Page 38 - Climate Control News May 2021
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                  Troubleshooting Tips
  20 degrees in mid-seasons the building could be cold inside although the outside tempera- ture is rising. Despite this some systems will not ramp up. This is normal. You will be able to see the operation limit in the Engineering Manual and save yourself time. Since the sys- tem's behaviour today is based on software, many algorithms and procedures run in the background. The algorithms that the unit follows are described in the manuals. It is easier to tell if the unit works properly if you understand what it should do in the first place. The manuals will also provide you with the best practice for diagnosing a spe- cific unit, and how to make a proper error re- claim from the unit.
4THE SYSTEM DOESN’T SEE TEMPERATURE AND PRESSURE ONLY RESISTANCE AND VOLTAGE. Sounds simple but it might be very challenging. The thermistors are alternat- ing the temperature to resistance, the pressure transducers transform pressure to voltage. Based on that information the HVAC system makes decisions. And here is where it becomes tricky. If the component is 100 per cent faulty the unit will give you an error code, however, if it is misreading the temperature by just a cou- ple of degrees (Ohms) or the pressure by a few Pascals (Volts) the unit will work but not as ex- pected, and an error code will not appear. And
“INVERTER SYSTEMS TAKE UP TO 30 MINUTES TO STABILISE, SOMETIMES EVEN MORE.”
here it becomes even more complicated. In some cases bench tests can give you the right value (the value you should see according to the service manual), but if the component is faulty it might be falling under certain condi- tions. For example, you have a hairline crack on a thermistor shell, but issues will only arise when moisture gets inside. To be able to prop- erly diagnose this you need to have access to a monitoring tool. All HVAC companies offer a diagnostic device that connects to the system on one side and your PC / Cell phone app on the other side enabling you to see what the unit can see and compare it to your actual measurements on-site (your pressure gauges and temp readings). In many cases, just by connecting the device, you will be able to iden- tify a faulty component.
5
difference between the return air thermistor to
LEFT: Be patient and allow the unit to stabilise.
RIGHT: Get
a monitoring tool and learn how to use it.
the setpoint (different systems have other fac- tors as well, but this is the basic one that I will use for this example). If you want to diagnose the system on a mild day, it might be idle in low frequency and will not increase the compressor speed. To force the unit to ramp we need to use the test run/trial operation. The unit will force itself to increase the compressor speed, and if it won’t, the unit is diagnosing itself by doing it. You have to allow the unit to ramp properly (de- pending on the system it might take a while). Finish the procedure to get a full picture of the unit operation. If you have a monitor tool con- nected it will provide you with valuable data about the system’s behaviour/protection. Every manufacturer and every model has a different procedure so please refer to the specific system manual for instructions.
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Let’s say you suspect a refrigerant shortage and decide to add refrigerant. The system will need time to digest the refrigerant and show some kind of change on your gauges. If you don’t see the change, wait. The same goes to testing operations. It takes time. Don’t rush. On a side note, many times I am asked to ana- lyse a system’s behaviour, and there isn’t enough data to get any conclusion.
      CLIMATECONTROLNEWS.COM.AU
GET USED TO TESTING RUN/TRIAL OPERA- TION. The basic reason for the system to increase the compressor frequency is the
ALLOW THE UNIT TO STABILISE. INVERTERS SYSTEMS TAKE BETWEEN 15 TO 30 MINUTES
(AND SOMETIMES EVEN MORE) TO STABILISE.
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