Retrofitting a 1980s Coin Op 7-UP vending machine in Austin, Texas
The 80s were a long time ago. Some people born in the 80s are now over 40 and that is kind of hard to believe. More shocking than that are the machines that have survived from the 80s. We recently were called out to fix a 7-UP vending machine in Round Rock, TX made sometime in the mid 80s and found it had a leaking cap tube. The company who made the machine was long gone and this machine used an obsolete refrigerant called R12. R12 was a fantastic refrigerant that was invented in 1931 but was not very environmentally friendly due to Chlorine in the formula. It had a good ride and was phased out in 1992. It was used in a variety of capacities from refrigeration to automobile air-conditioning.
The repair for a leaking cap tube requires the system to be opened. The process involves removing the refrigerant if there is any that has not leaked out, replacing the cape tube, replacing the filter drier, pulling a vacuum and recharging the system with new refrigerant. But, wait! What if that refrigerant doesn’t exist anymore? There is not a modern refrigerant that can be used in the same exact capacity as R-12. There are some that are similar but nothing exactly the same. The properties of refrigerants are not all exactly the same and they all have slightly different boiling and condensing points which makes them all rather unique. There are some that are close to the same specs which enthusiasts will recharge their systems with but those are not tried and true methods that will continue to function for another 35 years.
For this situation we opted to replace the compressor and cap tube with a compressor rated for a modern refrigerant. We chose R134A, the refrigerant that was used in household refrigerators and automobiles after the phase out of R12. You more than likely have a car and fridge today with R134a. We sized a new compressor and cap tube to contain the same BTUs as the old system but we opted to keep the original condenser and evaporator coils.
What steps does this involve? A lot. Firstly the old compressor will be cut out and unbolted. It will be sealed by brazing the copper pipes closed so it will not leak oil on the way to the recycler. We will then cut out the cap tube and filter drier and recycle them as well. It is good to mention right now that there is a shortage of copper in the world at the writing of this blog and it benefits everyone to recycle as much metal as possible to help keep up the supply. When possible, we recycle all metals and refrigerants. Wasting resources is well…..wasteful.
Once the old parts have been cut out we will bolt in the new compressor and repipe the copper lines to fit the new configuration of the compressor. There is about a 99% chance that nothing will line up to where the old compressor’s copper lines were situated so some adjustments will need to be made to make the new compressor work. We will install a new filter drier and cap tube and braze everything together.
This system is called a sealed system. This means there are not ports to access the refrigerant. Imagine the refrigerant system is like a bike tube. How do you get air in the tube? You use the Schrader valve which you connect your bike pump to. For some refrigeration equipment the manufacturers do not want people to access the refrigerant in the system so they do not provide a Schrader valve. (Schrader valves are used in refrigeration too, but they are a different size) It’s like having a bike tube without a way to add air. Well that won’t work for a technician trying to work inside the system so the technician also adds Schrader valves to the system to give access. This is how to pressure test the system with nitrogen, pull a vacuum and charge the system with new refrigerant which is what we do after replacing all of the parts.
Something to mention with small refrigeration systems like your home fridge, chest freezer or your car is that they require a critical charge. What the heck does that mean? It means that it will only work properly if charged with exactly the amount of and type of refrigerant that the manufacturer specs out. Where do you find that information? You will find that on the data plate where the model number is. If it is a refrigerated appliance of just about any type you will find this useful information on that data plate. (Just for fun the next time you are at a Redbox getting a movie, look on the side, find the data plate and marvel at what refrigerant it uses and how much it needs.)
Once you know the type and how much refrigerant it requires it’s easy to charge a system but what happens if you have changed the system to operate using a new refrigerant? It will certainly not use the same amount of refrigerant since the type of refrigerant is different. So how do you charge it? Superheat! Superheat is how you measure heat beyond the boiling point of a substance. You charge the system and base the amount you charge it on the superheat calculation while the unit is running.
The best way to explain superheat is to think of boiling water. Water boils and turns to steam that floats away. As the steam cools it turns back into water. But what if you didn’t let the steam escape and instead kept boiling the water into steam in an enclosed space? The temperature of the steam would go above the boiling point ‘superheating’ the steam. That’s what superheat is. Similarly the refrigerant coming out of the evaporator of a refrigeration system is superheated. THAT is what we measure.
At this point you will have a machine that makes things cold again. Go ahead. Put $.15 in the machine and enjoy a 35 year old 7-UP. It’s the ‘uncola’ or so they said way back then.
Or check out our website at www.tripointrefrigeration.com
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