Terminal and Distribution Blocks

Where terminal blocks sit in a panel

A terminal block is the defined point where one conductor ends and the next begins. Putting that point in a block rather than in a joint makes the connection testable, disconnectable and repeatable — which is why the terminal rail is usually the first thing an electrician looks for when tracing a fault.

The three series

• DTBA universal terminal blocks — the general-purpose series for connecting and distributing conductors on a DIN rail.
• DTDB distribution blocks — for splitting one incoming conductor into several outgoing circuits at a single point.
• DTBB main branch terminal blocks — the heavy end of the range, with a triple-coated brass body for main and branch connections.

Conductors and range

The range covers cross-sections from 50 to 240 mm² at the main-branch end, and the DTBB series accepts both copper and aluminium conductors — which matters on incoming supply cables, where aluminium is common and a copper-only block would force a transition joint. The blocks mount on standard DIN rail and follow IEC 60947-7-1.

Selecting a block

• Function — DTBA to connect, DTDB to distribute, DTBB for main and branch connections.
• Cross-section — match the block to the largest conductor it will clamp, not to the average.
• Conductor material — check aluminium compatibility before specifying a block for an incoming supply cable.