Answer:
The correct answer is: technician B, all connection O-rings have to ve replaced when retrofitting a system to R-134a.
Explanation:
When we have a refrigerant line, the refrigerant is used through a refrigeration cycle. Refrigerant should pass in a physical process of transformation, it should be pure, avoid another kind of phenomena.
When we are retrofitting a system to R-134a, it is thus necessary to change all connection O-rings. In that way, we can prevent the refrigerant of crossed contamination with other refrigerants or substances.
Let's analyze the opposite situation, if we do not change the O-rings and we change the refrigerant, probably there will be a few previous substances, which can react, or create other phenomena when they undergo the refrigeration cycle with the R-134 a. We have to avoid this situation.
