Surge Protection for Hazardous Location Actuator Control Panels (UL508A)

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Today's increased reliance on very sensitive electronics makes surge protection an important topic for Hazardous Location Actuator Control Panels listed to UL508A. The Insurance Institute for Business & Home Safety study found that $26 billion dollars was lost due to non-lightning power surges. In addition, there are about 25 million lightning strikes in the US each year that cause between $650M to $1B in losses according to the Insurance Information Institute, State Farm©.

Selecting SPD for UL508A Hazardous Location Actuator Control Panels

NEC/NFPA 70 require that Surge Protective Devices (SPDs) shall be UL1449 Listed. This means selecting a surge protector is easier than it has ever been. There are only a few choices available for SPDs that are UL Listed for any of the most commonly used surge standards including UL1449 5th Edition, UL497B, and UL497E.

Haz Loc Actuator Control Panel

Recommended SPD for Hazardous Location Actuator Control Panel

LocationEquipmentSystemSurge Protector Model#Link
Distribution Panel120/208V
4W+G, Wye
MS200-120Y MS200-120Y

UL508A Main
Control Panel
AC Power Input
120V 1ph
DS72US-120S/G DS72US-120S/G

Sensor InputLeased Line
DLA2-24D3 DLA-24D3

Stepper Motor120Vac

Actuator Solenoid120Vac
40A Max.

Communication I/ORS232, RS485DLA2-24D3 DLA-24D3

Determining the acceptability of an SPD
for UL 508A Industrial Control Panels and All Other UL Listed Equipment

The UL inspector will first consider the SPD type when determining it’s acceptability for a given application or piece of equipment. This will include UL 508A as well as all other UL Listed equipment. The first level compliance is based on the UL Approval (LISTED or RECOGNIZED) of the SPD or UL SPD Type and it’s Suitable Ratings. This means that it has to meet all safety, performance, environmental and electrical system ratings of the application. If any of these criteria are not fully met, it will require a Procedure Description, a File Update and/or Additional Testing. These actions will require additional costs that may be substantial. For this reason, it is in the interest of the specifier to use UL LISTED SPD’s to eliminate any uncertainty or to make sure the UL RECOGNIZED SPD is selected at the time of UL submittal of the equipment.

Approval Considerations Table based on UL SPD Type

SPD Type
Update or

YesNoNoThe 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.



YesYesYesYes – 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.


1NFPA 70 edition 2020, Article 670 Industrial Machinery, 670.6 Surge Protection
2NFPA 70 edition 2014, “Data Assessment for Electrical Surge Protective Devices”
3NFPA 79 edition 2018
4NFPA 79 edition 2018, Annex C, Examples of Industrial Machines Covered by NFPA 79
5ANSI C62.41, Low-Voltage AC Power Circuits
6ANSI C136.2, Roadway and Area Lighting Equipment - Dielectric Withstand and Electrical Transient
7UL8801, Outline of Investigation for Photovoltaic (PV) Luminaire Systems
8UL1598, Luminaires
9UL924, Emergency Lighting and Power Equipment
10UL1449 5th Edition, Surge Protective Devices
11UL497B, Surge Protectors for Data Lines and Fire-Alarm Circuits
12UL497E, Antenna Lead-in Conductors
13UL508, Industrial Control Equipment
14IEC 61643-11, Low-Voltage Surge Protective Devices - Part 11: Surge Protective Devices Connected To Low-Voltage Power Systems - Requirements And Test Methods
15IEC 61643-21, Low Voltage Surge Protective Devices - Part 21: Surge Protective Devices Connected To Telecommunications And Signalling Networks - Performance Requirements And Testing Methods
16IEC 61000-45, Electromagnetic Compatibility (EMC) - Part 4-5: Testing And Measurement Techniques - Surge Immunity Test
17CSA 107.1, General Use Power Supplies
18CSA 141, Emergency Lighting Equipment
19CSA 250, Luminaires
20NOM-001-SCFI, Standard for Electronic Equipment
21NOM-003-SCFI, Electrical Products - Safety Requirements
22UL 121201, UL Standard for Safety Nonincendive Electrical Equipment for Use in Class I and II, Division 2 and Class III, Divisions 1 and 2 Hazardous (Classified) Locations

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Where to purchase Citel SPD's