Tag: infrared

infrared_yuck

There are three reasons why I don’t like infrared thermometers for many HVAC tasks.

#1 – The Laser is Misleading
The laser dot is just a point of reference, not an exact point where it is reading. Often the thermometer will read lower, higher or over a MUCH wider area. Unless you are right up on what you are measuring you can’t be sure the result you are getting is correct.

#2 – They Only Read Surfaces
An infrared reads surface temp only, not air temp. This is necessarily a problem, but “shooting a vent” is not the same as measuring the air temperature coming out of it.

#3 – They Can be VERY Inaccurate
Basic infrared thermometers are only accurate on a surface that has high “emissivity” of near 1.0. These are usually darker, less reflective, generally non-metallic surfaces. Metals have a low emissivity (much less than 1 generally) which means that if you are reading a pipe an infrared could read much lower than the correct temperature.

Infrared thermometers can be useful to do comparisons where reading the correct temperature is less important than comparing one spot to another, such as looking for hot spots in a panel, or checking a zone to see if a damper is open.

So long as you use the right tool for the job you should be fine, but in general….

I don’t like techs using infrared thermometers for most tasks.

— Bryan

P.S. – While I don’t generally like infrared, I REALLY like thermal imaging. Check out these nice products from Trutech tools 

Every HVAC/R tech needs an electronic leak detector nowadays and with HFC refrigerants getting more and more commonplace a VERY sensitive electronic leak detector. There are three types we often see but let’s toss out the corona discharge leak detector right off the top. It just picks up too many other types of chemicals to be useful and can easily result in false positives. This leaves the heated diode (or Pentode in the case of Tif) and the Infrared.

Heated Diode

The heated diode is the standard for sensitivity and the ability to pinpoint a leak. Some common heated diode leak detectors are the H10G, the Testo 316-3 shown above and the Tif ZX.

Advantages

  • You can move to the spot of the leak and hover over that point to detect very small leaks. This allows you pinpoint the leak.
  • Tremendous sensitivity on many models
  • Many techs feel they are more accurate because the motion is more intuitive. Place the probe over the leak and the detector goes off.

Disadvantages

  • Heated diode can give false positives from some other substances
  • The sensor is prone to fouling from moisture and oil
  • The sensors need to be replaced fairly often (usually at about 100 hours of operation)
  • The Sensor needs to be allowed to heat up before use

Infrared 

Infrared leak detectors are increasing in popularity over recent years. An infrared leak detector draws the sample across an optical sensor that analyses how much IR radiation the sample has absorbed. Some common types are the Fieldpiece SLR8 and the Bacharach TruPointe.

Advantages 

  • The sensors last longer than heated diode
  • They are less susceptible to false positives from other gasses and maintain full accuracy for a greater range of refrigerants
  • Very good sensitivity, though not generally as sensitive as the most sensitive heated diode models

Disadvantages

  • Infrared detectors compare samples to one another for detection. This means that the probe generally must be moved continuously to work properly. This can make pinpointing the leak more tricky.
  • It can be more difficult to get a sense of the size of the leak because they are constantly recalibrating (in my experience).

As is true in many things, you get what you pay for, so you should expect to pay $250- $550 for a good quality leak detector. If you stick with a quality brand and read up on the technology and sensitivity specs beforehand you will generally be in good shape with either a heated diode or a infrared leak detector.

— Bryan

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