EPA 608 609 System Evacuation and Charging Procedures 2 — Questions and Answers
Question 1: How must a blended (zeotropic) refrigerant be added to a system during charging?
- As vapor only through the suction line
- As liquid only (Correct answer)
- Either vapor or liquid — no difference
- As a 50/50 vapor-liquid mix
Correct answer: As liquid only
Zeotropic blends like R-410A and R-404A must be charged as liquid to prevent fractionation, which would alter the blend's composition and performance.
Question 2: What does the blue (low-side) gauge on a manifold gauge set measure?
- High-side discharge pressure
- Low-side suction pressure (Correct answer)
- Refrigerant vapor temperature
- Compressor oil pressure
Correct answer: Low-side suction pressure
The blue gauge measures low-side (suction) pressure, which corresponds to the evaporator pressure and is used to assess evaporator conditions.
Question 3: When charging a single-component refrigerant into an operating system, in what state should it enter the suction line?
- Liquid only
- Vapor (gas) only (Correct answer)
- Solid (dry ice)
- Supercritical fluid
Correct answer: Vapor (gas) only
Single-component refrigerants like R-22 can be safely charged as vapor into the suction line of a running system without risk of slugging the compressor.
Question 4: What does measuring superheat help a technician determine when charging a system with a fixed-orifice metering device?
- System efficiency rating
- Proper refrigerant charge level (Correct answer)
- Compressor oil level
- Filter drier condition
Correct answer: Proper refrigerant charge level
In fixed-orifice systems, suction line superheat directly reflects the refrigerant charge level — too high indicates undercharge, too low indicates overcharge.
Question 5: When using the subcooling method to verify charge in a TXV system, where is the liquid line temperature measured?
- At the evaporator inlet
- At the compressor suction port
- At the liquid line near the condenser outlet (Correct answer)
- At the compressor discharge port
Correct answer: At the liquid line near the condenser outlet
Subcooling is measured at the liquid line leaving the condenser, comparing actual temperature against saturation temperature at the measured high-side pressure.
Question 6: What manifold gauge readings typically indicate an overcharged refrigeration system?
- Both suction and discharge pressures below normal
- Both suction and discharge pressures above normal (Correct answer)
- Low suction and low discharge pressures
- Normal suction pressure with high discharge only
Correct answer: Both suction and discharge pressures above normal
Overcharging floods the evaporator with excess liquid refrigerant, raising suction pressure, while the condenser must reject extra heat, raising discharge pressure.
EPA 608 609 System Evacuation and Charging Procedures 2
How must a blended (zeotropic) refrigerant be added to a system during charging?