My technician (and brother in law) Bert made a good point the day (It’s hard for me to admit it, but it’s true). When he needs to open the refrigerant circuit to make a repair regardless of whether he is recovering or pumping down, he pulls out his nitrogen tank and his regulator (We like the VN500 shown above).
Once the refrigerant has been pumped down or recovered, instead of opening the system to the atmosphere and exposing it to air and moisture, he simply puts it on “BRZ” mode and introduces a very low flow of nitrogen. Now when he cuts into the system to replace a line drier, or a coil, or a compressor, or an accumulator (you get the idea) the system will stay dry and it will be less likely that anything undesirable enters the system. You simply connect the regulator to your center hose and direct the flow to the high side, low side or both depending on what part of the system you have open.
Once the system is all dry fit into place you are then ready to flow nitrogen while brazing, pressure test and even triple evacuate if nitrogen is needed for that.
The biggest hurdle to getting techs to flow nitrogen while brazing is getting the nitrogen tank off the truck. If you get in the habit of connecting nitrogen before you ever cut or open the lines it even further reduces the chance that you “forget” and increases the chances that your system is clean and dry.
Just a thought (from Bert)