Ok, I recently made a repair on a broken refrigent line as detailed here:
It was my very first attempt and I surprised myself in that it worked perfectly good and I learned so much in that exercise. I greatly prefer low temperature soldering over high temperature brazing. I'm a hobbyist and not a professional HVAC installer. I don't want to spend additional money on brazing equipment plus I have so much fun with my propane torch.
The repaired line developed a tiny leak on one side of the joint. This was due to me twisting the line a bit to fit it into a cooler. The leak appeared five days after testing of my chilled water project. Now I need to repair this leak!
Step 1: The Repair Materials.
The refrigerant I removed by opening the service valve I previously added and now the system was ready for me to apply heat! The reason the original repair failed is because I relied only on the mechanical strength of electronics grade solder (which is surprisingly strong once properly applied).
I needed a filler material to fill the gap and to increase the strength of the soldered junction. This is very similar to steel bars for reinforced concrete. I used a length of copper wire and fed it into the gap. I should have originally used a smaller diameter splice tubing but I wanna reuse what I have.
Step 2: Making the Fix.
With heat from my propane torch, I applied heat carefully to the joint with filler wire inside. The solder flowed and coated all the copper surface. Once enough had pooled in the joint I turned off the torch and let it cool. Now for the next step!
Step 3: Pulling a Vacuum.
Using my manifold gauges and vacuum pump, I pulled a vacuum for 20 minutes then let it sit for 15 minutes. Once no loss of vacuum was observed, I turned close the service valve on the compressor and it was time to put refrigerant back into the system!
Step 4: Adding R134a Refrigerant.
I disconnected the (yellow) hose to the vacuum pump and hooked it into the R143a can tap. I had the two valves on the manifold closed. Now I made a quarter turn to open the can tap valve and made a 1/8th turn on the blue (low pressure) valve of the manifold. I unscrewed the blue hose at the service valve a bit to let the refrigerant bleed out the trapped air then I fingered tightened the hose onto the service valve.
Now I opened the service valve to let R134a into the system. Once the static pressure reached 5psi, I turned off the manifold blue valve. Now for testing and fine tuning of refrigerant charge!
Step 5: Powering Up Under No Load.
Using a Kill-A-Watt meter, I carefully monitored the power consumption while I turned on the blue valve slightly. My goal is 68Watt power draw with the evaporator in free air and a crankcase temperature of 55C. It is vital not to put too much refrigerant into any system and this risk slugging and destruction of the compressor. Ideally a scale is needed to weigh in the Oz of refrigerant going in but I don't have that. I use the power consumption and case temperature to let me know all is well.
Once I achieved the power level desired, I closed the service valve then closed the manifold blue valve and the can tap valve.
Now to test under load!
Step 6: Load Testing.
Here is where I really fine tune the pressure of refrigerant in the system.
I let her run and adding small volumes of refrigerant until I noticed the following. The compressor surface temperature is 51C in an ambient of 28C. The power consumption is approximately 75watts which is the motor rating.
I'm pleased with my diy fix for the leak!