UL 1059:2021 PDF Download

The UL 1059:2021 standard provides requirements for assemblies of wiring terminals and supporting blocks used for connecting wiring. It is important to note that compliance with these requirements does not ensure that the terminal block is suitable for use as a component of an end product.

This standard specifically covers terminal blocks rated 1500 volts or less. Additionally, it includes provisions for protective conductor terminal blocks (PCTB) used for making electrical and mechanical connections between conductors or between conductors and a fixing support, such as a mounting rail. PCTBs are not required to be insulated.

The main purpose of these terminal blocks is to provide permanent support and insulation for wire terminations and joints, preventing the risk of fire, electric shock, or injury to individuals. It should be noted that the acceptability of a terminal block in a specific application depends on its suitability for continued use under the prevailing conditions. It may also be necessary to evaluate the terminal block for additional features or performance characteristics not specified in this standard.

While this standard covers a wide range of terminal blocks, it should be noted that terminal blocks employing connecting means not covered by this standard, such as those requiring a special tool for securing conductors to terminals, may need separate investigation.

Finally, it is important to recognize that the UL 1059:2021 standard does not cover field installed power distribution blocks designed for distributing power in buildings to separate units. These power distribution blocks are investigated under a different standard, specifically Subject 1953, Outline of Investigation for Power Distribution Blocks.