When it comes to assembling an electrical panel - be it in a garage, in a country house or in an apartment - one of the most controversial issues is: how many wires can be connected to one machine without violating the PUE (Electrical Installation Rules). On forums and social networks, electricians argue until they are hoarse: some claim that “one machine - one wire,” others show photos of switchboards with bundles of wires on one terminal. Where is the truth?

The point is that PUE does not give a direct answer in the "maximum 3 wires" style. The norms regulate core cross-section, connection type and load, and not the number of physical conductors. However, there are indirect requirements that help determine the safe limit. In this article we will look at:

  • 🔹 What does it say PUE 7th edition about connecting wires to machines;
  • 🔹 Why “many wires per terminal” is a time bomb;
  • 🔹 How to make branches correctly (and why WAGO does not always save);
  • 🔹 Real connection diagrams for garages, houses and apartments.

Spoiler: if you see a machine gun with five or more wires on one terminal, this is a sure sign that the installation was done by an amateur - and such a connection will sooner or later begin to heat up. But let's take it in order.

PUE and connecting wires to machines: what the law says

The main document that electricians refer to is PUE-7 (Section 2.1.21). It's written there in black and white:

⚠️ Attention: “At each point of connection, branch or connection of wires and cables, a reliable electrical connection must be ensured, as well as protection from mechanical damage and corrosion.”

But where are the specific numbers? There are none. Instead, the PUE refers to:

  • 📜 GOST R 50462-2009 (requirements for low-voltage equipment) - the permissible currents for the terminals are specified there;
  • 📜 GOST 10434-82 (contact electrical connections) - standards of contact resistance;
  • 📜 Technical specifications of machine manufacturers (ABB, Schneider Electric, IEK etc.).

For example, in a passport for a machine gun ABB S201 C16 clearly stated: maximum cross-section of the connected wire is 25 mm², and number of cores - no more than two (if the cross-section of each does not exceed 16 mm²). But this is the manufacturer’s recommendation, not the PUE.

📊 How many wires do you have connected to one machine?
One
Two
Three
Four or more

Why you can’t connect many wires to one machine: physics of the process

The main problem is not the number of wires, but the contact area and clamping force. When you tighten the terminal of a multi-core circuit breaker:

  1. 🔥 Reduces pressure on each wire — some of the cores may dangle, creating microgaps;
  2. 🔥 Transition resistance increases — the connection point begins to heat up;
  3. 🔥 The contact is oxidized — over time, heating increases until melting or fire occurs.

According to EMERCOM of Russia, 30% of fires are caused by faulty electrical wiring occur precisely because of poor contacts in the shields. And most often - in garages and country houses, where the “masters” save money on automatic machines and shove 4-5 wires per terminal.

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If you see traces of melting or blackening on the machine, this is a sign that the contact has already overheated. Such a machine needs to be urgently replaced, even if it is still “working”.

One more nuance: machines are not designed for the total current of all connected wires. For example, if to C16 connect three 2.5 mm² lines (each of which can carry up to 25 A), then with a simultaneous load the current will exceed 16 A, and the machine will start to work - or worse, it will not work due to a burnt contact.

How many wires can be connected to the machine: cross-section table

In order not to guess, we will use the data of manufacturers and PUE. Below - permissible number of wires depending on their cross-section and type of machine:

Wire cross-section, mm² Max. number of wires per terminal Notes
1,5 2 Only if the machine is 10–16 A (for example, B10 or C16)
2,5 2 For machines up to 25 A. With 3 wires - only through a bus or terminal block
4–6 1 A large cross section requires full contact, otherwise there will be heating
10–16 1 Connection only via lugs NSHVI or NKI

Important: if you need to connect three or more wires to one machine, use:

  • 🔌 Distribution bus (comb) — for single-phase automatic machines;
  • 🔌 Terminal blocks WAGO 222 or Phoenix Contact - for branches;
  • 🔌 Tips NSHVI-2 - for crimping two wires into one contact.
What happens if you ignore these rules?

If the permissible number of wires at the terminal of the machine is exceeded, the following will happen over time:

1. Heating the contact to 70–90°C (risk of insulation melting).

2. An increase in contact resistance, which leads to even greater heating.

3. Burning of the machine terminal and wire - in the best case, the machine will start to “knock out” for no reason, in the worst case, an arc and fire will occur.

4. In garages and workshops, where there is dust and vapors of fuel and lubricants, this is especially dangerous - a spark can cause an explosion.

How to correctly connect several wires to one machine: diagrams

If you need to power several lines from one machine (for example, sockets in the garage or lighting in the country), there is three safe ways:

Method 1: Using a comb (shredder)

Suitable for panels with a large number of single-phase circuit breakers. The comb provides:

  • ✅ Uniform current distribution;
  • ✅ Minimum transition resistance;
  • ✅ Clean installation without a “web” of wires.

Example: for slot machines ABB S200 a comb will do PS 1/27.

Method 2: Terminal Blocks (WAGO, Phoenix)

If you need to branch from one machine onto several lines, use:

  • 🔹 WAGO 222-413 — for wires 1.5–4 mm²;
  • 🔹 Phoenix Contact UTS 4 — for sections up to 6 mm²;
  • 🔹 Terminal blocks for DIN rail - if there are a lot of wires.

1. Strip the wires by 10–12 mm

2. Check that the cross-section of all cores is the same

3. Tighten the terminals to 0.8–1.2 Nm (do not overtighten!)

4. Ring the chain after installation

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Method 3: NShVI lugs (for two wires)

If you need to connect two wires into one contact of the machine, use tips NSHVI-2:

  1. Crimp two wires into one lug;
  2. Connect the tip to the machine;
  3. Check the connection is secure (pull the wires).

❌ What not to do:

  • 🚫 Twist the wires under the terminal;
  • 🚫 Use the machine as a “pass-through” (for example, connect the input to the top terminal, and two lines to the bottom);
  • 🚫 Connect aluminum and copper together (even through a terminal block).

Typical mistakes when connecting wires to machines

Even experienced electricians sometimes make mistakes. Here TOP-5 most dangerous:

  1. Connecting wires of different sections - the thick wire will press against the thin one, the contact will weaken;
  2. Using the machine as a “splitter” - for example, when on input C40, and three 2.5 mm² lines are powered from it;
  3. Tightening the terminal "from the heart" — a pinched wire breaks, especially an aluminum one;
  4. Connecting stranded wires without lugs — the veins become fluffy, contact worsens;
  5. Ignoring Color Coding — phase must be on phase, zero on zero (even if “it works that way”).
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The most common mistake is connecting wires to the machine whose total current exceeds its rating. For example, to C16 They connect two 2.5 mm² lines (each withstands 25 A), and then they wonder why it heats up.

Another common mistake is connecting zero to machine. Remember: machines are placed only in phase! Zero must go to the zero bus (N), and grounding - to PE- tire.

Connection features in the garage, country house and apartment

The requirements for the number of wires on the machine depend on the type of room and load.

🏠 Apartment

The following scheme is usually used here:

  • 🔹 There is a separate machine for each room;
  • 🔹 For powerful appliances (washing machine, air conditioner) - separate lines;
  • 🔹 Maximum two wires per machine (for example, sockets + lighting for one room).

🚗 Garage

In the garage, they often skimp on automatic machines, which leads to a fire. Correct approach:

  • 🔹 Separate automatic machine for lighting;
  • 🔹 Separate - for sockets;
  • 🔹 Separate - for a welding post or compressor;
  • 🔹 No spiders from wires - only combs or terminal blocks.
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In the garage, be sure to use machines with increased dust and moisture protection (for example, ABB S200 with IP20 or higher). Dust + spark = fire.

🌳 Cottage / private house

The most common ones found here are:

  • 🔹 Introductory machine (for example, C50);
  • 🔹 Separate machines for floors or areas (kitchen, bathhouse, workshop);
  • 🔹 For a bath or sauna - a machine with RCD (differential).

⚠️ Attention: if you have old aluminum wiring in your dacha, it's impossible connect it directly to the machine - only through adapter terminal blocks (WAGO Alu-Plus or analogues).

What to do if the machine is already overloaded with wires

If you opened the panel and saw that 4–5 wires are connected to one machine, you can't just disconnect them — you need to rebuild the circuit. Here's the step-by-step plan:

  1. Disable the input machine (de-energize the shield);
  2. Label all wires (for example, stickers or marker);
  3. Determine which lines can be divided (eg lighting and sockets);
  4. Install additional machines (if there is no space, use double-tier DIN rails);
  5. Connect the wires through terminal blocks or a comb;
  6. Check contact heating after 1–2 hours of operation under load.

If there is no room in the panel for new machines, consider the following options:

  • 🔧 Install a larger shield;
  • 🔧 Use modular machines (for example, Schneider Electric Multi9 - they already);
  • 🔧 Transfer part of the load to another shield (for example, for a garage or workshop).

FAQ: Frequently asked questions about connecting wires to machines

❓ Is it possible to connect three 2.5 mm² wires to the C25 machine?

❌ No. Even if the machine can withstand 25 A, three wires with a cross-section of 2.5 mm² can pass up to 75 A in total, which is 3 times the nominal value. Use a terminal block or share the load.

❓ Why does the machine heat up if only two wires are connected?

There are several reasons:

  • 🔥 Poor contact (wires not fully tightened);
  • 🔥 Different sections of veins (one presses on the other);
  • 🔥 The terminal is burnt (the machine needs to be replaced).
❓ Is it possible to connect wires of different sections to the machine?

⚠️ Only if you use adapter terminal blocks or NSHVI. Directly is not possible, since the thin wire will not be pressed tightly enough.

❓ How to connect four wires to one machine?

Not directly. Use:

  • 🔌 Distribution bus (comb);
  • 🔌 Terminal block WAGO 222 on DIN rail;
  • 🔌 Additional machine with jumper from the first one.
❓ Which machines are best to use for a garage?

We recommend:

  • 🔹 ABB S200 — reliable, with good contact;
  • 🔹 Schneider Electric Acti9 — resistant to dust;
  • 🔹 IEK KEAZ - a budget option (but check your contacts more often).

⚠️ In the garage necessarily put RCD or automatic machines - due to humidity and metal surfaces, the risk of electric shock is higher.