UL 60947-7-2: PCB Connection Devices

UL 60947-7-2

UL 60947-7-2 protective conductor terminal blocks

Why a dependable protective connection matters

UL 60947-7-2 addresses protective conductor terminal blocks for copper conductors within the UL 60947 series. Its subject is more specific than joining two wires inside a panel: it concerns a dependable electrical and mechanical connection between a protective conductor and the terminal block’s fixing support. It should therefore not be described as a general feed-through or PCB terminal block standard.

A connection in a grounding circuit must do more than hold a wire in place. It must maintain continuity of the protective path during a fault and meet applicable short-time current conditions. A protective conductor is not intended to carry continuous normal load current; that does not mean it can never carry current.

UL edition and its relationship to IEC

The ULSE record checked on October 17, 2026 identifies the fourth edition dated January 27, 2017, with a latest revision of April 17, 2026. The publisher states that this revision made no technical changes. The UL text adopts the second IEC edition from 2002 with national differences. The editions and differences of IEC 60947-7-2 and the UL adoption must be considered together.

The scope includes industrial applications using screw-type or screwless clamping units for copper conductors. Scope limits such as 1,000 V AC and 1,500 V DC do not establish the rating of every terminal block. The permitted conductor range and application ratings of a product come from its own technical data and applicable approval conditions.

PE and PEN perform different functions

PE identifies a protective conductor; PEN combines protective conductor and neutral functions. Although the IEC scope also includes PEN functions, the published UL national differences do not permit terminal blocks with a PEN function. The IEC scope description cannot therefore be transferred unchanged to a UL application.

The difference between neutral and protective earth directly affects terminal selection. A large conductor capacity or a green/yellow housing does not authorize combining neutral and protective functions. Consider the product function, national differences and installation rules together.

Editor’s note: A terminal block that clips onto a rail does not necessarily make an electrical connection to it. A normal feed-through terminal may be insulated from the rail; a rail-contacting PE terminal uses a suitable metal connection as part of its protective function. Green/yellow identification and a secure mechanical fit do not, by themselves, verify the protective circuit.

The DIN rail is part of the connection system

In a rail-contacting design, the DIN rail provides both mechanical support and part of the electrical protective path. Its profile, material, contact surface and mounting arrangement must match the manufacturer’s specified configuration. Compatibility between the terminal and rail, and the rail’s connection to the panel’s protective bonding system, are separate checks.

Paint, contamination, corrosion or unsuitable accessories can compromise the intended metal contact. Screwing a rail onto a metal mounting plate does not by itself establish a suitable protective path. Evaluate the terminal block, rail, bonding points and protective conductor bar as a system; the terminal block’s catalogue rating alone does not establish compliance of the complete panel.

Selecting conductors and connection methods

The copper conductor size, construction and preparation must suit the selected product. Permitted ranges may differ for solid, stranded, flexible and ferruled conductors. Follow the manufacturer’s specifications for stripping length, tightening torque and the number of conductors permitted in each clamping unit.

Conductor size and ampacity matter, but PE selection cannot be reduced to a normal load-current table. Protective-device disconnection conditions and the thermal effects of fault current also matter. When choosing between spring and screw connections, use the product approval and installation conditions; the connection technology’s name alone is insufficient.

What do the tests evaluate?

Applicable requirements address terminal mounting, clamping-unit mechanical strength, conductor retention and connecting capacity. Electrical assessment focuses on contact continuity, voltage drop and short-time withstand current. Insulation and material tests depend on the product construction and relevant provisions.

Even a small contact resistance matters under fault current. As a calculation example using Ohm’s law, 10 A through a 1 mΩ connection produces a 10 mV voltage drop. This illustrates the relationship; it is neither an acceptance limit from the standard nor a specified field-test current.

Test-lead and probe-contact resistance can affect low-resistance measurements. Where appropriate, a four-wire Kelvin measurement reduces these effects. A multimeter’s continuity beep does not demonstrate compliance with all mechanical and short-time current tests. Product type testing and verification of an installed circuit serve different purposes. Use suitable instruments on a circuit that has been isolated and verified as de-energized.

An example in a motor control panel

The PE conductor of a motor operated by a variable frequency drive can connect through a suitable protective conductor terminal to the panel’s verified protective bonding system. With a rail-contacting product, the rail’s role in that path must also be considered. If a terminal or rail is replaced during maintenance, verify protective continuity again.

Cable shielding or functional earthing must also be distinguished from protection against electric shock. A shield clamp contacting metal for EMC purposes does not automatically qualify as a PE terminal. Evaluate the shielding function and protective conductor function against the product’s declared characteristics.

Read product requirements alongside installation rules

Mentioning a UL standard in a catalogue does not, by itself, establish certification of a particular product. Check the model, certification record, suitable accessories and conditions of use. U.S. projects also require consideration of the NEC; Canadian projects involve the CEC and applicable local acceptance requirements. Terminal block compliance does not establish compliance of the complete panel.