Sealed System Repairs (part 2)

In the first part of this series (part 1), I talked about the basic equipment needed to perform sealed system repairs. Now that we have an idea on what we need, in terms of tools, let’s talk about the most important aspect of the work; safety.

If you’re not experienced using a torch or some other form of brazing or soldering equipment, it would be advisable to take a course at a local trade school and practice swagging and joining tubing before attempting to make repairs in a customer’s home. Skills have to be acquired through repetition. Applying just the right amount of heat from your torch to a joint will determine the flow of the solder and the integrity of the connection.  You should also make sure you are properly compliant with the EPA. Your local supplier can usually provide information on where to get certified and under no circumstances should you ever vent freon into the open air. It is illegal to do so. Aside from being destructive to the environment, there are heavy fines from the EPA if you’re caught. Penalties of up to $25,000 per day per violation can be levied and prison terms can be given to anyone who knowingly vents CFC-12 or HCFCs into the atmosphere. Regulations also require that these hydrocarbons be recycled. However, it is not illegal to use recycled, or remanufactured stocks of these chemicals.

Let’s get started. First and foremost, carry a small fire extinguisher in your tool box. The best way to prevent a catastrophe is to prepare for it.  I use a 16oz. Kidde bottle purchased from a home improvement center as it is small enough to fit in most tool bags or tool boxes. Remember, you’re working with fire, and refrigerant oil is flammable. In addition, be absolutely sure that any sealed-system you’re working on has been de-pressurized and evacuated of all traces of residual refrigerant. Just a warning, it’s better to be safe than sorry. Dichlorodifluoromethane decomposes into phosgene gas–a highly toxic and deadly nerve agent–at temperatures above 1000º F.

Let’s go through the process of replacing a compressor.

The first step in sealed-system repair would be to determine the correct diagnosis. Make no haste in this procedure; exhaust yourself in the diagnostic process. You don’t want to open a system if it’s not necessary; sealing everything back up is a tedious process. When you’re sure your diagnosis is correct proceed with the following:

  1. Shut the system off by removing the plug from the wall outlet or flipping the circuit breaker switch to off; check with a voltage meter if you’re not sure.
  2. If not equipped, install an access valve on the suction line, low pressure side of the system such as a bullet piercing valve.
  3. Connect your manifold, gauge and refrigerant hoses between the access port on the compressor and the inlet port on your recovery machine. Connect the discharge port from the recovery machine to a recovery tank or a charging column. You can re-use the recovered refrigerant as long as it is not contaminated. Charging columns allow you to visually see the condition of the refrigerant. If it’s discolored or if you’re replacing a compressor due to a burnout, you’ll need to filter the refrigerant by running it through a clean-up filter-drier before recharging the system to remove any acid or sediment.
  4. When the sealed-system is completely evacuated, close off the ports on your recovery machine and the recovery tank.
  5. Remove the filter-drier by cutting it out of the system. It is highly recommended that you replace the drier whenever replacing any component or opening up any sealed system.
  6. Disconnect all electrical wiring from the compressor and make a mental note of where everything goes, write it down if necessary or take a picture with your smartphone. Un-sweat all the connecting tubing or cut it with a tubing cutter. Remove the old compressor and seal all open lines by soldering them shut to prevent leakage.
  7. Remove the new compressor from the box and the protective plugs from the suction, process, and discharge ports and clean thoroughly with wire brushes and sand cloth. If the refrigerant lines on the compressor are not the same size as the existing tubing, you can use reducer couplings or swag out the line with a swag tool. Do not use a reducer if doing so would restrict the flow of refrigerant. When all the lines are fitted, coat them with the proper flux and solder the joints. Install a new drier equipped with an access port. I use Harris Safety-Silv 56, 1/16” diameter for all my soldering. It has a melting point of 1200ºF. CAUTION: Keep your eye on the torch at all times and be cognizant of how much heat it produces because it can burn and melt the majority of the plastics used on refrigerators today. When you’re finished soldering shut the torch off and place it down on a fireproof surface, not the customer’s floor. I carry a few pieces of 8”x8” aluminum plate in my tool box as a protective heat shield.
  8. Re-attach all the electrical wiring and compressor mounting bolts. Pressurize the system with an air compressor or nitrogen to at least 125psi, check for leaks. Use soap bubbles as a visual check. When you’re sure there are no leaks, open the access valve on the drier and allow all the air to escape. Reconnect the power, turn on the compressor and do a sweep-charge. A sweep-charge is a term coined by the Whirlpool Corporation and uses the compressor to evacuate all remaining air and moisture. Close the access port on the drier when the system is empty.
  9. While the compressor is running, weigh the proper amount of refrigerant into the charging column and charge the system through the low-side, suction side of the system with vapor. Do not charge the system with liquid or you will smash the reed valves and ruin the new compressor. If necessary, you can heat the charging column with a hair dryer to raise the pressure and facilitate the transfer of the freon. When the charging column is empty, close all the valves and allow the pressure to stabilize. If you weighed in the proper amount gas and have no leaks you should be okay. If your gauge is in a deep vacuum you probably have a restriction and you’ll need to check all you joints to make sure they’re not soldered shut.

That’s it in a nutshell. Each job will be different and you can use the same techniques to replace an evaporator and an heat exchanger, or if you find a leak in a sealed-system, such as a leaky evaporator or corroded tubing, you can usually repair it with solder.  Soldering aluminum is tricky but it can be done. I’ve repaired many punctured aluminum evaporators with a soldering technique I learned at a trade show from the Harris company using silver bearing solder and a special flux they manufacture. Check with your local supplier for special products manufactured by the Harris company for soldering aluminum. As mentioned above, be sure to practice until you acquire the skill.

There’s a lot more to sealed-system repairs than outlined here, but we’ve covered the basics. The secret to becoming a pro is to take your time and apply patience. Don’t rush through your jobs and be careful and aware of the customer’s property. Try to learn something new on each job and don’t throw down a challenge as these are the jobs you learn the most from. In time, you’ll become an expert, and experts demand higher salaries.

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