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How To Troubleshoot A Chiller?

Oct. 17, 2022

You've just received a call from a new customer with a problem with his production chiller. The best way to help begins before you get to the job site.


1. The first step is to call the customer and ask for details of what is happening and the indicators or codes that appear on the diagnostic readings (if the chiller has them). If the customer does not know any details, ask him or her to check the following.


Is the water pump circulating water? What is the water temperature?

When did the chiller come off line and has this happened before? If so, when (can it be the same time every day or the same time every week)?


Is the chiller running rather than cooling, or not running at all?

These are key items that you can use as a troubleshooting starting point before arriving at the job site. Upon arrival at the site, follow the following outline of procedures.


2. Check that the information you received over the phone is correct.

Air Cooled Scroll Chiller

 Air Cooled Scroll Chiller


3. Once you have determined the accuracy of this information, check the obvious. Is the chiller running? If it is running, then perform step 8. If not, look for the diagnostic display panel that tells you where to start checking. Does the chiller have main power and control power from the transformer? Check all fuses. 


4. Write down any codes listed on the chiller (most newer chillers have diagnostic codes or alarm codes available for viewing). Look for the cause in the unit's troubleshooting manual. Make sure the company can get it for you, even if you know the chiller.


4a. If the chiller is not running, find the electrical diagrams for its control and high voltage circuits. This will be necessary for older chillers that are not equipped with built-in diagnostics. The reason the compressor is not working is usually due to an "open" condition somewhere in the control circuit. You need to find where the open condition is located. Use the electrical diagram to find it.


4b. Starting with the power side of the transformer, check it wire by wire. For those jobs where you do not have access to the electrical diagram, or when the chiller is located in a place where you cannot read the model number or see any diagnostic lights or codes, always start with the control transformer and follow the control power line path. Locate the power side and use a good voltmeter to trace the power line from safety to safety. Eventually the control power will reach the compressor or pump contactor coil.


Another way is to work backwards from the compressor contactor control coil to the control transformer. Along these paths you will find open circuits, if any. 

Box Type Water Cooled Scroll Chiller

Box Type Water Cooled Scroll Chiller


5. If you find an open condition, then you must determine the cause. It could be anything from low pressure to a damaged compressor control module.


Chillers usually have two unique safety features: one is the water flow switch, which can be hidden in the plumbing and is not visible, especially if you have a remote pump tank system. The second security is the freezestat control. freezestat is basically a backup thermostat that ensures that the water supply temperature is not too cold. Typically freezestats are set to 10F below the temperature of the water supply that the customer wants to run. 


6. Visually inspect the chiller electrical panel, plumbing and pump tank system (if any). You may see obvious problems such as burned or disconnected wires, pumps not running, water valves closed, and improper system water temperature. 


7. At this point, you should have found which safety device has tripped. Do not reset the compressor and oil pump (if applicable) until you have gauges on it. Install temperature probes on the suction, discharge and fluid lines. Place an amperage meter on the high pressure branch of the compressor prior to starting the system. Reset it safely. Then watch all pressures, temperatures and currents at the same time. This is not an easy task, but necessary, especially within the first five minutes.


8. Measure the antifreeze concentration in the system. If the system has no antifreeze, check the water quality. The best way to measure antifreeze is with a refractometer. Remember, if the system uses ethylene glycol or propylene glycol, the freezing point will be different for the same percentage.


For more information about the troubleshooting common chiller problems, welcome to contact us at +86 15262310939 or write to us at j.li@szhuateng.com. We will be happy to help you out!

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