1. Start with the terminal model and connection point

Record the equipment model, terminal part number and the connection point used by each circuit. A terminal family name or headline maximum cross-section is not enough. Different levels or connection positions on one product may have different limits. Preserve the document revision used to approve the wiring plan.

Then record the cable conductor material, class and nominal cross-section separately. The terminal specification describes an interface; the cable datasheet describes the proposed conductor. Procurement should join those two records through an explicitly approved termination method, rather than assuming that equal area markings guarantee a fit.

2. Compare the correct termination rows

Phoenix Contact UDB 2X25/16 BU, part 3071358, is a trunk line branch terminal. Its data provides a useful reading example, not a recommendation for every control circuit. The table below preserves the two connection levels separately. Values apply only to this model and the specified termination condition.

The same product data instructs users to use ferrules for stranded conductors. Do not interpret the separate “flexible conductor” row as permission to install bare flexible wire. If the table and preparation notes appear unclear for the intended connection, obtain manufacturer clarification before release.

For example, 16 mm² is within the first-level range for a ferrule without a plastic sleeve, but outside the listed range for one with a plastic sleeve. This is a specification comparison, not an instruction to remove a collar or modify an accessory. Select a documented combination.

3. Match the conductor and ferrule

Check conductor material, nominal area and construction against the ferrule manufacturer’s application instructions. IEC conductor class helps identify construction, but does not approve a particular ferrule-terminal combination. Do not assume that every terminal accepts every flexible conductor class.

Use the ferrule part number and dimensions to confirm selection. Plastic collar colors are not a universal size code: Phoenix Contact’s ferrule guidance shows multiple color systems. A color match alone cannot establish the cross-section, sleeve length or compatibility.

A two-wire ferrule is a separate configuration. Confirm both the ferrule’s permitted conductor combination and the terminal’s approval for that connection; two conductors do not become an approved connection merely because their total nominal area matches a single-wire limit.

IEC 60228 conductor classes for control cables

4. Check lengths and available space

Distinguish the metal sleeve length from the overall ferrule length including the collar. Compare the specified strip length, sleeve dimensions and terminal insertion requirements as a set. Do not assume that a ferrule with the correct area but a different sleeve length is interchangeable.

Check that the insulation collar and the insulated conductor can clear the entry and adjacent parts. The assembled conductor must reach the intended contact region according to the terminal instructions. Do not force insertion or cut strands to reduce the bundle size. If dimensions are missing, request the drawing rather than estimating them from a product photograph.

5. Specify crimping and assembly as a matched process

Identify the approved tool, die or adjustment, applicable conductor size and processing instructions. Crimp profile affects the finished envelope; do not prescribe one shape for all terminals. Keep tool setup and sample identification with the approval record.

Review the prepared end for damaged strands, incomplete insertion, sleeve damage and interference, using the relevant manufacturer’s criteria. Carry out any required sample or retention testing under the agreed method. A simple hand pull or a successful insertion is not proof of the complete electrical or mechanical performance.

Apply tightening torque only where specified for that connection technology and exact position. Screw terminals and spring connections do not share one assembly procedure. The connection range also does not replace checks of circuit current, voltage, temperature or the equipment design.

6. Complete the compatibility confirmation sheet

Keep one record per approved combination and connection position. Resolve missing information before bulk procurement. A substitute cable, ferrule, tool or terminal can change the combination even when the nominal cross-section remains unchanged.

Selecting control cable for an existing terminal system? Send the terminal model, approved termination method, conductor requirements and cable quantity. Ask ZION to confirm the relevant cable construction and available technical data before ordering.

Frequently asked questions