On Monday November 19th 2018, I started rebuilding a walk in cooler for one of my customers. After a thorough inspection of the system, I found that the low side head pressure control, the liquid receiver, the condenser coil & condenser coil fan, and the compressor were in good operating condition – every other component of the machine was in poor condition.
The existing evaporator coil was leaking refrigerant from the center of the coil and was an obvious candidate for replacement. The TX Valve, solenoid valve & coil, and thermostat, while functioning, appeared to be in very poor condition.
Further inspection revealed that the evaporator coil and its related components were original to the system, whilst the compressor, condenser coil, etc. (i.e. the compressor package) was replaced about 8 years ago. The evaporator coil, TXV, solenoid coil, and thermostat were 21 years old. Also, it’s worth noting that the low side pressure control that was installed on the compressor package saved the compressor because it shut it down when the evaporator coil leaked out all of the refrigerant.
Because the system was out of refrigerant gas, I was unable to test the TX Valve. I was, however, able to test both the thermostat and the solenoid valve and coil, both of which tested ok despite their age and appearance.
When I changed the evaporator coil, I chose to change the copper linesets, the solenoid valve and coil, the Thermostatic Expansion Valve, and the thermostat as well. This decision added about $500 extra to the final bill for the customer.
So, the question is then, did I make the right judgement call by replacing parts that otherwise appeared to be functioning properly? If I base my judgement simply on the appearance of the parts it would seem like a good decision. But regardless of the appearance of the parts they tested out well and were functioning properly.
Why, despite the fact that the parts tested good and were functioning properly, did I chose to replace them?
Although the parts functioned well, they were original to the system and to the evaporator coil. Given the age of the coil and the parts, it’s reasonable to assume that these parts have literally cycled on and off hundreds of thousands of times. For example, if the machine ran an average of 16 hours per day, and cycled on and off 4 times per hour (both assumptions are conservative), in a 21 year time span the machine will have cycled on and off 490,560 times. That is both a testament to how well made commercial refrigeration equipment is, but also highlights how hard a commercial refrigeration system works to maintain a set temperature within a refrigerated space.
The machinery works quietly in the back round doing its job unnoticed hour after hour, day after day, and year after year, often with little or no maintenance being performed on the machine.
In this situation, I chose to replace the parts even though they were still functioning because I am aware that the parts have very high cycle times already. If a piece of equipment has moving parts, eventually those moving parts will fail.
In the case of this machine in particular, it is probable that the contacts on the thermostat, and the solenoid valve have opened and closed close to half a million times. The solenoid coil also has energized through a half million cycles. The TX Valve has likely modulated open and closed ten million times.
When I get called in to replace parts on a refrigeration system, I have to use my best judgement to determine what is the best course of action for my customer. I could have re-used all the parts discussed in this example (not including the evaporator coil, of course) but given their age and their cycle count, would I really be doing a service to my customer if I chose that route? I guess that it isn’t impossible that those parts could have lasted a few more years, but my customer would be gambling that their refrigeration system would not break down again in the near term future. That scenario could entail loss of product, loss of business, and more repairs bills.
I chose to scrap as much of the system as was practical so that my customer would have the best chance at having a reliable problem free refrigeration system.