313A Piping, Brazing & Leak Detection

Question 1

When brazing copper-to-copper refrigerant joints, which brazing alloy is most commonly specified?

Accepted Answer

BCuP-5 (15% silver, copper-phosphorus)

Answer

BCuP-5 (15% silver) is the industry standard for copper-to-copper refrigerant joints because it is self-fluxing on copper and flows reliably at brazing temperatures.

Question 2

Why must dry nitrogen be purged through copper tubing during the brazing process?

Accepted Answer

To prevent cupric oxide scale from forming inside the pipe

Answer

Flowing dry nitrogen displaces oxygen inside the pipe, preventing the formation of copper oxide scale that can contaminate compressor valves and metering devices.

Question 3

What is the minimum recommended overlap length for a brazed socket joint in refrigerant copper tubing?

Accepted Answer

Equal to the tube outside diameter

Answer

The minimum overlap for a brazed socket joint should equal the tube outside diameter to provide adequate joint strength and a leak-free seal.

Question 4

When cutting copper refrigerant tubing, which tool provides the cleanest cut with the least internal deformation?

Accepted Answer

Wheel-type tubing cutter

Answer

A wheel-type tubing cutter produces a clean, square cut with only a small internal burr that is easily removed by reaming, while saws leave rough edges and metal filings.

Question 5

What is the primary hazard when brazing refrigerant lines that have not been fully purged of refrigerant vapour?

Accepted Answer

Phosgene gas can form from refrigerant decomposition in the flame

Answer

Residual refrigerant or oil vapour exposed to an open flame can decompose into phosgene, an acutely toxic gas, making complete purging and ventilation critical before brazing.

Red Seal HVAC 313A Practice Test

Red Seal HVAC 313A Practice Test

313A Piping, Brazing & Leak Detection