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UL certification

PCB terminal blocks and PCB connectors with UL certification

UL certification

Certifications such as UL or CUL often raise questions with device developers. As a responsible manufacturer of device connection technology, Phoenix Contact develops and tests products so that customers can obtain international approval for their devices. 

PCB terminal blocks and PCB connectors are recognized as individual components by UL (UL 1059). In the end application, components undergo final evaluation and are approved for operation together with the device (UL 508 (C) and UL 840). 

For safety reasons and for each UL certification, it is imperative that the required air clearances and creepage distances are adhered to. The clearance is the shortest path through the air that current between two conductive parts can travel. The creepage distance is the shortest path along the surface of an insulation material that current can travel between two conductive parts.

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Product standards

UL 1059: terminal blocks

In order that Phoenix Contact products can be used in industrial and semi-industrial applications without restriction, we generally test them according to UL 1059. The following table lists the air clearances and creepage distances required for the components. The Use Group refers to the subsequent area of application of the terminal device.

Use GroupDefinitionMax. nominal voltage (V)Clearance (mm)Creepage distance (mm)
AOperating elements, consoles, etc.

150

300

600

12.7

19.1

25.4

19.1

31.8

50.8

BStandard devices, including office and electronic data
processing equipment, etc.

150

300

600

1.6

2.4

9.5

1.6

2.4

12.7

CIndustrial applications, without restrictions

150

300

600

3.2

6.4

9.5

6.4

9.5

12.7

DIndustrial applications, operating equipment with limited rating

300

600

1.6

4.8

3.2

9.5

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Device standards

UL 508: industrial control equipment
Terminal blocks that are recognized according to UL 1059, meet the requirements of UL 508 for field wiring terminal blocks. They can therefore be used without restriction in devices according to this standard. UL 508 also permits alternative rating according to UL 840.

UL 508 C: power conversion equipment
This UL standard applies specifically to power electronics (motor controls, frequency inverters, etc.). The requirements for field wiring terminal blocks are similar to the specifications of UL 508. Alternative rating in accordance with UL 840 is also possible here.

UL 840: insulation coordination including clearances and creepage distances for electrical equipment
This standard describes an alternative procedure for designing the insulation of end products for defined ambient conditions (overvoltage category, pollution degree, material index), provided that this is permitted by the device standard.

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In accordance with UL 840 (3rd edition 2005), the following procedures are carried out to determine air clearances and creepage distances:

  1. Equivalent clearances
    Not meeting the clearance required in the device standard is permitted if the termination device has passed one of the surge voltage tests described in UL 840 (Table 7.1*) without sparkover. The amount of surge voltage depends on the clearance required in the product standard.
  2. Clearances for limited surge voltages
    If it is ensured that surge voltages occurring during operation do not exceed a specified maximum value, the required clearances for the known pollution degree can also be determined in accordance with Table 8.1*.
  3. Creepage distances
    The minimum requirements described in Table 9.1* for general creepage distances and those specifically for PCBs must be met, taking into consideration the operating voltage, pollution degree, and resistance to creepage of the material..

* Tables in accordance with UL 840 standard


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Further information
Certification and approval

PHOENIX CONTACT (Pty) Ltd.

36 Lyn Road
P.O. Box 916
ZA-Ferndale 2160
+27/11/801-8200

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