If, when installing an electrical panel, you find that two or more wires need to be connected to one circuit breaker, it is important to do this without violating the rules of the Electrical Installation Code and without the risk of contact overheating. The most common mistake is twisting several wires under one terminal of the machine, which leads to loose contact, heating and even a fire. The correct solution depends on the type of machine, wire cross-section and connection diagram (for example, phase distribution or parallel supply several lines).
In this article, we will analyze the acceptable connection methods (via terminal blocks, sleeves, buses), calculate the maximum number of wires for 16A, 25A and 40A machines, and also show how to avoid common mistakes when working with ABB S200, Legrand TX3 and other popular series. Let us separately dwell on cases where connecting several cables to one machine strictly prohibited - for example, when protecting powerful consumers (electric stoves, boilers) or in circuits with high starting currents.
Why can't you just twist the wires and put them under the terminal of the machine?
The main problem of twisting several wires under one terminal of the machine is uneven current distribution. Even if the wires are securely tightened, over time the contact weakens due to temperature expansion, and the current begins to “flow” mainly through one core. This leads to:
- 🔥 Local overheating - the temperature at the point of contact can exceed 100°C, which will melt the insulation and body of the machine.
- ⚡ Sparkling — when the contact weakens, micro-arcs occur that destroy the metal of the terminal.
- 🛑 False positives - the machine may turn off due to heating of the bimetallic plate, and not due to real overload.
The second reason is non-compliance with standards. According to the PUE (clause 2.1.21), each conductor must be connected to a separate terminal. The exception is special terminals certified for group connection (for example, Wago 222 with pasta). However, even they have restrictions on the cross-section and number of cores.
⚠️ Attention: Slot machines IEK BA47 and EKF PROxima have thin brass terminals that become deformed when multiple wires are tightened. They absolutely cannot be used for group connection without transition elements.
Acceptable ways to connect several wires to one machine
There are four proven methods that comply with regulations and ensure reliable contact:
- Terminal blocks (for example, Wago 221 or Phoenix Contact) - allow you to combine several wires into one point, and then connect it to the machine. Suitable for sections up to 4 mm².
- Sleeves for crimping (GML, GSI) - used to connect wires of the same cross-section. After crimping, the sleeve is insulated with heat shrink and connected to the machine as a single conductor.
- Bus splitters (for example, Legrand 408114) - metal tires with several holes for wires. They are installed on a DIN rail and connected to the machine with a jumper.
- Adapter terminals (for example, ABB SAM) - special modules for group connection, certified to work with machines.
The choice of method depends on:
- 🔧 Wire sizes — the sleeves are suitable for large sections (6–10 mm²), and Wago terminals are suitable for small sections (1.5–2.5 mm²).
- 📏 Number of wires - tires can withstand up to 8-10 cores, and sleeves - usually 2-4.
- 💰 Budget — Wago terminals are cheaper than tires, but require regular checking of tightness.
How many wires can be connected to a 16A, 25A and 40A circuit breaker?
The maximum number of wires depends on rated current of the machine and core sections. Below is a table for copper wires (PV-3, VVGng) at an ambient temperature of 25°C:
| Machine denomination | Wire cross-section, mm² | Max. number of wires | Max. total current, A |
|---|---|---|---|
| 16A | 1,5 | 3 | 15,2 |
| 16A | 2,5 | 2 | 15,8 |
| 25A | 2,5 | 3 | 24,5 |
| 25A | 4,0 | 2 | 24,8 |
| 40A | 6,0 | 2 | 39,6 |
Notes:
- 📌 For slot machines Schneider Electric Acti9 It is allowed to connect 4 wires with a cross-section of 1.5 mm² to a 16A circuit breaker (when using a bus splitter).
- 📌 If the wires are of different sections, be guided by minimum section in the group.
- 📌 For aluminum wires (AVVG) reduce the number of cores by 20–30% due to lower current conductivity.
⚠️ Attention: Exceeding the specified values leads to overheating of the machine terminal. For example, connecting 4 2.5 mm² wires to a 16A circuit breaker will cause heating to 70–80°C even with a 12A load.
Step-by-step instructions: connecting via terminal block
Let's consider the most universal method - using a terminal block Wago 222-413 for connecting three 2.5 mm² wires to the machine ABB S201 C16.
Screwdriver with voltage indicator
Terminal block Wago 222-413 (3 wires)
Jumper made of PV-3 wire 2.5 mm² (length 10 cm)
Insulating Heat Shrink (Optional)
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Step 1: Turn off the power
Check that there is no voltage at the input circuit breaker using an indicator screwdriver or a multimeter. If the panel is live, turn off the input switch.
Step 2: Prepare the Wires
Strip the insulation to 10–12 mm (for Wago) or 15 mm (for sleeves). There is no need to twist the wires - the terminal will ensure reliable contact without twisting.
Step 3: Connect the wires to the terminal
Insert the stripped ends into the terminal holes Wago 222 until it clicks. Make sure that all the wires are inserted all the way. If you are using a sleeve, crimp it with press pliers. PK-16.
Step 4. Connect the terminal to the circuit breaker
Cut the jumper from the PV-3 wire and strip both ends. Insert one end into the free hole of the terminal, the other into the terminal of the machine. Tighten the machine screw to a torque of 0.8 Nm (for ABB S200).
Step 5: Check the connection is secure
Pull each wire lightly - it should not come out of the terminal. If you use a sleeve, check the circuit with a multimeter in continuity mode.
For slot machines Legrand DX3 use terminals with spring-type terminals (e.g. Wago 2273). They hold aluminum wires better and withstand vibrations.
Common mistakes and how to avoid them
Even experienced electricians make mistakes when making group connections. Here are the most common:
- ❌ Using twists instead of terminals - leads to weakening of contact after 1–2 years. Solution: Always use certified connectors.
- ❌ Connecting wires of different sections without adapters - thin wires overheat. Solution: use sleeves with a transition (for example, GML-10 for connecting 4 mm² and 6 mm²).
- ❌ Tightening the machine screw with a force of more than 1 Nm - deforms the terminal. Solution: use a torque screwdriver.
- ❌ Ignoring Color Coding — phase wires (L) should be brown/black, neutral wires (N) should be blue. Solution: Label the wires with heat shrink tubing.
Another critical error - connecting the PE conductor (ground) to the machine. Grounding must go directly to the PE bus, bypassing any switching devices. An exception is RCDs and differential circuit breakers, where PE is connected to a separate terminal.
What should I do if the machine heats up after connecting several wires?
1. Disconnect the load and check the terminal temperature after 10 minutes. If it is hot, the problem is in contact.
2. Recheck the tightness of the screws (for automatic IEK the torque should be 0.6–0.8 Nm).
3. Disassemble the connection and inspect the wires for melting. If necessary, cut off the damaged area and repeat the connection through a new terminal.
4. If heating is repeated, reduce the number of wires or increase the cross-section.
When connecting several wires to one machine is prohibited
There are cases when group installation is unacceptable even using terminals:
- 🔌 Power supply circuits for powerful consumers (electric stoves, boilers, air conditioners) - require a separate machine.
- ⚡ Lines with high inrush currents (compressors, pumps) - the group contact may not withstand the current surge.
- 🏠 Introductory machines (up to 63A) - connecting several cables to them violates the selectivity of protection.
- 🔥 Premises with increased fire hazard (baths, wooden houses) - require double redundancy of contacts.
In these cases use:
- 🔹 Individual machines for each line.
- 🔹 Distribution blocks (for example, ABB OT40F3) to share the load.
- 🔹 Contactors for managing powerful consumers.
Connecting several wires to one machine is only permissible for lighting or socket groups with a total load of no more than 70% of the machine’s nominal value. This solution is not safe for power lines.
Frequently asked questions about connection
Is it possible to connect 4 wires of 1.5 mm² to a 16A circuit breaker?
Theoretically yes, but only through a bus splitter (for example, Legrand 408114) and provided that the total load does not exceed 12A. For reliability, it is better to limit yourself to 3 wires or use a 20A machine.
Which terminal block is better: Wago or Phoenix Contact?
Wago 222 more convenient for installation (screwless clamps), but Phoenix Contact withstands high currents and vibrations. For car guards (for example, in campers) it is better Phoenix, for home electrical wiring - Wago.
Do I need to solder the wires before connecting to the machine?
No, soldering is not recommended - the solder “floats” over time and weakens the contact. It is better to use crimp sleeves or spring terminals.
Is it possible to connect aluminum and copper wires together?
Only through special terminals with anti-oxidation paste (for example, Wago 2273 with Alu-Plus). Direct contact between copper and aluminum leads to galvanic corrosion.
How to check the connection quality after installation?
Use a thermal imager or pyrometer to measure the terminal temperature under load. The norm is no more than 40°C at 80% of the rated current. Also check for sparking in the dark.