Heated Diode Detectors

With a heated diode detector, sampled air is heated to a high temperature, ionizing halogenated refrigerant gases. The resulting charged chlorine and fluorine ions, even in trace amounts, generate current through the diode which then triggers an alarm. Heated diodes detect leaks of HFC, CFC, HCFC, HFO, H2N2 (Tracer Gas), and other refrigerant blends. The Fieldpiece DR58 Heated Diode Leak Detector performs particularly well with R410A and sniffs refrigerant leaks as small as 0.03 oz/yr – that’s 20 times more sensitive than soap bubbles.

Heated diode detectors are not prone to false alarms, but their sensor life may be affected by excessive refrigerant exposure and contaminants like oil. The sensor should be checked regularly with a calibrated reference leak. It is recommended to replace the Fieldpiece DR58 sensor after approximately 300 hours of use.

Corona Discharge Detectors

In a process similar to heated diode detectors, corona discharge detectors also react to a change in current flow from ionized gases. However, they pull sample air through an electrical field around an electrode. Gases are broken down by the electric arc (corona discharge), causing a change in electrode current which then signals a leak.

False alarms can occur with corona discharge detectors because they do not trigger on specific refrigerant compounds. Response times are slightly slower than heated diodes and corona sensor life can be as short as 24 hours of use.

Infrared Leak Detectors

Infrared detectors shine a beam of infrared (IR) waves through potentially contaminated air to detect and analyze trace amounts of refrigerant and signal a leak. Because light absorption in the IR spectrum is gas-specific, they are the least susceptible to false-positive alarms and are considered highly accurate across all refrigerant types. Infrared detectors also have the edge with newer refrigerants that contain less chlorine and fluorine, the trigger for heated-diode sensors.

When considering the cost of ownership of a leak detector, the long life of the infrared sensor will factor into the equation. For example, the sensor life is approximately 10 years for the Fieldpiece DR82 Infrared Leak Detector.

Ultrasonic Leak Detectors

An ultrasonic leak detector is also known as a “listening detector.” When refrigerant escapes from a pressurized system, it creates tiny sound fluctuations in the form of high-frequency sound waves that the sensor picks up.

These detectors can hear very small leaks on high-pressure systems and their sensors last for a long time. However, when a system has low pressure, these detectors are not as accurate or effective. Ultrasonic leak detectors can also be affected by job site noise.

Techs have multiple options when looking for electronic leak detection tools, including heated diode, corona discharge, infrared, and ultrasonic. While each has its merits, the tool that’s right for you will depend on the refrigerants you work with now and expect to work with in the future, the accuracy desired, and your sensitivity to the overall cost of ownership. An electronic leak detector is an investment that makes your job easier, so it’s worth the homework to figure out which one needs a spot in your tool bag.

This guest column is courtesy of Fieldpiece Instruments.