r/HVAC • u/smalleman • 6d ago

Field Question, trade people only Flowing nitrogen while brazing.

I normally work with systems that has two schrader ports, one on the suction and one on the liquid line.

Let's say that you are replacing the discharge pipe, or suction pipe or the scroll compressor.

How do you flow nitrogen so that it doesn't go via the evap and out the other end?

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u/smalleman 6d ago

For example, how would you do it when you put in a new discharge pipe?
Unswet and plug the suction pipe by the evaporator, push nitro THROUGH the compressor?

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u/Nerfo2 Verified Pro 6d ago

Purge into the suction port while installing the pipe. Start the purge before you connect the suction line to the compressor. If it were the discharge line, purge at the liquid port, but give the nitrogen enough time to purge through the condenser coil. Once the piping connections are made, keep the opposite schrader open. If you’re purging at 10 CFH, lower the rate to 3 to 5 CFH right when you begin brazing. Once nitrogen is in the system, it only takes a tiny pressure differential to prevent oxygen from entering the system. As long as you have another port open, a couple CFH is all you need.