HVACR Pipe Soldering Brazing - In HVACR there are two major types of soldering done. Soft Soldering for soldering water pipes and brazing or silver soldering for soldering refrigeration piping. There are various techniques for both types of soldering and everyone develops their own in the field but it is important to follow the basics of soldering when joining the piping together. Following the basics of soldering will ensure success and we all enjoy a successful job completed.

HVACR Pipe Soldering Brazing - Refrigeration Systems

Soldering Pipe with Leaking Valves

Every plumber and many HVAC technicians have had the privilege and frustration of attempting to solder a copper water pipe that has a leaking valve which prevents the complete shut off of water flow. These plumbers and technicians know it is impossible to solder copper water pipes that have water in them or flowing through it. The water has to be drained from the pipe and the pipe must be dry and clean before soldering can begin. So if we have a valve that won’t hold the water back or even piping systems with water shut off valves but have piping running up multiple levels with no isolation and the water keeps migrating back to where you want to solder, how do we keep the water from the location where we are soldering?

The Bread Trick

Plumbers and HVAC Technicians have used this age old proven method to stop the flow of water where they want to solder. Simply take some white bread, remove the crust, and roll the bread into a ball as appropriate to the size of the pipe. Stuff this ball into the pipe where the water is coming from and solder the joint. The bread holds the water back while the soldering is being done. After the soldering job is done and the water flow restored the ball of bread will dissolve and complete water flow restored especially after the strainers are cleaned. Don’t forget to clean the strainers if the system is equipped with strainers. This does not work when the pipe is under extreme pressure.

Pipe Freezing Machines

HVACR Pipe Soldering Brazing

HVACR Pipe Soldering Brazing – Another method for stopping the flow of water if a valve is broken is the pipe freezing machine. This method is far more expensive than the bread trick but it works flawlessly. Simply clamp some refrigeration heads to the pipe in question and turn on the machine. Spray some water on the refrigeration head and wait the recommended time required by the manufacturer of the pipe freeze machine. Then perform the soldering job and unhook the machine when finished. The ice inside the pipe will melt and the flow of water will be restored. The water pipe freezing machine is a good way to solder pipe where it is otherwise impossible to shut off water flow.

Brazing and Soldering Copper HVACR Pipe

Refrigeration piping is always brazed as brazing makes a very solid leak free joint that withstands high and low temperatures and pressures. Brazing is done with oxyacetylene for refrigeration and the oxyacetylene tanks should have pressure regulators for regulating proper pressures when brazing. When soldering refrigeration pipe it is best to use solder which has a composition of silver in it as the silver bounds with the copper and makes for an excellent leak free strong joint (capillary attraction).

Very High Temperature – Brazing

Brazing in HVAC is done with oxyacetylene torches which heat the pipe to temperatures approaching 6,000° F. It is important to note that all safety precautions should applied when brazing HVAC pipes including safety glasses and fire extinguishing equipment. Safety is always first when doing any job in HVAC and especially when dealing with oxyacetylene equipment and brazing.

Clean & Flux with Any Type of Soldering

Before brazing or soldering any pipe it is important to fit the pipe and clean it. This brazing setup will ensure the job is done correctly. Cut the pipe to the desired length with tubing cutters and ensure it has a good fit. After checking the fit and proper length clean the area where the pipe is to be soldered. After cleaning apply flux to the inner and outer joints. Using a nitrogen bottle with a very slight flow of nitrogen allow the nitrogen to flood the pipe flushing any oxygen from the pipe. Maintain a slight flow of nitrogen in the open refrigeration circuit until you are ready to perform a triple refrigeration evacuation. The nitrogen prevents oxidation inside the refrigeration piping.

It is important to apply the heat evenly across the joint and heat the pipe before applying the solder. After the pipe has been heated apply the solder to the joint and allow it melt into the joint. Do not use the torch to heat the solder but use the heat on the pipe to melt the solder evenly. If done properly the solder will seemingly be sucked into the joint. That is called capillary attraction and is the target or desired goal of soldering or brazing. Do not use too much solder because the solder can migrate inside the pipe and cause a blockage of the pipe or little beads of solder may form inside the pipe and these little beads of solder will migrate through the refrigeration system and plug screens, metering devices, and possibly damage the compressor.

The Nitrogen Pressure Test – HVACR Pipe Soldering Brazing

After the pipe is soldered and complete apply a wet rag or water to joint and thoroughly inspect the joint for even solder around and inside the joint. Use a mirror for difficult-to-see joints. After inspection is complete and you are satisfied that all solder joints are completely sealed perform a pressure test with nitrogen to check for leaks. Use soap bubbles when the pipe is pressurized and look for bubbles around the newly brazed joint. Also, watch the pressure gauge for a drop in pressure. A drop in pressure after applying the nitrogen surely means there is a leak in the system which needs to be found and repaired.

Oxidation is an Enemy in Refrigeration – HVACR Pipe Soldering Brazing

Oxidation is an enemy to refrigeration systems and piping. Oxidation causes many problems with refrigeration systems and piping. To prevent oxidation when brazing refrigeration piping do not forget the slight amount of nitrogen in the system while brazing. It is important to only allow a slight amount of nitrogen into the system. Too much nitrogen pressure and the nitrogen pressure will not allow a good seal of the solder inside the pipe joint but push it out creating a tiny hole.

Other references can be found here for soldering and brazing.

HVACR Pipe Soldering Brazing - Refrigeration Systems

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HVACR Pipe Soldering Brazing - Refrigeration Systems

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