CHART RECORDER - Defined

So what is a chart recorder?

A chart recorder is an interesting and valuable tool that can provide a ton of information regarding the operation of a piece of equipment. A Chart Recorder has a temperature probe and a digital display readout indicating current temperature as measured at the probes location. The unit pictured above works on a dial or "clock like" rotation with a graphing chart and can record temperatures on the chart in a 6-hour increment, 24-hour increment, 7-day increment, or a 31-day increment.

The versatility of this tool can eliminate costly man hours (service hours) and frees up the tech to work on other things while keeping an eagle eye on a piece of equipment at the same time.

In my business, this is one of the most valued tools I own. Each piece of equipment I sell will have a chart fastened to it as a "peace of mind" for my customer.

You see, this unit will record EXACT temperatures of the unit including cycle times of the compressor (on/off) as the temperature fluctuates inside the unit. This is critical to determine:
(1) if the Troubleshooting Temp control (thermostat) is working properly
(2) if the compressor is shutting off as design
(3) if the range on the temp control is good
(4) adjusting the temperature or "dialing" in a temperature
(5) if the unit is going into defrost, and
(6) how many times in a 24-hour period it defrosts

I have seen countless units that "worked" or "got cold" so ordinary, non-informed consumers think - wonderful; "I will take it" only to find out later the unit is icing the coil or not running right. And, for these and many other reasons I am convinced this is a must have when servicing or selling refrigeration equipment.

FUNNY STORY: I went to look at a used cooler someone had for sale advertised locally on Craigslist: when I arrived the cooler was in the mans garage and plugged in. I could hear the evaporator fan running but could not hear the compressor. Of course I did bring along my digital thermometer which records similar to the recording thermometer pictured above only my digital also records in tenths of a degree. The owner was a bit surprised when I pulled out the digital and put the probe in the unit to check the temperature accurately. You see, he was trying to tell me the unit worked great as the thermometer he stuck on the shelf indicated 32*. The problem? Well, it was the dead of winter in Michigan and the "cold" temperature inside the box indicated by his thermometer was actually the "air" temperature....the unit was not cooling at all and in fact the compressor was not even running. You see I adjusted the temperature control all of the way up and all of the way down and watched my digital to see if there was any temperature change - when there was none, I knew it wasn't working.

I tell this funny story only to convey a real life scenario where a non-informed shopper could easily be taken advantage of. Unfortunately the every day shopper doesn't have a digital thermometer but the point is - BEWARE of a man selling a cooler out of his garage that is full of odds and ends that looks like Sanford and Sons. A true professional will be happy to show you how the unit works and exactly that it is working according to the manufacturers specs and do so in a typical "heated" working environment.

Just recently I picked up a 2-door, glass door freezer from a nation wide pharmaceutical chain. Once I got the unit to my shop I plugged it in and noticed immediately the unit got cold. I immediately utilized my graphing thermometer to check the unit out. When I returned the next day I noticed the unit showed a "flat line" of -24* with 4 spikes. The spikes indicated the unit went into defrost every 6 hours. The flat line indicates the compressor never shut off and continually ran. The unit was on full time at -24* but trying to get colder. Obviously, this creates unnecessary and damaging run time on the compressor thus reducing the life of the unit. A simple Diagnosing Temp Control revealed the thermostat was indeed bad. I simply replaced the temp control and re-graphed the unit. The problem was solved - and simply too as I didn't need to diagnose any further or waste time baby sitting the unit to see if it cycled correctly. Or worse yet, sell the unit to someone without knowing the problem and having an angry customer once the unit iced the coil or trashed the compressor.

Not having the recording thermometer, typical Mr. Customer would see the unit was cold and may even get excited the unit was at -24* possibly thinking colder is better. Unfortunately, he may not be aware that the temperature control is bad thus reducing the life and longevity of the unit. BE INFORMED - BE AWARE!


As you can see with the chart example above. The unit that was charted on the graph is operating perfectly. The short spikes indicate the temperature cycles - compressor on and off once satisfied. This too proves the thermostat is functioning as designed.

The larger spikes indicate the times the unit went into defrost. Here the unit is programmed to defrost once every 6 hours. The neat thing with the graphing thermometer is it is easy to tell how long the unit was in defrost and the exact time of a day the unit defrosts. This is important for high volume customers who would rather see the unit defrost "after hours".

After hours defrosts can eliminate or reduce "melted" product, false alarm scenarios (where an employee notices the unit is warm and not running and then calls the repair man), and allows the owner to be certain when the unit defrosts by knowing the exact time it is scheduled to defrost.

As you can see, there are many benefits to having and utilizing a chart, graphing, recording, thermometer.