System Evacuation and Charging Procedures Flashcards

What is the primary purpose of evacuating a refrigeration system before charging with refrigerant?

Answer: To remove moisture and non-condensable gases

Evacuation removes moisture and non-condensable gases such as air and nitrogen that would degrade system performance and damage components.

What instrument is used to measure the depth of vacuum during system evacuation?

Answer: Micron gauge (electronic vacuum gauge)

An electronic micron gauge measures vacuum in microns of mercury (µmHg), providing accurate readings below the range of standard manifold gauges.

What vacuum level in microns must be achieved before charging most residential HVAC systems per industry standards?

Answer: 500 microns

AHRI and most manufacturers specify that systems must be evacuated to 500 microns or below before refrigerant charging to ensure adequate moisture removal.

What should a technician investigate if the vacuum rises rapidly above 1,000 microns immediately after isolating the vacuum pump?

Answer: A system leak or residual moisture

A rapid rise in micron level after isolation indicates either a leak allowing air entry or moisture still boiling off inside the system.

Why should a technician evacuate from both the high and low sides of a refrigeration system?

Answer: To achieve faster and more thorough evacuation past any closed internal valves

Evacuating from both service ports removes non-condensables and moisture more quickly and ensures no section of the system is isolated from the vacuum.

What type of oil must be used in vacuum pumps designed for HVAC/R refrigerant work?

Answer: Dedicated vacuum pump oil

Vacuum pump oil is specially formulated to maintain low vapor pressure and absorb moisture without breaking down, which standard lubricants cannot do.