North American equipment manufacturers who make products for the domestic market must comply with local regulations that are fundamentally different from European IEC standards. The same applies, of course, to manufacturers from other countries who wish to export equipment to this market. In practice, it is essential that the equipment is UL-certified. Special care must often be taken to comply with the power limitation associated with NEC Class 2/limited energy circuit.
Bihl+Wiedemann’s advanced ASi solutions consisting of ASi-5/ASi-3 gateways and 30 V power supplies are all UL-certified. Further, we offer special NEC Class 2 power supplies and UL-certified power limitation modules which also satisfy NEC Class 2 requirements on limited energy circuits.
Anyone exporting electrical products to North America, or manufacturing them there for the domestic market, must comply with the rules set out in the NEC, among others. For instance, conformity with the safety regulations of the USA and Canada is confirmed by the UL test mark issued by the “Underwriter Laboratories” testing laboratory. References to UL standards are found in the U.S. National Electrical Code (NEC). Many components, such as typical sensors, are certified as Class 2 only, which means that their power supply must not exceed 100 W. This limitation to 100 W must be tested and certified by UL (or a comparable body) in accordance with the standards. Three options are equally available for this purpose:
- Limited energy circuit according to UL/CSA 61010-2-201
- Limited Power Source according to UL/CSA 60950-1
- Class 2 supply source according to NEC, NFPA 70, Clause 725.121 and CEC, Part I, C22.1.
What Does This Imply for the ASi Installation?
Since ASi-connected sensors are mostly only permitted for use in NEC Class 2 circuits (limited energy circuits), care must be taken to ensure that the power limitation is maintained in accordance with the standard. Bihl+Wiedemann offers two options for this: Either a separate NEC Class 2-certified power supply for each ASi circuit or a heavy-duty power supply in combination with a UL-certified power limitation module (see setup recommendations). Our power limitation module was specially developed for ASi-5/ASi-3. An important aspect, which had special attention during the development, was to make sure that communication on ASi would not be negatively affected by the power limitation module.
More than 1 ASi circuit is required and a separate 100 W power supply is to be used for each ASi circuit. Then it is recommended to use a gateway with 2 ASi circuits and integrated decoupling optimized for 2 limited energy circuits.
A common power supply is to be used for 2 ASi circuits (double master). In that case, to create a UL-compliant 100 W limited ASi circuit, it is recommended to use the power limitation module. One advantage of this variant is flexibility: Machines can be built the same way as usual and for the North American market one simply adds the power limitation module. In addition, the power limitation module enables the implementation of large applications with increased current requirements from ASi (see the final setup recommendation).
If a total of 200 W is not sufficient to supply the ASi nodes, it is possible to use one power limitation module per ASi circuit. Thus, the two ASi circuits can each be split into two separate 100 W sections. Up to a total of 400 W is then available for the ASi nodes of the two ASi circuits.