Updated on January 23, 2026
In the world of residential and commercial electricity, the Ground Fault Circuit Interrupter (GFCI) is the guardian angel of our electrical system. Unlike a standard circuit breaker, which protects your equipment from overloads and short circuits, the GFCI protects you—the human—from deadly electrical shock.
With the flood of technology in our homes in 2026—from induction cooktops and EV chargers to computers and appliances packed with advanced electronics—understanding the different RCD Types that power these GFCIs is more critical than ever. A Residual Current Device (RCD) is the core technology inside a GFCI that detects the fault. Choosing the wrong type won’t just cause annoying nuisance trips; it could fail to protect you when you need it most.
The international standard IEC 60755, which heavily influences the NEC (National Electrical Code), defines several classes of RCDs. Let’s break them down so you know exactly what your smart home needs.
A Complete Guide to GFCI & RCD Types in 2026
Each RCD type is engineered to detect different ground fault current waveforms. Modern electronics don’t leak current in a clean sine wave anymore, which means the classic GFCI you might have had for years could be obsolete for many of today’s circuits.
Type AC: The Legacy Standard
This is the most basic RCD type. It’s designed to detect purely sinusoidal AC ground faults, the kind you’d get from simple resistive loads like old-school incandescent bulbs or basic electric heaters. In my experience, for any modern installation in 2026, its use is almost entirely phased out.
- Protection: Detects standard alternating current (AC) sinusoidal faults (60 Hz).
- 2026 Use Case: Largely obsolete for new circuits. Only suitable for very specific, simple circuits with no electronics whatsoever.
- Symbol:
Type A: Today’s Minimum Standard
The Type A RCD is the logical successor to the Type AC. In addition to detecting standard AC faults, it can also detect pulsating DC ground faults. This type of leakage is common in most modern single-phase appliances with electronics: washing machines, dishwashers, microwaves, and power tools.
The 2026 National Electrical Code (NEC) effectively mandates Type A as the minimum standard for most circuits requiring GFCI protection in new homes.
- Protection: Covers everything Type AC does, plus pulsating DC faults.
- 2026 Use Case: The go-to standard for general-purpose outlets, lighting circuits, and most major appliances in a modern home.
- Symbol:
High-Immunity GFCIs: The End of Nuisance Tripping
Does your GFCI trip for no apparent reason, especially during a thunderstorm or when you power on multiple computers? You probably need a High-Immunity GFCI (sometimes marketed as “Super-Immunized” or SI). Technically, it isn’t a separate class but an enhancement built upon a Type A or Type F RCD.
These devices incorporate high-frequency filters, making them immune to ‘electrical noise’ and parasitic currents that aren’t a real safety threat but would cause a standard GFCI to trip. They are the definitive solution for circuits powering home offices, servers, or areas with a lot of cheap LED lighting.
- Protection: Typically based on Type A, adding immunity to nuisance trips from harmonics and high-frequency noise.
- 2026 Use Case: Ideal for home office circuits, home labs, and anywhere that uptime is critical.
- Symbol: Often uses the Type A symbol with additional markings like SI, Hpi, or K, depending on the manufacturer.
Type F: Protection for Modern Appliances
Type F is the next step up from a High-Immunity Type A. It’s specifically designed to protect circuits with single-phase variable frequency drives (VFDs), like those found in the latest inverter-driven HVAC systems, heat pumps, and high-efficiency washing machines.
It detects everything a Type A does but adds protection against high-frequency (up to 1 kHz) ground faults and can handle a smooth DC component of up to 10mA without being blinded.
- Protection: Covers all Type A faults, plus mixed-frequency faults common in inverter-driven motors.
- 2026 Use Case: Highly recommended for HVAC circuits (air conditioners, heat pumps) and high-end appliances with ‘inverter’ technology.
- Symbol:
Type B: The Ultimate Protection
The Type B RCD offers the most comprehensive protection, and it’s also the most expensive. It can detect all the previously mentioned fault types (AC, pulsating DC, mixed frequency) and adds the critical ability to detect **smooth DC ground faults**. This is the kind of fault that can be generated by EV chargers (EVSEs), three-phase Uninterruptible Power Supplies (UPS), and solar PV inverters.
Its use is mandated by the NEC for most EV charging locations if the charging station itself doesn’t include equivalent DC fault protection (often called RDC-DD or 6mA DC detection).
- Protection: The gold standard. Protects against AC, pulsating DC, high-frequency, and smooth DC faults.
- 2026 Use Case: Essential for EV chargers, solar inverter connections, and professional equipment with VFDs.
- Symbol:
RCD Types Comparison Chart (2026)
To help you decide which GFCI breaker to choose, I’ve put together this quick-reference table with all the key information.
| Type (Symbol) | Protection Level | Recommended Applications in 2026 | Estimated Price Range |
|---|---|---|---|
Type AC | Basic (Sinusoidal AC) | Obsolete for most uses. Only for legacy circuits with zero electronics. | $20 – $35 |
Type A | Standard (AC + Pulsating DC) | Outlets, lighting, cooktops, microwaves. The minimum required for homes. | $40 – $60 |
Type A-SI (High-Immunity) | Advanced (Type A + high-frequency filters) | Home office circuits (computers, routers, UPS), LED lighting. Prevents nuisance trips. | $60 – $100 |
Type F | High (Type A + high-frequency AC faults) | Inverter HVAC systems, heat pumps, high-efficiency washers and dryers. | $100 – $180 |
Type B | Total (Type F + smooth DC faults) | EV Chargers (EVSE), solar PV inverters, large UPS systems. | $250 – $500+ |
What GFCI Do I Need for My House in 2026? A Practical Guide
As an electrician, my advice is clear: segment your circuits and protect each one with the appropriate GFCI breaker. Installing a single GFCI for the whole house is bad practice that compromises both safety and reliability.
- General Lighting & Outlets: A Type A GFCI is the bare minimum. If you have a home office with computers, TVs, and game consoles on the circuit, I strongly recommend a Type A High-Immunity breaker to save yourself a lot of headaches.
- Kitchen (Cooktop, Oven) & Laundry: These circuits absolutely require a Type A GFCI. If you have high-end appliances with inverter motors (very common in 2026), a Type F would provide optimal protection.
- HVAC / Heat Pump: Nearly all modern units are inverter-driven. The correct choice here is a Type F GFCI breaker.
- Electric Vehicle (EV) Charging Station: The NEC is very strict here. You need a Type B GFCI breaker. The only exception is if your EV charger explicitly states it has an integrated RDC-DD that protects against DC faults greater than 6mA, in which case a Type A *might* be acceptable. When in doubt, I always install a Type B to ensure maximum safety.
Frequently Asked Questions (FAQ) about RCD Types & GFCIs
- What’s the difference between a GFCI and a standard circuit breaker?
- This is the most common question. A GFCI protects people from electric shock by detecting tiny ground faults (leaks of current). A standard circuit breaker protects the wiring and equipment from overloads (too much current) and short circuits. They serve different purposes and are both essential for a safe electrical system.
- Why does my GFCI keep tripping?
- It could be for several reasons: an appliance with a genuine ground fault, moisture in an outlet, or an incorrect GFCI type (e.g., a Type AC trying to handle an electronic device). If it trips for no obvious reason, a High-Immunity GFCI is often the fix. If the problem persists, call an electrician to perform an insulation resistance test on the circuit.
- GFCI Type A vs. AC, which is better for a house?
- Without a doubt, Type A. In 2026, a home is filled with electronics that generate non-sinusoidal fault currents. A Type AC GFCI might not detect these, creating a serious safety hazard. The small price difference is nothing compared to the massive increase in protection.
- What sensitivity should a GFCI have (5mA or 30mA)?
- This is a critical safety point. For personnel protection in US homes, a Class A GFCI is required by law. It is designed to trip when it detects a fault current between 4 and 6 milliamps (0.004A – 0.006A). Devices with a 30mA trip level are used for equipment protection (EGFPD), not for protecting people from shock in residential settings.
Conclusion: Don’t Skimp on Electrical Safety
Choosing the right GFCI has evolved from a simple code requirement to a crucial element for the safety and functionality of our 2026 smart homes. Investing in a higher-class RCD technology (Type A, F, or B) isn’t an expense—it’s an insurance policy for your family’s well-being.
While installing a Type B breaker on every circuit is costly overkill, protecting a modern laundry circuit with an old Type AC breaker is, frankly, negligent. The key, as always in this field, is to analyze what each circuit is powering and apply the correct technical solution. When in doubt, consulting with a licensed electrician isn’t just a recommendation; it’s essential.