What if you are only given 3 measurements?
As HVACR technicians, you need some ideas in your back pocket for basic troubleshooting in a refrigeration system. How about a simple chart that helps you diagnose a system with 3 data points for starters?
Let’s take the following 3 data points as an example; compressor discharge pressure, suction gas pressure, and suction gas temperature with the latter 2 being taken at the evaporator outlet. Calculate superheat using the suction pressure and temperature. Using compressor discharge pressure, suction pressure and superheat we can compare to normal condition, lower than normal, or higher than normal.
To simplify this analysis, you will assume the system components, compressor, evaporator, condenser, and expansion device, are properly sized and the equipment is sized correctly for the original load.
For each of these combinations, you may assume the expansion device to be either a TEV or fixed restrictor, whichever you believe better explains the problem. See the chart below for basic troubleshooting.
Using this chart is simple and can greatly speed up the troubleshooting of a system. Other tools that can speed up your diagnosis is the SMART Service Tools that connect quickly and easily to allow you to get fast and accurate temperatures and pressures delivered directly to your smartphone or tablet. And, the ChillMaster P-T app readily converts all common and many uncommon refrigerant pressures or temperatures to the other for easy superheat or subcooling calculation.
Article contributed by Glen Steinkoenig, product manager, Thermostatic Expansion Valves, Sporlan Division of Parker Hannifin
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