Surge Protection for Dual Resistance Temperature Detectors (RTDs)

OVERVIEW

Today’s increased reliance on very sensitive electronics makes surge protection an important topic for most industries. 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©.

A Resistance Temperature Detector (RTD) is a key component of any UL 508A control panel (also known as an Industrial Control Panel or ICP). However, they are usually overlooked due to their limited cost in the overall system yet are integral parts that can lead to costly and disruptive downtime. The Resistance Temperature Detector or RTD is used to measure temperature in applications found in food processing, refineries, chemical plants, power plants as well as commercial, industrial, residential and manufacturing process applications. They are the critical components in the process loop and are sensitive to transient over voltages.

This section will identify the UL 497B Surge Protective Device (SPD) to efficiently protection your RTD and increase its reliability.

Protection Point for
Dual Resistance Temperature Sensors

Based on the built-in withstand of the equipment, most of the temperature probes can be protected using the SPD shown below :

Location	Equipment	System	Surge Protector Model #	Link
	Dual RTD Input	4-20mA (2-pair wire)	DL2A-24D3
	Transmitter Analog Input	4-20mA Current Loop 3 or 4-wire	DLA2-24D3
	Transmitter Analog Output	4-20mA Current Loop 3 or 4-wire	DLA2-24D3
	Transmitter DC Power Input	24V DC	DS220S-24DC
	PLC Analog Input Card	4-20mA Current Loop 3 or 4-wire	DLA2-24D3