EPA 609 MVAC System Components & Operation 3

Question 1

What does 'superheat' refer to in MVAC system diagnostics?

Accepted Answer

The temperature of refrigerant vapor above its boiling point at a given pressure

Answer

Superheat is the additional heat absorbed by refrigerant vapor above its boiling point at the evaporator outlet pressure.

Question 2

What does 'subcooling' measure in an MVAC system?

Accepted Answer

How much the liquid refrigerant is cooled below its condensing temperature at high-side pressure

Answer

Subcooling measures how far below its condensing temperature the liquid refrigerant has been cooled, indicating whether the condenser is properly removing heat.

Question 3

What component prevents compressor damage by shutting off the system when pressure is too low or too high?

Accepted Answer

Pressure switches (low-pressure and high-pressure cutout switches)

Answer

Pressure cutout switches protect the compressor by disengaging the clutch if system pressure falls outside safe operating limits.

Question 4

When retrofitting an R-12 system to R-134a, which component should always be replaced?

Accepted Answer

The receiver-drier or accumulator

Answer

The receiver-drier or accumulator must be replaced during retrofit because its desiccant may be saturated and incompatible with R-134a.

Question 5

What is the purpose of an MVAC system accumulator (used with orifice tube systems)?

Accepted Answer

To store excess liquid refrigerant and separate liquid from vapor on the low side

Answer

The accumulator is located on the low-pressure suction side and prevents liquid refrigerant from reaching the compressor, which could cause damage.

EPA 609 - EPA Section 609 Refrigerant Certification Practice Test

EPA 609 - EPA Section 609 Refrigerant Certification Practice Test

EPA 609 MVAC System Components & Operation 3