Many customers are surprised by the size of their UL control cabinet. They did not expect that the UL control cabinet for a machine or system being exported to the U.S. or Canada would be significantly larger than the control cabinet for the same machine or system in Europe.
Different Standards in the Control Cabinet According to the UL Standard
There are several reasons for the increased space requirements in UL control cabinets, stemming from the different electrical systems and, consequently, the different regulations in Europe and North America. While IEC standards and EU directives apply to control cabinet construction in Europe, the strict UL standards are authoritative in the U.S., and CSA standards in Canada. UL and CSA have reached an agreement to recognize each other’s standards. However, both are far removed from the EU standards. There are significant differences in the regulations governing control cabinet construction.
Main Switch
For control panels ( Industrial Control Panels) installed in ordinary locations (OrdLoc area), the UL 508A standard applies in the United States and Canada. According to this standard, the main switch must lock the control panel. For this reason, it cannot be installed in the control panel door. It must either be connected to the mounting plate via a mechanical interlock linkage or supplemented by an electric door interlock. Both options entail additional costs and require more space compared to the permitted methods in the EU.
Compliance with Clearances and Creepage Distances for Components Used
To protect people—and the equipment itself—from the effects of electrical operating voltages, which can arise quickly—especially during malfunctions—and cause devastating damage, there are precise regulations regarding clearances and creepage distances that must be followed. However, manufacturers of EU control cabinets do not always adhere strictly to these dimensions. Often, the space allocated for clear and creepage distances is too small. In the U.S. and Canada, on the other hand, clear and creepage distances are verified during acceptance testing. If they are too small, the control cabinet will not be approved by the on-site inspectors. For this reason, UL control cabinets often require more space to be allocated for clearances and creepage distances than is available in EU control cabinets.
Separate Installation of Certain Electrical Circuits
According to UL, certain circuits in a UL-compliant control cabinet—such as the power supply cable or a Class 2 circuit—must be routed separately from the other circuits. They must neither intersect nor cross the other circuits. This requirement does not apply to EU control cabinets, which is why the circuits can be arranged in a much more space-efficient manner there.
Protective Components
In special electrical circuits, such as those found in electrical outlets for the North American market, additional protective components are often required to meet the strict UL standard. These are often not required in the EU version.
In addition, the components to be used also differ in terms of the short-circuit withstand capacity (SCCR) required by the operator. These components for the UL control cabinet are often larger than those used in the EU. This, too, requires more space.
Zusammenfassung
It is not possible to make a blanket statement about whether a single UL control cabinet actually requires more space than its European counterpart, as this depends on the specific design. However, since many requirements in the UL standard result in increased space requirements, it is very likely that the UL control cabinet for the same machine or system will be larger than the EU control cabinet.
