Why Test with Digital Instrumentation

Why test?

Making and interpreting measurements is a crucial part of any job involving service, installation, design verification, engineering, or factory support of HVAC/R equipment.  When it comes to verifying proper operation of the installed equipment it is critical that measurements made in the field are just as accurate as those made the laboratory. At Trutech we believe that we all have an obligation to assure that the equipment is operating at peak performance levels for the benefit of consumers and end users of HVAC/R equipment, equipment manufacturers, utilities, the nation’s energy future and the environment. Today, most AC & refrigeration equipment is still being serviced and adjusted with traditional mechanical manometers and manifold gauge sets using limited resolution temperature pressure charts or hard-to-read refrigerant gauge scales to determine evaporation and condensation temperatures.  Measurement errors can be the result of interpolation errors, calibration errors, poor repeatability of the measurement, and most importantly not having a procedure in place to consistently repeat the measurement process.  Before one can rely on these measurements, it is imperative that the same results can be obtained by anyone using similar instrumentation.  


Theories vs. facts

Air conditioning is not theory; it is a collection of scientific facts.  It combines physics, chemistry, and earth science.  We are concerned with the science of HVACR.  Science involves proven scientific facts that are repeatable anywhere in the world. For example, “pure” water will boil at 212° F (or 100° C) anywhere in the world at sea level.  Air conditioning is a well-proven science, and nothing more than that.  As with any science you must master the scientific principles, terminology, and mathematical relationships to fully understand what is happening. 

Start with the basics

As you approach the task at hand, it is important to master the basics or fundamentals first. It will always come back to that.  Many times a young mechanic finds the problem before a seasoned mechanic just because the young mechanic has recently mastered the basics and is looking for the simple problem that the seasoned technician has overlooked.  Additionally, a seasoned technician may see the problem, remark on it then completely pass it by because they think it can’t be that simple.  To be a good mechanic it is important to use your senses to troubleshoot the equipment; to look, listen, touch the lines (refrigerant lines not electrical lines!), make measurements and compare them to a known. Form a concept in your mind about what is happening, and then use the science you have learned, and the measurements you have made to either prove or disprove the concept.  

Measurement Technology: Why go digital? 

 Many service technicians are reluctant to use digital instruments; there is a certain comfort in using what we are used to.  The truth is digital instruments are faster, more accurate, more reliable, and have a higher repeatability than analog tools.  Digital instruments stay in calibration, allow trending, allow more complex functions and save time.  Digital instruments allow data to be recorded and reported with out human error, and provide reliable and accurate results for you and your customers.  Data can be recorded much faster than any technician could ever do the calculations and data can also be recorded whether or not the technician is there to see it.  In most cases, the data is an un-editable record, so what you see was what was measured at the jobsite. System trends and symptoms can be recorded with the function of time allowing the user to track cycles, and determine if other systems external to the refrigeration system like automation or shift changes are the cause of the problem. Permanent records allow the user to track system changes and determine if the system is operating within the design parameters or if changes have taken place. 

Charging by supheat and subcooling


Using the Testo 523/556/560 refrigeration analyzer is no different than using a conventional manifold gauge set, yet the system operation information available to the user is far superior. The high and low side connections are attached to their respective sides, and the readout of the refrigerant pressures and saturation temperatures are displayed.  The analyzer reads pressure and temperature only, so it is important that the refrigerant is known before verifying the saturation temperature as the 523/556/560 calculates the refrigeration saturation temperature.  The refrigerant selection can be changed any time during the analyzer use.  A temperature sensor (attached to the temperature probe port) will allow the 523/556/560 to calculate refrigerant superheat or subcooling and/or measure surface, fluid or air temperature with an auxiliary probe attached.   The Testo 523/556/560 is a laboratory-accurate instrument designed for use in the field by all refrigeration and air conditioning service technicians.  The 523/556/560 is designed to replace your existing manifold set, and should be the first tool of choice when working on refrigeration systems as additional information on system operation, and an operational performance curve can be obtained when desired.   Going digital may feel awkward at first.  From experience you know approximately where your gauge pressures should be.  Sometimes, unless the pressures are outside of the normal operating range, you may not even pay attention to the actual system pressures. A large part of the problem is that the user interprets analog gauges. Secondly, they are only an indicator of the approximate pressure.  If 10 users were to attach their gauges to an operating refrigeration system, even if all were calibrated, there would be a range of pressures and saturation temperatures interpreted by the users. (We know, we have tried this!)  Digital leaves no room for interpretation; it is what it is.  With digital, you will find yourself setting up the equipment exactly to the manufacturer’s specifications because you can. If the manufacturer calls for 8° of subcooling, you can charge the system to exactly 8°. There is no learning curve beyond learning to navigate the menus of the analyzer.     When using the software it is important to not let the amount of information obtained by the system analyzer overwhelm you. The Testo 556/560 can measure and store 1000’s snapshots of the system operation including the high and low side pressures, corresponding saturation temperatures, actual measured temperatures, and the calculated superheat or subcooling at any given instant during system operation.  All of the information can be displayed graphically on one page in the EasyKool PC software.  This allows the user to see the big picture, and notice things like TEV hunting, pressures rising or falling, cycling, and see when the system has reached steady state operating efficiency.  

All or part of the information can be displayed at once making it easy for the service technician, installer or lab technician to view the suspected problem in greater detail than ever before.  Using the refrigeration system analyzer will forever change to way you troubleshoot refrigeration/air-conditioning problems, as you will have a “digital window” into the refrigeration system. 

Portions excerpted from the Testo A/C Applications Guide 

Used with permission


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