313A Piping, Brazing & Leak Detection 3

Question 1

What is the purpose of an oil trap (inverted P-trap) installed at the base of a vertical refrigerant suction riser?

Accepted Answer

To collect oil that drains down during the off-cycle and return it to the compressor

Answer

To reduce suction line pressure drop across the riser

Answer

To prevent liquid refrigerant from entering the compressor during start-up

Answer

To act as a flow indicator for suction gas velocity

Question 2

What is the maximum recommended refrigerant velocity in a liquid line to prevent flashing ahead of the metering device?

Accepted Answer

3 m/s

Answer

0.5 m/s

Answer

8 m/s

Answer

15 m/s

Question 3

Per the Canadian Refrigeration Code, what is the maximum recommended support spacing for horizontal copper refrigerant suction lines?

Accepted Answer

3 m (10 ft)

Answer

300 mm (12 in)

Answer

1.2 m (4 ft)

Answer

Support is only required at changes of direction

Question 4

Why is reaming the inside of copper tubing after cutting with a wheel cutter a mandatory step?

Accepted Answer

To remove the internal burr that restricts flow and can contaminate the system

Answer

To increase the internal bore diameter for higher refrigerant flow

Answer

To improve brazing alloy adhesion to the tube wall

Answer

To allow the fitting socket to slide freely over the tube end

Question 5

When sizing refrigerant suction lines, the design goal is to:

Accepted Answer

Balance minimum velocity for oil return with minimum pressure drop

Answer

Minimize pipe diameter to reduce the total refrigerant charge

Answer

Use the largest diameter available to reduce compressor amperage

Answer

Match the suction line diameter exactly to the compressor suction port size

Question 6

Outdoor refrigerant line set insulation must be protected primarily against:

Accepted Answer

UV degradation of insulation and mechanical damage from wind-induced vibration

Answer

Elevated internal pressure caused by solar heating of the liquid line

Answer

Condensation forming on the outside of the suction line insulation

Answer

Low ambient temperatures causing the refrigerant to solidify in the line

Question 7

Which type of mechanical fitting is preferred for refrigerant piping connections that must be disassembled for service?

Accepted Answer

SAE 45° flare fittings

Answer

Press-fit (crimped) copper fittings

Answer

Socket-type brazed fittings

Answer

Compression fittings