Connecting a SIP to an input machine: step-by-step instructions with diagrams and typical errors

Connecting a self-supporting insulated wire (SIP) to an input circuit breaker is a critically important stage of electrical installation in a private house or country house. Not only the stability of the power supply, but also the safety of the entire building depends on the correct execution of this operation. Errors here can result in contact overheating, short circuits, or even fire. In this article we will analyze all the nuances: from the choice of section SIP to the intricacies of connecting to a circuit breaker, taking into account the requirements PUE 7th edition and practical recommendations from experienced electricians.

Many homeowners mistakenly believe that it is enough to simply run the wire into the panel and clamp it into the terminals of the machine. In reality, there are a lot of pitfalls: choosing between SIP-2A and SIP-4, proper stripping of insulation without damaging the cores, taking into account the load at the input and even climatic conditions (for example, frost resistance of insulation in northern regions). We have structured the information so that even a beginner can make the connection without risk to himself or his equipment.

1. Selection of SIP for connection to the input circuit breaker

The first step is to decide on the brand and cross-section of the wire. There is no universal solution here: it all depends on power of connected load, line length and operating conditions. Let's look at the key criteria:

• 🔹 Brand SIP: For overhead lines up to 1 kV they are more often used SIP-2A (with a supporting zero core) or SIP-4 (all cores are of the same cross-section, without a load-bearing element). To enter the house they usually choose SIP-4, since it is easier to install and does not require additional fasteners.
• 🔹 Core cross-section: Minimum cross-section for single-phase input - 16 mm² (up to 15 kW), for three-phase - 25 mm² (up to 40 kW). If the distance from the support to the house exceeds 25 meters, the cross-section is increased by 1 step.
• 🔹 Isolation: In northern regions, give preference to frost-resistant brands with insulation from cross-linked polyethylene, withstands up to −60°C.

Important: if the power of your home exceeds 15 kW, a three-phase input will be required. In this case use SIP-4 4×35 (four cores of 35 mm² each). To accurately calculate the cross section, use the formula:

⚠️ Attention: Not allowed to use SIP-1 to enter the house! Its insulation is not intended for installation on building facades and can be destroyed by exposure to UV radiation.

Power, kW	Single-phase input (220V)	Three-phase input (380V)	Recommended brand of SIP
Up to 10	16 mm²	10 mm²	SIP-4 2×16
10–15	25 mm²	16 mm²	SIP-4 2×25
15–30	—	25 mm²	SIP-4 4×25
30–50	—	35–50 mm²	SIP-4 4×35 or SIP-2A 4×50

2. Requirements of the PUE for connecting self-supporting insulated wires to the machine

Rules for electrical installations (PUE 7.1.21) clearly regulate how the installation of self-supporting insulated wires into the building should be carried out. Highlights:

• 📜 Connection height: Minimum entry height into the house - 2.75 m from ground level. If this is not possible, use protective cover or pipe stand.
• 📜 Protection against mechanical damage: In the area from the support to the shield, the SIP must be protected with corrugation or a metal hose if it is laid over combustible structures (for example, a wooden facade).
• 📜 Grounding: The input panel must have a separate grounding bus connected to the grounding circuit of the house. Grounding conductor cross-section - not less than 10 mm² for copper.

A critically important point: according to PUE 7.1.34, it is prohibited to connect a self-supporting insulated insulated wire directly to a machine without an adapter sleeve or terminal block if the core cross-section exceeds 16 mm². This is due to the fact that the aluminum strands of SIPs “flow” over time under the pressure of the screw terminals, which leads to weakening of the contact and heating. The solution is to use copper tips or GAM sleeves (aluminum-copper sleeves).

⚠️ Attention: If you connect SIP to a circuit breaker with a rating higher than 63A, be sure to use double terminals or a comb splint. A single clamp will not provide reliable contact for currents above 80A.

Also note climatic version machine. For an outdoor shield, choose models with a protection class of at least IP54 (dust- and moisture-proof). Popular series:

• 🔌 ABB S200 — suitable for currents up to 125A, have reinforced terminals for aluminum wires.
• 🔌 Schneider Electric Acti9 — equipped with an operation indication, convenient for diagnostics.
• 🔌 IEK KVA - a budget option, but requires the mandatory use of tips.

3. Step-by-step instructions for connecting SIP to the input circuit breaker

Now let's move on to practice. To work you will need:

• 🛠️ Stripper for removing insulation (for example, Knipex 12 40 200).
• 🛠️ Crimping pliers for ferrules (e.g. HT-351).
• 🛠️ Set of aluminum-copper sleeves GAM or copper tips ON.
• 🛠️ Torque wrench for tightening terminals (tightening torque - 3.5 Nm for automatic machines up to 63A).

Step 1. Preparing SIP for connection

1. Measure the required length of wire with a margin 1.5–2 m for ease of installation.
2. Remove the insulation from the cores 30–40 mmusing a stripper. Don't use a knife! This may damage the conductors.
3. Place aluminum-copper sleeves onto the stripped ends. GAM and crimp them with pliers. Alternative - copper tips ON, but they require soldering or crimping.

Step 2. Connecting to the machine

1. Turn off the power on the line (check the absence of voltage with the indicator!).
2. Insert the prepared wires into the terminals of the machine. For three-phase input, follow the phase order: L1, L2, L3 (usually from left to right).
3. Tighten the terminals with a torque wrench. Over-tightening is just as dangerous as weak contact! The tightening torque for most machines is 3.5 Nm.

Checked for lack of voltage with indicator|

The veins were stripped without damage|

Tips or sleeves used|

The circuit breaker terminals are tightened to the correct torque|

The shield is grounded to the house grounding circuit -->

Step 3: Check the connection

After connecting, run the test:

1. Turn on the machine and measure the voltage at the terminals with a multimeter. Permissible deviation - ±5% of the nominal value (for example, 209–231V for 220V).
2. Check the terminal temperature after 10-15 minutes of operation under load. Heating is higher 40°C indicates poor contact.

4. Common mistakes and how to avoid them

Even experienced electricians sometimes make mistakes when connecting SIP. Here are the most common:

• ❌ Direct aluminum to copper connection: Without adapter sleeves or tips, aluminum oxidizes, contact deteriorates, and heating occurs. The solution is to use GAM sleeves or tinned copper tips.
• ❌ Insufficient terminal tightening: Leads to contact burnout. Always use a torque wrench!
• ❌ Using SIP indoors: SIP is intended for external installation only. Use inside the house VVGng-LS or NYM.
• ❌ Lack of surge protection: Without SPD (surge protection devices) your equipment is vulnerable to lightning.

One of the most insidious mistakes is ignoring thermal expansion of aluminum. When heated, aluminum strands elongate and when cooled, they contract. If you do not leave a reserve of wire (the so-called “wave”), over time the contact will weaken. Optimal stock - 10–15 cm free wire in front of the machine.

⚠️ Attention: Never connect neutral wire (N) SIP to the grounding bus! This is a gross violation of the PUE, leading to electric shock. The neutral and grounding conductors must be separated at the entrance to the panel.

What to do if the SIP overheats at the connection point?

If after connection you notice heating of the terminals of the machine, immediately turn off the power and:

1. Check the tightening torque of the terminals (should be 3.5 Nm).

2. Inspect the wires for oxidation or damage.

3. Replace the aluminum-copper sleeves if they are deformed.

4. If it reheats, replace the machine with a model with reinforced terminals (for example, ABB S200 instead of IEK).

5. Alternative ways to connect SIP to the machine

Classic method with sleeves GAM not always convenient. Let's look at the alternatives:

• 🔧 Terminal blocks Wago 223: Suitable for core cross-sections up to 35 mm². The advantage is quick installation without crimping. However, for the street, choose models with gel filler (for example, Wago 223-415), protecting against corrosion.
• 🔧 Bolt connectors: Cheap solution, but requires regular tightness checks (every 6 months). Suitable for temporary connections.
• 🔧 Copper adapter cables: SIP is connected to a copper cable (VVGng) through the terminal block, and the copper goes to the machine. The downside is additional voltage losses.

For three-phase inputs with high currents (over 100A), it is optimal to use bus disconnectors. They provide reliable contact and allow easy disconnection of power for maintenance. Popular models:

• 🔌 Schneider Electric NSX - up to 160A, with the possibility of installing releases.
• 🔌 Socomec Diris — modular disconnectors for panels.

Connection method	Max. cross-section, mm²	Pros	Cons
GAM sleeves	120	Reliable contact, durability	Requires crimping pliers
Wago terminals	35	Quick installation, no tools required	Current limitation (up to 100A)
Bolt connectors	50	Cheap, universal	Requires regular maintenance

6. Protection of self-supporting insulated wires from breakage and mechanical damage

SIP, despite its strength, is vulnerable to mechanical loads. To avoid broken or damaged insulation:

• 🛡️ Use anchor clamps on the support and facade of the house. For SIP-4 clamps will do SO 253 or CA 150.
• 🛡️ Install the protective cover at the entrance area to the house. For example, corrugation DKS NG or metal hose RZ-TSH.
• 🛡️ Lay SIP with sagging. Optimal sag - 0.5–1 m for every 10 m line. This compensates for thermal expansion.

In regions with strong winds or ice, use additional support clips every 1.5–2 m. It is also recommended to install Surge Limiters (OSL) at the input if the line passes near tall trees.

💡

The main safety rule: after installing the SIP, be sure to check insulation resistance megohmmeter. The norm for a line up to 1 kV is no less 0.5 MOhm.

7. Frequently asked questions about connecting SIP

Is it possible to connect a SIP directly to a machine without sleeves if the cross-section is 16 mm²?

Technically possible, but not recommended. Even with a small cross-section, aluminum “flows” over time under the pressure of the screw, which leads to weakening of the contact. Better to use GAM-16 cartridges or tips NA-16.

Which machine should I choose for inputting SIP 4×35 (three-phase input 15 kW)?

For such a load, a three-pole circuit breaker is suitable. 50A (for example, ABB S203 C50). It is important that the machine is selective (with delay) to avoid false tripping due to inrush currents.

Is it necessary to install an RCD at the input along with the machine?

RCD at the input not necessary, but is recommended for protection against current leakage. Optimal scheme: input machine → meter → RCD 300 mA → group machines. For an outdoor shield, choose an RCD with moisture protection (IP65).

What to do if the SIP is too short and does not reach the machine?

Do not under any circumstances extend SIP by twisting! Use:

1. Connecting sleeves GSI with compression.
2. Terminal blocks Wago 222-415 (for the street).
3. Transition to copper cable through a terminal block in a sealed box.

How often do you need to check the SIP connection to the machine?

Recommended inspection frequency:

• 📅 Once every 6 months — visual inspection for the presence of melting or oxidation.
• 📅 Once every 2 years — checking the tightening of the terminals with a torque wrench.
• 📅 Once every 5 years — measuring the insulation resistance with a megohmmeter.