Micron Gauges Gone Wild

We've been getting many questions on micron gauges that are ”going haywire” or reading in the micron range, even at atmospheric pressure.

First, micron gauges measure absolute pressure, so you can’t ”zero” them out.

They use tiny, very sensitive sensors that are calibrated to air, not refrigerant, so anytime refrigerant gets into the gauge, it's going to read a little wacky.

This often happens when pulling a vacuum on systems that previously had refrigerant in them, especially when pulling on the compressor because refrigerant pulls out of the oil as the pressure drops.

The best way to counteract these readings is to flow/purge with nitrogen prior to the vacuum, and just keep in mind that as refrigerant passes by the sensor, it may act a little erratic for a while. This will stop occurring as the refrigerant is removed.

If the gauge is reading incorrectly when open to atmosphere, you can just blow a bit of air or nitrogen into it to get it back to normal.

These erratic readings are not a problem with the gauge; they are an expected behavior when refrigerant hits the sensor.

—Bryan

P.S. – If you're interested in learning more about microns and micron gauges, please read this article.

Comments

Related Tech Tips

You're Grounded
One of the most common questions we get from techs is about using a voltmeter to diagnose a high voltage circuit. It's especially tricky when a tech is used to working on a low-voltage or 120V circuit, where there is a clear “hot” side of the circuit and a clear “grounded” side of the circuit. […]
Read more
Does An Oversized Furnace Consume More Fuel?
This article was written by Michael Housh and was inspired by a discussion that took place on the HVAC School Facebook group. If you are already a member of the group, you can look at the oversized furnace discussion yourself HERE. I'd like to give a special thanks to Michael and everyone who contributed to the conversation. […]
Read more
What is a GFI?
First off, the correct acronym for a GFI (ground fault interrupter) is “GFCI” (ground fault circuit interrupter). The purpose is to act as a safety device to protect from electrical shock. GFCIs are important components of electrical safety. GFCIs can be built into outlets, circuit breakers, and even extension cords. We generally use them for […]
Read more
loading

To continue you need to agree to our terms.

The HVAC School site, podcast and daily tech tips
Made possible by Generous support from