Electrical Panel for a House: Assembly, Components, and Turnkey Installation

The electrical panel is the heart of a house's electrical system. It houses all protective devices, group distribution, control, and automation. The reliability of the entire electrical system depends on the quality of the panel assembly: fire safety, ease of maintenance, and future expansion possibilities. A poorly assembled panel is not just an inconvenience. It's a risk of fire, electric shock, and damage to expensive equipment. In this guide, we will thoroughly cover everything from choosing the enclosure to final labeling, with real-world examples and common mistakes.

Why an Electrical Panel is Needed and What It Does

An electrical distribution panel is the point where electricity from the grid is distributed to individual groups (circuits) and protected from emergency situations. Each group serves a specific part of the house or a particular high-power appliance. This division offers several key advantages.

Firstly, selective disconnection. If a circuit breaker trips on the bathroom line, the rest of the house continues to work. You find and fix the problem without sitting in the dark. Secondly, overload protection. Every cable has its permissible power rating. The circuit breaker disconnects the line before the cable overheats and the insulation catches fire. Thirdly, protection against electric shock. An RCD (residual current device) instantly breaks the circuit if current flows through a person or damaged insulation. Fourthly, protection of equipment from overvoltages. Voltage relays and SPDs protect sensitive equipment from voltage surges in the network.

A modern electrical panel is not just a row of circuit breakers. It is an engineering system that includes dozens of components and requires careful design before assembly.

Panel Enclosure: Flush-Mounted or Surface-Mounted

Flush-mounted (internal) — installed in a wall niche. It looks neat and does not protrude beyond the wall surface. A niche needs to be cut during renovation, so this option is chosen for major apartment or house renovations. The depth of the niche depends on the enclosure: usually 100–120 mm. For concrete walls, a hammer drill with a core bit and chisel is needed; for brick walls, it's simpler. In plasterboard partitions, special enclosures with mounting to the sheet are used.

Surface-mounted (external) — attached to the wall surface. Easier installation, can be installed without renovation. Suitable for garages, temporary solutions, wooden and frame houses (where cutting a niche is not possible or undesirable). Protrudes 100–150 mm from the wall. For outdoor conditions (entrance panel on the facade or pole), a surface-mounted enclosure with increased moisture protection is chosen.

Enclosure material: metal or plastic. Metal panels (steel with powder coating) are used for large assemblies of 72 modules or more, industrial facilities, and basements. They provide better protection against mechanical damage and have a higher fire resistance class. Plastic enclosures are standard for household panels up to 72 modules. They are lighter, cheaper, and do not conduct electricity, which provides additional protection.

Enclosure brands: ABB Mistral (AT series for flush-mounted, WT for surface-mounted) — premium, reliable hinges and locks, convenient access to DIN rails. Schneider Pragma — durable plastic, tight-fitting door. Schneider Kaedra — for wet and outdoor conditions (IP65). Hager Volta and Golf — good quality, convenient internal layout. IEK ЩРн — budget option, thinner plastic, less convenient fasteners.

IP protection class: IP30 — for dry rooms (standard for flush-mounted). IP44 — for bathrooms and semi-enclosed spaces. IP55 and higher — for outdoors, basements, technical rooms. IP65 — full protection against dust and water jets (external input panel).

How Many Modules Are Needed

One module is the width of a single-pole circuit breaker (17.5 mm). A double-pole circuit breaker or RCBO occupies 2 modules. An RCD — 2 or 4 modules (depending on phases). A voltage relay — 1–3 modules. An SPD — 2–4 modules. A meter (if internal) — 4–8 modules.

Calculation formula: count all panel components by the number of modules, then add a 20–30% reserve for the future. In a few years, you might add an air conditioner, boiler, underfloor heating, electric vehicle charger — and you will need free spaces in the panel. Reassembling a panel is expensive and complicated.

Approximate sizes: 1–2 room apartment — 24 modules (1 row). 3-room apartment — 36–48 modules (2–3 rows). Private house 100–150 m² — 48–72 modules. Large house with automation, solar station, backup power — 72–120 modules (sometimes two panels).

Components: What Should Be in the Panel

Input Group

Main circuit breaker — the main circuit breaker that disconnects the entire house. The rating depends on the permitted power (specified in the technical conditions from DTEK or the regional power company). Typical values: 32A for an apartment (7 kW), 40A (8.8 kW), 50A (11 kW), 63A (14 kW) for a house. For three-phase connection — a three-phase circuit breaker of the appropriate rating.

Voltage relay — protection against overvoltage and undervoltage. In case of a substation accident or neutral break, the voltage can rise to 300–380V. Without a voltage relay, all equipment in the house will burn out in seconds. The relay disconnects power when the voltage goes beyond the set limits (usually 170–250V) and automatically switches it back on after a configured time (3–10 minutes) once normalized. Popular brands: Zubr D (D32t, D40t, D63t series) — excellent functionality for a reasonable price, made in Ukraine. DigiTOP — a more budget-friendly option. RBUZ — good price/quality ratio. Volt Control by Novatek — industrial series.

SPD (Surge Protective Device) Class II — protection against lightning and switching impulses. Installed after the main circuit breaker. A mandatory condition is the presence of grounding, otherwise the SPD will not work. It is recommended to install a special fuse or circuit breaker before the SPD, which will disconnect the line if the SPD varistor burns out (there is a status indicator on the housing).

Fire-protective RCD 100–300 mA at the input — disconnects in case of a serious leakage current due to damaged insulation in the wall. This is not protection against electric shock to a person (for this, 30 mA is needed), but protection against fire. If a cable in the wall is abraded somewhere and current flows through wet plaster, the fire-protective RCD will disconnect the line before the leakage point heats up to ignition.

Meter — can be external (on a pole or in a floor distribution board) or internal (in a home distribution board). If internal, it occupies 4–8 modules. Modern meters often have remote data transmission modules.

Group RCDs

After the main input group, there are group RCDs, each serving several lines. Principle: one 40A/30mA RCD for 3–5 circuit breakers. It is not recommended to connect more than 5–6 lines to one RCD — in case of a leakage in one line, all will be disconnected.

Types by differential current: 30 mA — standard for all household lines. 10 mA — for wet rooms (bathroom, sauna, swimming pool). Types by leakage current waveform: AC type — only alternating sinusoidal (basic). Type A — alternating + pulsating DC (mandatory for lines with a washing machine, induction hob, solar inverter, electric vehicle charger). For a house, the minimum is Type A for main groups.

Group Circuit Breakers

Each line — a separate circuit breaker. This is the golden rule. You cannot "combine" several rooms on one circuit breaker, although it is cheaper. Typical configuration for a 3-room apartment:

Kitchen sockets — C16 (cable VVGng 3×2.5). Living room sockets — C16. Bedroom sockets — C16. Children's room sockets — C16. Corridor + hallway sockets — C16. Kitchen + corridor lighting — B10 (cable VVGng 3×1.5). Living room + bedroom lighting — B10. Children's room + bathroom lighting — B10. Boiler — C16 or C20 (cable 3×2.5, separate line). Washing machine — C16 (separate line). Dishwasher — C16 (separate line). Living room air conditioner — C16 (separate line). Bedroom air conditioner — C16 (separate line). Electric stove/oven — C32 (cable 3×6, separate line). Underfloor heating (if any) — C16 (separate line). Total: 15–18 circuit breakers + 4–5 RCDs + input group = 30–40 modules.

For a private house, the following are added: outdoor lighting, garage, workshop, pumping station, electric boiler, gates, video surveillance, server cabinet — and the distribution board easily grows to 48–72 modules.

Busbars and Connections

Neutral busbars N — separate for each RCD. This is a critically important point where even experienced electricians make mistakes. After the RCD, the neutral conductor of each line must go to a busbar that is connected ONLY to this specific RCD. If neutral conductors from different RCDs are connected to each other, false tripping will occur because currents from different lines "mix" and the RCD sees a difference between the phase and neutral conductors.

PE busbar — one common for the entire distribution board, connected to the grounding circuit. All grounding conductors from all lines are connected to it. The PE busbar must not have breaks — it is a continuous conductor from the grounding circuit to each socket.

Phase busbars (connecting busbars) — for connecting several circuit breakers to one RCD. Instead of making jumpers with wires (unreliable, bulky), a copper busbar is used, which is inserted from above into the circuit breaker contacts. Busbars come in single-phase (Pin or Fork) and three-phase versions.

Wires in the distribution board — PV-3 (PuGV) — flexible copper wire in insulation. Cross-sections: 6–10 mm² for connecting the main circuit breaker, 4 mm² for connecting RCDs to circuit breakers, 2.5 mm² for group lines 16A, 1.5 mm² for lighting lines 10A. All connections are made with crimped ferrules (NShVI) — bare copper wire in a circuit breaker terminal oxidizes and loosens over time, leading to heating and fire.

Single-phase vs Three-phase Distribution Board

Single-phase (220V) — standard for most apartments and small houses. One phase conductor (L), neutral (N), and protective (PE) come into the house. Maximum power is limited by the rating of the main circuit breaker: 32A × 220V = 7,040 W, 40A = 8,800 W. This is sufficient for an apartment with a gas stove, but may be insufficient for a house with an electric boiler.

Three-phase (380V) — three phase conductors (L1, L2, L3), neutral (N), and protective (PE). Power is significantly higher: 3 × 32A × 220V = 21,120 W. Three-phase connection is required for: electric boilers with power from 6 kW, electric stoves with three-phase connection, welding equipment, hybrid inverters for solar power stations, electric vehicle charging stations, powerful motors (pump, compressor).

Even phase load distribution — a key rule for a three-phase distribution board. All single-phase consumers are distributed among the three phases as evenly as possible. If the entire kitchen is connected to one phase, and only corridor lighting to another, an imbalance will occur. Consequences: voltage on the underloaded phase increases (to 250V and above), on the overloaded phase it drops (to 190V and below). This shortens the lifespan of appliances and can cause them to fail. A voltage relay for each phase is mandatory.

Assembly Order: Step-by-Step Instructions

Step 1. Single-line diagram design. Before purchasing components, create a complete diagram. It should include: all lines with names (kitchen sockets, bathroom lighting, etc.), cable cross-sections for each line, circuit breaker ratings, RCD grouping, and the main incoming group (circuit breaker, voltage relay, SPD, fire-protection RCD). A single-line diagram is a document used to assemble the electrical panel and allows an electrician to understand the connections 10 years later.

Step 2. Enclosure selection. Count the total number of modules according to the diagram and add a 20–30% reserve. It's better to have an electrical panel one row larger than a cramped one where wires are tightly pressed and there's no space for additional lines.

Step 3. DIN rail and component installation. Arrange components according to the diagram. The standard top-to-bottom order is: main circuit breaker → SPD → fire-protection RCD → voltage relay → group RCDs → circuit breakers. Each DIN rail row usually corresponds to one RCD group with its circuit breakers. Leave a gap of 1–2 modules between groups for convenience.

Step 4. Phase busbar connection. The busbar connects the RCD's phase output to the inputs of the circuit breakers served by that RCD. Ensure the busbar is firmly seated in the terminals. Use end caps on the busbar ends to prevent accidental contact.

Step 5. Neutral busbar connection. Each RCD requires its own neutral busbar. This is the most important rule; violating it leads to nuisance tripping. The neutral busbar is mounted next to its corresponding group of circuit breakers. From it, neutral wires run to each socket and consumer in that group.

Step 6. PE busbar connection. One busbar for the entire electrical panel. All grounding conductors connect here. The PE busbar is connected to the grounding electrode system with a 10 mm² copper wire.

Step 7. Ferrule crimping. All flexible wires (PV-3/PuGV) must be crimped with NShVI ferrules before insertion into the circuit breaker terminal. A bare copper wire in a screw terminal is a ticking time bomb: copper gradually deforms under pressure, the contact weakens, and it starts to spark and heat up.

Step 8. Labeling. Label each circuit breaker with the line number and name (e.g., "L3 — Kitchen sockets"). Use printed labels or labeling tapes. Hand-written with a marker is acceptable during construction but should be replaced with durable labeling later. Additionally: print the single-line diagram and attach it to the inside of the electrical panel door.

Step 9. Contact tightening. All terminals are tightened with a torque screwdriver to the correct torque (0.8–2.5 Nm depending on the circuit breaker). Overtightening will break the terminal or damage the ferrule. Undertightening will lead to overheating. One month after power is supplied, it is recommended to re-tighten all contacts — the metal deforms slightly under load.

Step 10. Pre-power-up check. Use a multimeter to check: absence of short circuits between L and N on each line (should be infinite resistance). Absence of connection between N and PE (except at the PEN splitting point in TN-C-S). Absence of "foreign" neutrals on busbars (each neutral busbar is only for its own RCD). After power is supplied, check the correctness of the connection using the "Test" button on each RCD.

Common assembly mistakes

Mistake #1: Circuit breaker with a higher rating than the cable allows. The most dangerous mistake. A 25A circuit breaker on a 2.5 mm² cable (cable's permissible current is 21A, circuit breaker should be max 16A). During overload, the cable heats up to the insulation's ignition temperature (70–90°C), but the circuit breaker does not trip because its rating is higher than the actual current. Result: a fire in the wall. Rule: the circuit breaker protects the cable, not the appliance. The circuit breaker's rating is always less than or equal to the cable's permissible current.

Mistake #2: Connecting neutrals of different RCD groups to a single busbar. Leads to nuisance tripping. Currents from different lines "mix," the RCD detects a difference between incoming and outgoing current, and trips. An electrician starts looking for a "leak" that doesn't actually exist. Solution: a separate neutral busbar for each RCD, physically separated and labeled.

Mistake #3: Lack of labeling. After a year, no one remembers which circuit breaker controls what. In an emergency, time is wasted searching for the correct line. In the worst case, the wrong circuit breaker is switched off, and work is performed under voltage.

Mistake #4: RCD without a circuit breaker before it. An RCD does not have short-circuit protection. In a short circuit, a huge current (thousands of amperes) flows through the RCD, and its contacts weld together. After this, the RCD will not trip on a leakage current and will not protect a person. A circuit breaker with a rating equal to or less than the RCD's rating is mandatory before each RCD.

Mistake #5: No spare spaces. The electrical panel is assembled "tightly" — all spaces are occupied. A year later, a line for an air conditioner needs to be added — and there's nowhere to put it. The panel either has to be rewired or an additional one installed. Always leave 20–30% free space.

Mistake #6: Cheap components. An IEK circuit breaker for 80 UAH looks like an ABB circuit breaker for 300 UAH, but has a different contact life (from 4,000 to 10,000 cycles instead of 20,000), a less precise trip unit, and may not trip at the maximum short-circuit current. Saving 5,000 UAH on components for an apartment costing millions is a questionable decision.

Mistake #7: Bare wires without ferrules. A bare copper wire in a screw terminal gradually deforms under screw pressure. The contact weakens, transitional resistance appears, the contact point heats up, and the circuit breaker's plastic melts. All flexible wires must be crimped with NShVI ferrules.

Component brands: comparison

Premium

ABB — Swiss-Swedish concern, manufactured in Germany/Italy. S200 series (circuit breakers) — a benchmark for reliability, 20,000 cycles lifespan, 6 kA breaking capacity. F200 series (RCDs) — Type A, super selective. Circuit breaker C16: from 300 UAH. RCD 40A/30mA Type A: from 1,800 UAH. Mistral enclosures — convenient installation, high-quality fittings.

Schneider Electric — French concern, one of the leaders in electrical engineering. Acti9 iC60N series — circuit breakers with a 20,000 cycles lifespan. iID — RCD series. Circuit breaker C16: from 250 UAH. RCD 40A/30mA: from 1,500 UAH. Pragma enclosures — robust, convenient, good door design.

Mid-range segment

Hager — German brand with factories in Germany and France. NDN series — good quality circuit breakers. Circuit breaker C16: from 200 UAH. Volta and Golf enclosures — among the most convenient on the market due to their quick installation system.

Eaton — Irish-American corporation. PL6 series — good quality at a reasonable price. Circuit breaker C16: from 150 UAH. A popular choice for budget projects with decent quality.

Legrand — French brand. TX3 series — mid-range circuit breakers. Circuit breaker C16: from 180 UAH. Practibox enclosures — a decent option for their price.

Budget

IEK, ASKO — from 80 UAH per circuit breaker. Shorter lifespan (4,000–10,000 cycles), less precise trip unit. For temporary solutions and objects with minimal requirements. Not recommended for residential properties with permanent occupancy.

Assembly example: 3-room apartment

Object: 75 m² apartment, single-phase connection 40A (8.8 kW). Gas stove, 2 kW boiler, washing machine, dishwasher, 2 air conditioners, underfloor heating in the bathroom.

Switchboard components: ABB S202 C40 main circuit breaker (2 modules). Zubr D40t voltage relay (3 modules). ABB OVR T2 surge protective device (2 modules). ABB F202A 40A/100mA fire protection RCD (2 modules). RCD group 1 (kitchen + boiler) ABB F202A 40A/30mA Type A (2 modules). RCD group 2 (rooms) ABB F202A 40A/30mA Type AC (2 modules). RCD group 3 (bathroom + underfloor heating) ABB F202A 25A/10mA Type A (2 modules). 14 ABB S201 circuit breakers (14 modules). 6 free modules (spare). Total: 45 modules — ABB Mistral 54-module enclosure (3 rows of 18).

Estimated cost of components: 12,000–18,000 UAH (ABB). Assembly cost: from 3,000 UAH. On-site installation with connection: from 2,000 UAH. Labeling and protocol: included. Total turnkey: from 17,000–23,000 UAH.

Switchboard maintenance and inspection

A assembled switchboard is not a "set it and forget it" item. Recommended maintenance schedule: 1 month after commissioning — tighten all contacts (metal deforms under load). Annually — visual inspection: check for darkened wires, burning smell, heated areas (can be checked with a thermal imager). Press the "Test" button on each RCD — if it doesn't trip, the RCD is faulty and needs replacement. Every 3–5 years — full inspection with measurements: cable insulation resistance, phase-neutral loop impedance, RCD tripping differential current. Results are recorded in a protocol.

Signs of problems requiring immediate attention: a circuit breaker or RCD frequently trips without an apparent reason. A circuit breaker or wire in the switchboard is warm or hot to the touch. Smell of burning plastic. Darkened wire insulation or melted circuit breaker housing. Sparking or crackling in the switchboard. Any of these signs is a reason to immediately contact an electrician.

Smart home switchboard

If you are planning automation (Loxone, KNX, HDL, Home Assistant), the switchboard requires additional equipment and space. Automation controllers (Loxone Miniserver, KNX actuators) occupy a separate DIN rail or a separate switchboard. Lighting control relays (one channel — 1 module) — for 20 lighting groups, this means 20 additional modules. Blind control modules, contactors for heating, energy consumption measurement modules — all these require space.

A typical solution for a smart home is two adjacent switchboards: a power switchboard (circuit breakers, RCDs) and an automation switchboard (controllers, relays, actuators). Or one large switchboard of 120+ modules with clear zone separation.

Important during design: each lighting group — a separate cable to the switchboard (even if physically close). Each socket that can be controlled by automation — a separate cable. Cables for motion, temperature, humidity sensors — are laid during the rough-in stage. Saving on cables when designing a smart home is the biggest mistake that cannot be corrected later.

Conclusion

The electrical switchboard is not a place for saving money. The safety of your home for decades to come depends on the quality of design, components, and assembly. Three main rules: always start with a single-line diagram, choose an enclosure with spare capacity, and never install a circuit breaker with a higher rating than the cable allows.

SDS assembles turnkey electrical switchboards: from single-line diagram design to on-site installation with labeling, photo report, and measurement protocol. We use ABB, Schneider, Hager. Each switchboard is accompanied by detailed documentation: single-line diagram, equipment specification, measurement protocol. Switchboard assembly price list → | Order a calculation →