Hot copper exposed to air grows black copper oxide that flakes off later and plugs screens, metering devices and compressor valves. A trickle of nitrogen, a few cubic feet per hour from a regulator and flowmeter, displaces the oxygen inside the pipe during brazing. Inspectors and manufacturers can tell from cut joints whether it was done, and warranty claims sometimes hinge on it.
Are you flowing nitrogen? Cut that joint open later and I don't want to see a speck of scale.
Also heard as
- flow nitrogen
- nitrogen purge
- purging with nitrogen
Related terms
Sweat
To join copper pipe and fittings with a torch and filler metal drawn into the joint by capillary action.
Filter-drier
A canister of desiccant in the refrigerant line that traps moisture, acid and debris.
Line set
The pair of copper refrigerant lines, one insulated suction line and one smaller liquid line, linking indoor and outdoor units.
Bubble it
To leak-check a joint or fitting by brushing on soap solution and watching for bubbles.