System Charging & Evacuation Flashcards
7 cards from real CFC practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 System Charging & Evacuation flashcards as text
What does a micron gauge reading of 500 microns or below typically confirm during system evacuation?
Answer: The system has achieved an adequate vacuum for most refrigeration applications
A reading of 500 microns or below indicates a deep vacuum sufficient to remove moisture and non-condensables for most HVAC/R applications before charging.
Why should a technician never use a manifold gauge set's sight glass to determine when evacuation is complete?
Answer: Manifold gauges are not accurate enough below 0 psig to measure true vacuum depth
Standard manifold gauges lack the resolution to measure the deep vacuum levels required; an electronic micron gauge is needed to verify adequate evacuation.
When charging by weight, which tool is essential for accuracy?
Answer: Calibrated refrigerant charging scale
A calibrated refrigerant charging scale measures the exact weight of refrigerant transferred into the system as specified by the manufacturer.
What happens to vacuum pump performance if the pump oil becomes contaminated with moisture?
Answer: The pump's ultimate vacuum capability decreases significantly
Water-contaminated vacuum pump oil cannot maintain the required low vapor pressure, degrading the pump's ability to achieve deep vacuum levels.
Which of the following refrigerants requires the technician to charge from the vapor phase only on the low side?
Answer: R-22
R-22 is a single-component (azeotrope-like) refrigerant that can be charged as vapor on the low side without fractionation concerns, making vapor charging standard practice.
A system's low-side pressure rises to suction saturation levels immediately after the vacuum pump is turned off, even after achieving 300 microns. What is the most likely cause?
Answer: There is a leak in the system that is allowing air in
A rapid pressure rise to saturation levels after pump shutoff indicates a leak is allowing air (or refrigerant vapor) into the system rather than outgassing of residual moisture.
EPA regulations require that recovery equipment manufactured after November 15, 1993, must achieve what vacuum level before opening a system or making repairs?
Answer: Levels defined by the equipment's certification standard (ARI 740)
EPA Section 608 requires technicians to recover refrigerant to levels established by ARI Standard 740, which vary by refrigerant type and system size.