A technician reaches the target vacuum, isolates the pump, and confirms that the reading holds steady for several minutes. What is the correct next step?
Correct Answer
D) Break the vacuum by admitting refrigerant into the system, keeping air out entirely
A system that has just been proven dry and tight should never see atmosphere again. The vacuum is broken with the refrigerant itself, usually by admitting liquid into the high side through a charging hose that has already been purged, so the first thing entering the system is the product that belongs there. Letting air in undoes the evacuation. Leaving nitrogen in the system leaves a non-condensable behind that will raise head pressure and reduce capacity for the life of the charge.
Why This Is the Correct Answer
Charging into the vacuum means the system goes straight from evacuated to charged with nothing else admitted. Air brings moisture and non-condensables, and both cause the exact problems the evacuation was performed to prevent, so refrigerant is the only acceptable thing to break the vacuum with.
Why the Other Options Are Wrong
Option A: Open the system briefly to atmosphere so pressures equalize before charging begins
Opening to atmosphere admits air and water vapor and throws away the entire evacuation. There is no reason to equalize pressure before charging.
Option B: Break the vacuum with dry nitrogen and then charge refrigerant on top of the nitrogen
Nitrogen is a non-condensable. Left in a charged system it collects in the condenser, raises head pressure and cuts capacity, and it cannot be removed without recovering and re-evacuating.
Option C: Start the compressor and charge vapor directly into the discharge line
Starting a compressor on an empty system risks running it with no cooling and no oil return, and charging into the discharge line is not how a system is brought up from vacuum.
Memory Technique
Nothing but refrigerant follows a good vacuum. Air and nitrogen are both trespassers at charging time.
Reference Hint
40 CFR 82.156 requires evacuation before service; industry practice is to break the vacuum with refrigerant so no air or non-condensables re-enter.
More epa-608-type-2 Questions
A walk-in cooler condensing unit holds a full charge of twenty-five pounds of R-404A, which is below the fifty pound threshold that brings an appliance under the leak repair provisions. What still applies to this unit?
An office building has thirty water source heat pumps on a common water loop, and each one left the factory assembled, hermetically sealed and charged with four pounds of R-410A. How is one of those units classified?
A data sheet for an unfamiliar refrigerant lists a boiling point of about fifty-five degrees Fahrenheit at atmospheric pressure. What does that tell a technician holding Core and Type II certification?
A technician holds Core, Type I and Type III certification and is sent to recover the charge from a twenty ton rooftop unit charged with R-410A. What does that combination of sections allow on this job?
A fleet garage technician holds only the vehicle air conditioning certification issued under Section 609 and is asked to recover the charge from the shop's own rooftop air conditioner. What does that credential allow?
A split system's outdoor unit, indoor coil and the line set the installer ran and brazed between them are being considered. For the purposes of the refrigerant rules, what makes up the appliance here?
On a new installation the line set is brazed to a factory charged outdoor unit and an indoor coil shipped under a nitrogen holding charge, with the outdoor unit's service valves still closed. What does the recovery requirement call for before that brazing?
A rooftop unit's data plate has weathered until the charge figure cannot be read, and the technician needs the full charge to place the appliance under the evacuation and leak provisions. Where should that figure come from?
A computer room air conditioning unit holds forty pounds of R-407C and connects to a remote air cooled condenser through refrigerant piping run and brazed by the installer. How is that unit classified?
A shop's office manager, who holds no technician certification, is sent to a supply house to pick up a new recovery machine for the commercial crew. What does the sales restriction require at that counter?
People Also Study
Business & Financial Management
120 questions · 70% to pass
Contract Administration
60 questions · 70% to pass
Project Management
60 questions · 70% to pass
Related Study Resources
Previous Question
A technician recovers the charge from a system whose compressor suffered a motor burnout. What should happen to that recovered refrigerant?
Next Question
A technician is out of nitrogen and considers using the oxygen cylinder from the torch outfit to pressurize a system for a leak search. Why must that never be done?