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TPN 3-Phase Distribution Boards Explained

Distribution Boards

TPN 3-Phase Distribution Boards Explained

TPN (Triple Pole and Neutral) distribution boards are built for three-phase supplies. They spread load across three phases, take both three-pole and single-pole devices, and suit 11–22kW EV charging, commercial premises and any site fed from a three-phase incomer.

Quick answer

A TPN board carries L1, L2, L3 and neutral on its busbar, so one board can feed three-phase loads (such as a 22kW charger) and single-phase circuits together. It needs a three-phase supply.

What TPN means

TPN stands for Triple Pole and Neutral. The busbar carries all three phases and a neutral, so both 3-pole devices (three-phase loads) and single-pole devices (one phase and neutral) can go in the same board.

That flexibility is the main advantage in a mixed installation: a 22kW three-phase EV charger on a 3-pole MCB, alongside single-phase lighting and socket circuits on individual RCBOs, all from one board.

As three-phase EV charging, solar and battery systems become more common, TPN boards have moved from a specialist commercial product to something many installers meet regularly.

TPN board vs single-phase consumer unit

Feature Single-phase consumer unit TPN 3-phase board
Supply 230V (L + N) 400V three-phase (L1 + L2 + L3 + N)
Busbar phases 1 3, balanced across the ways
3-pole device support No Yes
Single-pole device support Yes Yes
Load distribution Limited to one phase Can be spread across all three phases
Typical applications Domestic, small commercial Three-phase EV charging, commercial premises, light industrial

WCED WTPN series

The WTPN range is a 1.2mm steel three-phase board to BS EN 61439-3, for commercial, industrial and high-demand domestic EV installations. It has a 125A 4-pole main switch and a Type 2 surge protection device as standard, and comes in a range of way counts from 4 to 24. You populate it with the MCBs and RCBOs your circuits need.

  • 125A 4-pole main switch as standard
  • Type 2 SPD fitted as standard
  • 4 to 24 way options
  • Solid copper busbar for low-impedance connections
  • Accepts 3-pole and single-pole devices
  • Extension boards and spreader boxes to expand later

For commercial projects, see 3-phase distribution boards for commercial work.

Sizing a board for EV charging

Charger type Charger output Current per phase Board and protection
Single-phase 7kW 7kW (32A) 32A on one phase Single-phase board, 32A RCBO
Three-phase 11kW 11kW (16A per phase) 16A × 3 phases TPN board, 3-pole 20A MCB, plus Type B RCD where the charger has no DC leakage detection
Three-phase 22kW 22kW (32A per phase) 32A × 3 phases TPN board, 3-pole 40A MCB, plus Type B RCD where the charger has no DC leakage detection

Whether you need a Type B device depends on whether the charger has its own DC leakage protection. See What is a Type B RCD?

Shop WCED TPN 3-phase distribution boards

TPN boards with 125A 4-pole main switch and Type 2 SPD, ready to populate. In stock.

View TPN boards

Frequently asked questions

Can I install a TPN board on a single-phase supply?

No. A TPN board needs a three-phase supply. On a single-phase supply two of the three busbars would be dead and any 3-pole device would not work correctly. For a single-phase EV sub-board, use a single-phase consumer unit or EV connection unit.

How do I balance the load across three phases?

Spread single-phase circuits as evenly as you can across L1, L2 and L3, roughly equal numbers on each. That minimises neutral current and stops one phase being overloaded while the others sit idle. Many boards label the ways by phase to make this easy.

Do I need a three-phase supply from my DNO for a 22kW EV charger?

Yes. A 22kW charger needs three-phase. That normally means a new supply application to your DNO, who assess whether the network can support the extra load and quote for the connection. Lead times vary but are typically 4 to 12 weeks.

Distribution Boards3-Phase and Multi-Charger EV InstallsRCDs & RCBOs4-Pole vs 2-Pole RCDs for 3-PhaseRCDs & RCBOsWhat Is a Type B RCD?Commercial & Trade3-Phase Boards for Commercial Projects

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