Wiring 400V, 3-Φ & 230V, 1-Φ Load Circuits in Distribution Board.400/230V Distribution Board Wiring – Old UK Wiring Color Codes.How to Wire a 3-Phase Load in a Distribution Board?.How to Wire a 1-Phase Load in a Distribution Board?.Balanced & Unbalanced Load in the 3-Phase & 1-Phase System.Single Phase & Three Phase Supply in the UK & EU.