Complete Electrical Installation Design for a Two-Storey Residence
Project Overview
This project involved the complete electrical study of a real two-storey residential building — my own vacation house — rather than using the standard floor plan provided in the course. The study was conducted as part of the "Electrical Installation Design" course at the Technical University of Crete, School of ECE, during the Spring 2024–2025 semester, under the supervision of Prof. Georgios Peppas.
The design covers all aspects of a residential electrical installation: floor plan layouts for both the ground floor and first floor created using panelCAD (TiSoft), hand-drawn single-line diagrams for three distribution panels compliant with current regulations, full load analysis and phase balancing across a three-phase supply, cable sizing and protection coordination (MCBs, RCDs, isolators), voltage drop verification, and a lightning risk assessment assuming the building is located in Orestiada (50 thunderstorm days/year).
Distribution Panels
3 Panels (1 Main + 2 Sub)
Central panel UC1 at ground floor, sub-panel UC2 at first floor, external sub-panel UC3 for outdoor loads.
Total Circuits
20 Individual Circuits
Including lighting, outlets, HVAC, water heater, EV charger, dishwasher, oven, and three-phase motor for gate.
Supply
Three-Phase 400V / 63A
Balanced load distribution across L1, L2, L3 with total currents of 72.7A, 76.9A, and 75.2A respectively.
Voltage Drop
All Lines < 5% (11.5V)
Maximum recorded voltage drop: 1.5V (dishwasher line). All lines well within the 5% regulatory limit.
Methodology & Design Decisions
The load distribution was carefully balanced across three phases to minimize neutral current. Each circuit was individually sized with appropriate MCB type (B for lighting, C for power outlets and motors), cable cross-sections ranging from 1.5mm² to 6mm² depending on load current, and conduit diameters from 16mm to 32mm.
Design Note:
Special attention was given to the EV charger circuit (21.74A, three-phase, 6mm² cable with dedicated 25A MCB and 32A isolator) and the external gate motor circuit (three-phase with dedicated 10mA RCBO for safety, as the gate has a manual override mechanism).
The lightning risk assessment yielded a CRL value of 5,666.7 — well above the 1,000 threshold, meaning SPD protection is not mandatory. However, SPD devices were included in both the main panel and external sub-panel for additional protection of sensitive electronics.
Panel Load Summary
| Panel | Circuits | L1 (A) | L2 (A) | L3 (A) |
|---|---|---|---|---|
| UC1 (Main — Ground) | 8 | 72.71 | 76.94 | 75.22 |
| UC2 (Sub — First Floor) | 8 | 30.68 | 33.81 | 31.59 |
| UC3 (Sub — External) | 4 | 26.13 | 30.13 | 23.63 |