24V Overvoltage Protection

UL508A Industrial Control Panel

Overview

In North America, UL approval provides independent 3rd Party certification that a product has been tested by Underwriters Laboratories (UL) or another Nationally Recognized Testing Laboratory (NRTL) and meets all necessary electric code safety requirements as well as industry benchmarks.

On April 13, 2020, UL released a UL508A supplement document titled "REQUIREMENTS FOR COMPONENTS USED IN INDUSTRIAL CONTROL PANELS" that was published with the intent to help control panel builders determine the requirements for components when used in industrial control panels. The document replaces what was Supplement SA in the Second Edition of UL508A, and subsequently Appendix C in the Third Edition of UL508A. It supersedes the previous version of this document dated October 21, 2019.

Remote VFD Control Panel

UL, in the form of the UL inspector, will carefully consider many factors while determining the fitness of the Surge Protective Device (SPD) for the equipment that is being evaluated for UL compliance. It is critically important to understand the process that UL will use to evaluate the SPD according to UL508A.

Each component belongs to an individual Category that describes the specific requirements of the component. In a UL508A Industrial Control Panel, the Surge Protective Device will be evaluated based on Sections 36, 47, and 75. These sections are referenced in Table 1 of the Supplement document.

Table 1 - Components that comply with specific requirements

|Section 47 - Surge control devices meeting component selection requirements|

UL508A Paragraph reference	Component description	UL Standard	Category control number(s)	System & Features	Part #	Link
47.1.3 Surge control devices	Listed isolated Loop Circuit Protectors	UL 497B	QVGQ	2-Wire Replaceable Module	DLA-24D3
				2-Wire Replaceable Module Visual Indicator	DLAS-24D3
				2-Wire Replaceable Module Max. Current 4A	DLAH-24D3
				2-Wire Replaceable Module Faiure Mode - No Line Cut	DLAW-24D3
				2-Wire Replaceable Module Hazardous Locations	DLA-24D3-Ex
				2-Wire 6mm Compact	DLC-24D3
				4-Wire Replaceable Module	DLA2-24D3

Approval Considerations based on UL SPD Type

UL Mark	UL1449 SPD Type	Suitable Ratings	Procedure Described	File Update or Additional Testing	Notes
	1 2	Yes	No	No	The only requirement is that the SPD must match electrical and environmental ratings of the UL 508A Control Panel. A UL field inspection of the control panel with the SPD installed is required as a part of a standard follow-up service visit.
	1CA 2CA 4CA 5	Yes	Yes	Yes	Yes – All UL recognized SPD’s require a UL engineering evaluation of the SPD’s existing UL1449 E–file. This will result, at a minimum, in a cost to update the UL file and may also require testing that would result in additional costs.

CITEL UL LISTED SPD meeting all requirements of UL508A

The following is a list of products for each section. They are UL Listed SPD and require only that they meet the "Suitable Rating" of the control panel. They can be used in all UL locations including,

• Service Equipment Supply Side of Overcurrent Protection
• Service Equipment Load Side of Overcurrent Protection
• Non-Service Equipment Feeder or Branch Circuits
• Isolated Control Circuits

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