Using Data Loggers For Service

Occasionally, a service technician will encounter a problem that may not be evident while he is at the jobsite. The problem may be intermittent, and it may not occur while he is on the job.

This can be quite frustrating for any technician. He shows up to solve a problem for a customer, only to find the system running normally with no signs of a problem. Then, several hours or maybe days later, the customer calls again complaining that the system still is not working.

Hopefully, after the technician arrives at the jobsite for a second visit, he will be able to see the real problem and resolve it. Other times, however, the technician arrives on the job only to find the system running normally again. This can be uncomfortable for a technician. The customer is complaining about a problem and the tech has no answer.

Sometimes a technician may elect to guess at the problem and start changing out components, hoping to get lucky and change out the one that may be the cause. This could lead to more problems. If he did not guess correctly, not only will the customer be complaining about the problem still existing, but now he has also changed out a component that didn't need replacing. This can be a real uncomfortable scenario, and certainly not one a technician wants to face.

Practical Answers

There may be a practical solution. A service technician can use various types of data loggers to record system conditions and determine the true cause(s) of a problem. Data loggers are available that can record just about any system condition, including pressure, temperature, humidity, voltage, amperage, and even closure of a door or a switch. A technician can log one or several of these conditions and then later scroll through the recorded data to determine when a problem occurred and what the system conditions were leading up to the failure.

This can be a powerful tool to resolve odd problems. Instead of guessing at the possible cause, a technician can install one or more data loggers, record relevant system conditions, then troubleshoot the system properly.

An Example

Say a technician is called out to service a large walk-in freezer. The system keeps tripping on the oil pressure control.

Each time the technician arrives on the job, he resets the oil pressure control and then measures the net oil pressure of the system to be within the range stated by the compressor manufacturer. The technician tests the oil pressure control and it tests OK.

Unsure if there is a system problem causing the oil pressure to trip, or an intermittent problem with the oil pressure control, the technician installs a data logger to record the system's oil throughout the night.

The next day the oil pressure trips again, but this time the technician is able to view the data logs and see when it tripped and what the oil pressure was before it tripped. With this vital information, he now can accurately troubleshoot the true cause of the problem and repair it.

Joe Marchese is owner of Coldtronics, Pittsburgh. He can be reached at 412-734-4433,, or

Publication date: 09/05/2005

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