Question

1. During HFC-134a refrigerant recovery, when gauge readings indicate pressure in an A/C system after a 5 minute pause since the system was drawn into a vacuum, you should:
A. Repeat the recovery process
B. Wait overnight, then add refrigerant
C. Flush the system with ester oil
D. Vent the remaining refrigerant

2. Why are shut-off valves located within 12 inches from the “vehicle ends” of A/C service equipment hoses?

A. To keep out contamination
B. To reduce pressure blow-back
C. To stop venting ozone
D. To minimize venting of refrigerant

3. If an HFC-134a A/C system still has pressure after the first refrigerant recovery process is complete (including the five-minute pause), additional recovery necessary until the system vacuum level remains stable for:
A.30 seconds
B. 2 minuets
C. 5 minutes
D. 10 minutes

4. Which of the following statements is correct about flushing A/C systems?
A. Most A/C system manufacturers recommend flushing
B. A/C system flushing effectively cleans very small refrigerant passages
C. Flushing chemicals make refrigerant cool better
D. Flushing solvents may remain in A/C systems, causing problems

5. HFO-1234yf is classified as “A2L-mildly flammable.” This means :
A. It smells like ammonia
B. It is highly explosive, like gasoline
C. It can ignite under certain circumstances
D. It will not ignite

Answer 1

1) -----(A) Repeat the recovery process until the A/C systems holds stable vacuum.

2)-----(D) To minimize venting of refrigerant

Because refrigerant is used in heat pump and refrigeration cycle. Continuous cycle of refrigeration it experiences stage advances from a fluid to a gas and back once more.

3)-----(B) 2 minutes

4)----(B) A/C system flushing effectively cleans very small refrigerant passages

because very small refrigerant contamination can cause restriction and problems for a good function of the compressor.

5)-----(C) It can ignite under certain circumstances

Because in a report of Honeywell claimed that 'HFO-1234yf is very difficult to ignite with electric spark in the range of temperature 500 ⁰C - 900 ⁰C. Ignition was only seen when HFO-1234yf is mixed with PAG at the temperature > 900 ⁰C.