Introduction: why the issue of RCDs in the garage is controversial

For most car owners, a garage is not just a place to park, but a full-fledged workshop with power tools, a welding machine, chargers and even a mini-boiler room. And if everything is more or less clear with sockets in the apartment, then Do you need an RCD in the garage? - a question that will divide electricians into two camps. Some argue that you can’t do without it because of the increased danger of electric shock, others call it “a waste of money” for a room where no one lives permanently.

The legislative framework also adds to the confusion: PUE (Electrical Installation Rules) are revised every few years, and local energy inspectors interpret the standards differently. For example, in 2026, the requirements for garage cooperatives became more stringent, but “gray areas” remained for individual buildings. We analyzed current regulations, interviewed practicing electricians and compiled a checklist that will help you make an informed decision - taking into account garage type (metal, brick, with basement), loads (3 kW or 15 kW) and even climatic conditions (humidity, risk of flooding).

PUE 2026: what the law says about RCDs in the garage

The main document regulating the requirements for electrical installations is PUE 7th edition (as amended 2026). In it, garages are classified as "premises with increased danger" (clause 1.1.13) due to a combination of three factors:

  • 🔌 Availability of metal structures (car body, workbenches, shelves), which can become current conductors.
  • 💦 High humidity — even in a dry garage, condensation on the walls in winter or puddles after washing the car create a risk of leakage.
  • ⚡ Using powerful equipment (welders, compressors, heaters), which is often connected via extension cords.

According to PUE 7.1.71, RCD is required in the following cases:

⚠️ Attention: If the garage is connected to the network via air line (and not an underground cable), then the RCD with leakage current no more than 30 mA required even for single-phase 220V network - this is a new tightening in 2026, associated with an increase in the number of fires due to old power lines.
Garage type Requirement PUE 2026 Recommended RCD leakage current
Individual (brick, blocks) Recommended but not required* 30 mA (for sockets), 100 mA (for lighting)
Metal (container, box) Required 10–30 mA (due to risk of touching the housing)
With basement/cellar Required (wet zone) 10 mA (basement), 30 mA (main room)
Garage cooperative (shared network) Required at the request of energy supervision 30 mA (input) + 100 mA (per groups)

* Exception: If the garage is used only for vehicle storage (no power tools or outlets), an RCD is not required. But in practice, such cases are rare - even to recharge the battery you need an outlet.

📊 What type of garage do you have?
Brick/block
Metal (container)
With basement/cellar
Wooden
Other

When an RCD in a garage is useless (or even dangerous)

Yes, there are situations when installing an RCD not only will not help, but will also create additional risks. Here 3 caseswhen it is better to abandon it or use alternatives:

  1. Old wiring with frequent leaks. If the garage has aluminum wiring from the 1980s, the RCD will false alarm every 10 minutes. In this case, you must first replace the cable with VVGng-LS 3×2.5 (for sockets) or VVGng-LS 3×1.5 (for lighting).
  2. Connection via generator. Many RCDs do not work with autonomous power supplies (gasoline generators, inverters). Here we need special models with markings "G" (for example, ABB F204 G).
  3. High starting current welding machine. Cheap RCDs (electromechanical) can burn out when connected to a transformer welder. Solution - selective RCD (with delay) or differential machine.
💡

If the lights in your garage are often turned off, install voltage control relay (for example, Bison RKN-1-16-01) - it will protect equipment from surges better than an RCD.

One more nuance: in garages with three-phase network 380V (for example, for machine tools) RCD necessarily, but it needs to be connected for each phase separately or use a four-pole device (for example, IEK VD1-63 4P 30mA). At the same time for three-phase motors (compressors, lathes) the leakage current must be at least 100 mA - otherwise they will turn off at startup.

How to choose an RCD for a garage: 5 criteria

If you decide to install an RCD, here step-by-step algorithm selection taking into account the specifics of the garage:

Determine the type of network (220V or 380V)|

Calculate total load (kW)|

Select leakage current (10, 30 or 100 mA)|

Check compatibility with the machine (rated value of the RCD ≥ rating of the machine)|

Consider climatic conditions (for wet garages - IP44 and above)

-->

1. Type of RCD: electromechanical or electronic?

  • ⚡ Electromechanical (for example, Legrand DX³ 40A 30mA) - more reliable, as it works without power. Suitable for garages with unstable voltage.
  • 🔋 Electronic (for example, IEK VD1-63) - cheaper, but requires power to work. It is dangerous if there are frequent power outages in the garage.

2. Leakage current:

  • 🔌 10 mA - for wet areas (basement, sink), but may cause false alarms.
  • 🔌 30 mA - the best option for socket groups.
  • 🔌 100–300 mA - for introductory RCD (protects against fire, but not against electric shock!).

3. Rated current: must be one step higherthan that of an automatic machine. For example, if the machine is on 25A, take the RCD to 40A.

4. Number of poles:

  • 🔌 Bipolar - for single-phase 220V network.
  • 🔌 Four-pole — for a three-phase network 380V.

5. Additional options:

  • 🛡️ Surge protection (labeling "S") - relevant for garage cooperatives with poor networks.
  • ❄️ Frost resistance (up to -25°C) - if the garage is not heated.
What happens if you install an RCD with a leakage current of 100 mA instead of 30 mA?

A 100 mA RCD will not protect a person from electric shock (the threshold for noticeable current is 5–10 mA, lethal current is 50–100 mA). His task is prevent fire in case of leakage to the housing or short circuit. For the safety of people in the garage necessarily you need to install an additional 30 mA RCD on the socket groups.

RCD connection diagrams in the garage: 3 options

The choice of scheme depends on network type (220V or 380V), number of consumers and budget. Let's look at the three most common options with their pros and cons.

Scheme 1: One RCD at the input (budget option)

Suitable for small garages with loads up to 5 kW and 1–2 sockets.



[Input circuit breaker] → [RCD 40A 30mA] → [Group circuit breakers]

Pros: cheap, easy to install.
Cons: When there is a leak, the entire garage shuts down, making it difficult to find the problem area.

Scheme 2: RCD + differential circuit breakers (optimal)

Ideal for garages with division into zones (lighting, sockets, basement).



[Input circuit breaker] → [RCD 63A 100mA (fire)]


→ [Automatic 16A] → [RCD 25A 30mA] → Sockets


→ [Automatic 10A] → Lighting (without RCD)

Pros: selectivity (only the problematic line is switched off), high security.
Cons: more expensive, requires more space in the panel.

Scheme 3: RCD for three-phase 380V network

Relevant for garages with machines, compressors, welders.



[Input circuit breaker 3P] → [RCD 4P 100mA] → [Phase circuit breakers]


→ [30mA RCD for 220V sockets]

Important: for three-phase motors you need to use selective RCD (with delay 100–300 ms), otherwise they will turn off at startup.

💡

If there is one in the garage welding machine, connect it via separate line with differential machine (for example, ABB DS201 C16 30mA) - this will prevent false positives.

Typical mistakes when installing an RCD in a garage

Even experienced electricians sometimes make mistakes that nullify all protection. Here TOP-5 misses and how to avoid them:

  1. RCD without grounding. The RCD works without grounding, but does not provide complete protection. Paired with him necessarily you need to install a circuit breaker. For example, if a phase breaks through to the machine body, the RCD will turn off the power, but without grounding, the body will remain energized until it trips.
  2. Zero and phase are mixed up. If you connect the zero at the top and the phase at the bottom, the RCD won't work. Correct connection: phase and neutral must go from above, load - from below.
  3. Test button missing. Every month you need to check the RCD by pressing a button "T". If it does not work, the device is faulty.
  4. RCD for lighting with DRL lamps. Gas-discharge lamps (DRL, DNAT) leak current during startup. Use for them separate line without RCD or switch to LEDs.
  5. Ignoring temperature conditions. In an unheated garage in winter, an RCD may freeze and stop working. The solution is an insulated shield or models with an extended temperature range (for example, Schneider Electric Acti9 iID).
⚠️ Attention: If it is in the garage voltage stabilizer, RCD needs to be installed after him, not before. Otherwise, it will respond to interference created by the stabilizer.

RCD alternatives: when are they more profitable?

RCD is not the only method of protection. In some cases differential automata or insulation monitoring relay turn out to be more effective. Let's compare:

Device Pros Cons When to use
RCD Cheaper than a difavtomat, you can connect several lines Occupies 2 modules, requires a pair connection with the machine For garages with a simple layout (1–2 groups)
Differential automatic Compact (1 module), protects against short circuits and leaks More expensive, more difficult to replace if broken For garages with limited space in the panel
Insulation monitoring relay (for example, RKI-1M) Monitors insulation resistance in real time Does not turn off the power, only signals For industrial garages with constant monitoring
Grounding + circuit breakers Reliable if the grounding is good Does not protect against direct contact For metal garages with a ground loop

For example, if in the garage only lighting and one socket, enough differential circuit breaker ABB DS201 C16 30mA. And for the workshop with welder, compressor and heater better combination: input RCD 100mA + group RCD 30mA.

FAQ: Frequently asked questions about RCDs in the garage

❓ Is an RCD necessary if there are only light bulbs and no sockets in the garage?

If the wiring is new and there is no risk of flooding, you can do without an RCD. But if the lamps gas-discharge (DRL, DNAT) or the wiring is old, it’s better to install fire protection RCD 100 mA.

❓ Is it possible to connect an RCD without grounding?

Yes, the RCD works without grounding, but does not provide 100% protection. For example, if a phase penetrates the machine body, the RCD will only trigger when a person touches it. Better to combine with circuit breaker.

❓ Which RCD should I choose for a welding machine?

For transformer welder - selective RCD 100mA with delay (for example, Hager CD440S). For inverter - the usual is enough 30mA, but with a current reserve (for example, Legrand DX³ 50A 30mA).

❓ Why does the RCD work for no apparent reason?

Reasons:

  • 🔌 Leak in an old extension cord or tool.
  • 💧 Humidity in the shield (condensation).
  • ⚡ Insulation breakdown in hidden wiring.

Solution: Disable all consumers and check one by one every line.

❓ Is it possible to install one RCD on several garages?

No, it's gross violation of the PUE. Every garage should have personal protection. An exception is if garages are connected via one common RCD 300mA (fire protection) + individual 30mA in every box.