Surge Protection for PLC Cabinet


Modular PLC

OVERVIEW

Today's increased reliance on very sensitive electronics makes surge protection an important topic for PLC Cabinets Listed to the UL508A Industrial Control Panels Standard. 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©.


PLC Cabinet

Selecting SPD for PLC Cabinets

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.

Main Service Panel | PLC Cabinet | Motor Controller Center | Motor

Recommended SPD for Main Service Panel

Location	Equipment	System	Surge Protector Model#	Link
	Main Panelboard	480Vac	MDS750E-480D

Recommended SPD for PLC Cabinet

Equipment	System	Surge Protector Model#
PLC Cabinet	120-240Vac Power Input	DS72US-240T/NN
P/S	24Vdc Power Output	DS220S-24DC
Analog Sensors	4-20mA	DLA-24D3
Discrete I/O	RS-485	DLA-12D3
Network Switch	Ethernet Cat 6A	MJ8-C6A
Radio Transmitter	SCADA Wireless	P8AX09-6G-N/FF

Recommended SPD for Motor Control Center (MCC)

Equipment	System	Surge Protector Model#
Motor Control Center	480Vac Power Input	DS74US-480D
Power Supply	120-240Vac Power Input	DS72US-240T/NN
P/S	24Vdc Power Output	DS220S-24DC
Analog Sensors	4-20mA	DLA-24D3
Discrete I/O	RS-485	DLA-12D3
Network Switch	Ethernet Cat 6A	MJ8-C6A

Recommended SPD for Motors

Location	Equipment	System	Surge Protector Model#	Link
	Motor	480Vac Power Input	M50-480D-A
		0-240Vac Relay Input	DS71US-275

Determining the acceptability of an SPD for your UL equipment

(for UL 508A 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

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.