging sessions—sometimes after 30 minutes, sometimes after 3 hours. His electrician replaced the RCBO twice, checked all connections, and confirmed the charger and vehicle were functioning normally. Yet the problem persisted.

The Diagnosis (by cnkuangya Senior Engineer Zhang Wei):
“This is one of the most common issues we see with modern EV installations. The problem isn’t faulty equipment—it’s incompatible protection technology. Standard Type A RCBOs cannot properly handle the DC residual currents generated by EV chargers. These DC components ‘blind’ the protection device, causing either nuisance tripping or, worse, failure to trip during actual faults.”

Part 1: Why EV Chargers Demand Special Protection

The Technical Challenge

EV chargers convert AC grid power to DC for battery charging. This conversion process inevitably creates:

• DC leakage currents from semiconductor switching
• High-frequency components from switching frequencies (typically 20-100kHz)
• Smooth DC faults that conventional RCDs cannot detect

The Safety Gap

Standard Type A RCBOs are designed to detect:

• AC sinusoidal residual currents ✓
• Pulsating DC currents (up to 6mA) ⚠️ Limited capability
• Smooth DC currents ✗ Cannot detect

Risk Scenario: A DC insulation fault develops in your charging cable. A Type A RCBO may fail to disconnect, allowing:

• Continued arcing and heat buildup
• Potential fire hazard
• Electric shock risk during maintenance

Regulatory Imperative

Latest standards mandate enhanced protection:

• IEC 62955: Requires DC 6mA detection for EV supply equipment
• IEC 60364-7-722: Specifies Type B RCD requirements for EV chargers
• National Electrical Code (NEC) Article 625: EV supply equipment protection requirements

Part 2: Type B RCBO Technology Deep Dive

How Type B RCBOs Work Differently

Type B RCBOs incorporate advanced sensing technology to detect:

1. AC Residual Currents (all frequencies up to 1kHz)
2. Pulsating DC Currents (full range, not limited to 6mA)
3. Smooth DC Fault Currents (from 0Hz upward)

cnkuangya Engineering Insight:
“Our Type B devices use a multi-frequency sensing core combined with digital signal processing. This allows us to distinguish between harmless charger operation currents and dangerous fault currents, dramatically reducing nuisance tripping.”

Key Performance Characteristics

Table 1: Protection Capability Comparison

Part 3: cnkuangya Engineer’s Installation Solution

Step-by-Step Selection Guide

Step 1: Determine Your Charger Requirements

Table 2: EV Charger Power vs. Protection Requirements

Step 2: Installation Best Practices

1. Location: Install within 3 meters of the EVSE (EV Supply Equipment)
2. Environment: IP65 rating for garage/exterior installations
3. Wiring:
   • Minimum 10mm² copper conductors for 32A circuits
   • Dedicated earth connection to charger
   • Surge protection upstream (for Type 2 installations)

Step 3: Commissioning Tests
Our engineers recommend:

• Test 1: RCBO test button verification (monthly)
• Test 2: Portable RCD tester with DC injection capability
• Test 3: Actual charging test with monitoring equipment

Part 4: cnkuangya Type B RCBO Product Range

Designed Specifically for EV Applications

Table 3: cnkuangya Type B RCBO Product Specifications

Engineering Advantage:
“Our devices incorporate adaptive threshold technology that learns normal charger operation patterns, further reducing false trips while maintaining protective sensitivity.”

Part 5: Troubleshooting Common Issues

Problem-Solution Pairs

Problem: RCBO trips immediately when charging starts
Solution: Check for incorrect wiring or equipment ground faults

Problem: Intermittent tripping after 30+ minutes
Solution: Likely thermal buildup; verify conductor sizing and connections

Problem: No trip during known fault condition
Solution: Test with Type B tester; replace if DC detection fails

Problem: Charger works but RCBO test button fails
Solution: Internal mechanism fault; replace unit immediately

FAQ Section

Q1: Can I use a regular RCBO for my EV charger if I add a DC-blocking device?

A: While DC-blocking filters can help, they’re not recognized as a complete solution by IEC 62955. Type B RCBOs remain the only fully compliant option for new installations after 2017. Retrofit installations may use Type A with filters, but this doesn’t provide equivalent protection.

Q2: How much more expensive is Type B protection?

A: Type B RCBOs typically cost 40-60% more than Type A equivalents. However, considering:

• Elimination of service calls for nuisance tripping ($150-300 per visit)
• Compliance with insurance requirements
• Future-proofing for next-generation chargers
  The additional investment is justified for any permanent installation.

Q3: My existing Type A RCBO hasn’t tripped in 2 years. Do I really need to upgrade?

A: Lack of tripping doesn’t indicate adequate protection. Type A devices may not detect developing DC faults until they become severe. We recommend testing with a Type B tester annually. Many electrical authorities now require Type B for all new EV charger installations.

Q4: Are there different sensitivity levels for Type B RCBOs?

A: Yes. While 30mA is standard for personal protection, some applications use:

• 100mA for equipment protection only
• 300mA for upstream protection
• 10mA for special applications (medical, etc.)

For EV chargers, 30mA Type B provides the optimal balance of personal protection and nuisance trip avoidance.

Q5: How do I test if my Type B RCBO is working correctly?

A: Three-level testing protocol:

1. Monthly: Press the test button on the device
2. Annually: Use a portable Type B RCD tester
3. Every 3 years: Comprehensive test by qualified electrician with:
   • AC test currents
   • DC test currents
   • Mixed frequency testing

Q6: Can Type B RCBOs be used for other applications?

A: Absolutely. Type B devices are also recommended for:

• Solar PV systems (inverters create similar DC currents)
• Variable speed drives
• Medical equipment
• Industrial rectifier circuits
• UPS and battery backup systems

Conclusion

From cnkuangya Senior Engineer Zhang Wei:
“The transition to Type B protection isn’t just about compliance—it’s about recognizing that EV charging technology has fundamentally changed electrical safety requirements. The DC components present in every charging cycle demand protection technology that can see the full spectrum of fault currents. Investing in proper Type B protection today prevents safety compromises tomorrow.”

Call to Action:
Contact cnkuangya’s technical team for a free EV charger protection assessment. Our engineers can:

1. Evaluate your existing installation
2. Recommend appropriate Type B solutions
3. Provide installation guidelines specific to your region
4. Offer bulk pricing for fleet operators

Resources:

• Download our “EV Charger Protection Checklist”
• Watch installation video tutorials
• Access IEC standard summaries
• Request on-site consultation (commercial clients)