Acid and Contaminants Testing w/ John Pastorello

John Pastorello from Refrigeration Technologies joins us to talk about testing oil and refrigerant for contamination. He also explains what each test is good for. John developed the Checkmate testing kit when he recognized a need to test reclaimed and recycled R-12 for acid and moisture.

The Checkmate method removed a small amount of refrigerant from the system for testing. The Checkmate apparatus hooks up to a refrigeration system to test the oil. You insert a tube with a rubber stopper, and you can draw refrigerant from the system when the tool pierces the rubber stopper; the method is similar to drawing blood. The kit then assesses the acid content in the refrigerant and creates a colored stain that indicates the acid content. You can use an included color chart to interpret the stain color.

Checkmate also assesses oil based on its dielectric strength; contaminants can give oil conductive properties, which the test picks up on. Unfortunately, oil breakdown can happen even when technicians use best practices, and it's commonplace on aging systems. Some tests only pick up on acid, not moisture. However, Checkmate picks up on the moisture content as well, which can be an indicator of future acid problems.

Many technicians don't perform oil testing frequently enough; if they test the refrigerant or oil at all, it's only infrequently, such as during PMs. More frequent testing could occur with easier testing methods, such as by using the Checkmate kit, and it could save HVAC system owners lots of money in the long run.

John and Bryan also discuss:

Diagnosing compressor burnout
Conductive oil
Gradual oil breakdown
Schrader core testing devices
PVE oil
Air and moisture skewing other test methods
Vapor testing
Venting exemptions for acid/moisture testing (de minimis)
Checkmate tube shelf life
Suction driers

Learn more about Refrigeration Technologies HERE.

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Author:

Bryan Orr

Company: HVAC School

Position: Founder

John Pastorello

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In this short Q&A podcast episode, Bryan answers a listener-submitted question about superheat, including what it is and how we measure it.

Superheat is the number of degrees a refrigerant is above its saturation point. The saturation point is where you will have a liquid-vapor mix, so superheat only exists when a substance is a vapor. Saturated refrigerant should only exist in the evaporator and condenser, during which it is being boiled or condensed.

We usually measure superheat at the evaporator coil outlet and compressor inlet. The superheat at the evaporator outlet is usually around 5-14 degrees Fahrenheit, and it’s often between 10 and 20 degrees at the compressor inlet (compressor superheat). However, many systems try to get lower superheat values, and some manufacturers may require higher superheat values at the compressor inlet to prevent liquid refrigerant from getting into the compressor. Accumulators can help keep liquid refrigerant out of the system as well. We may also measure superheat coming out of the compressor on the discharge line (discharge superheat); this superheat may exceed 100 degrees Fahrenheit. Discharge superheat can let you know if the compressor is overheating the oil and causing breakdown or carbonization.

We use superheat to set the charge for fixed-orifice metering devices (as opposed to subcooling for TXVs), as superheat is a measure of how well we’re feeding our evaporator coil. When the system is off, the superheat will be 0. A system will equalize, and the refrigerant will be at saturation when that happens.

Have a question that you want us to answer on the podcast? Submit your questions at https://www.speakpipe.com/hvacschool.

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