A packaged unit has been repaired and evacuated, and its nameplate lists a factory charge by weight. On a mild day with almost no load on the building, what is the most reliable way to put the charge back in?
Correct Answer
C) Weigh in the nameplate charge using a scale under the cylinder
Superheat and subcooling methods need the system running under enough load to give steady readings, and on a mild day with no demand on the building those readings wander. The nameplate charge weighed in with a scale does not depend on conditions at all. It is also the only method that works on a system that has been fully evacuated, since there is no charge in it yet to measure against. Operating checks are made afterward once conditions allow.
Why This Is the Correct Answer
A system that has been evacuated has no charge to measure, and mild weather with no load makes every operating measurement unreliable. Weighing in the amount the nameplate lists puts the correct quantity in regardless of the weather, and it can be documented on the ticket. Once the building has load, superheat or subcooling can be checked to confirm the charge is behaving as expected.
Why the Other Options Are Wrong
Option A: Charge until the suction pressure matches a chart for the outdoor temperature
Suction pressure charts assume a system running under real load. On a mild day with no demand, the pressure that chart calls for will never appear.
Option B: Charge until the sight glass in the liquid line runs clear of bubbles
A clear sight glass shows the liquid line is full, which can happen well before the system holds its full charge on a lightly loaded day.
Option D: Charge until the compressor amperage reaches its rated load value
Compressor amperage tracks load as much as charge. On a mild day the motor will draw well under its rated value with a correct charge in the system.
Memory Technique
No charge, no readings. When there is nothing running, the scale is the only honest instrument on the truck.
Reference Hint
After evacuation, charge by weight to the nameplate value; verify with operating measurements once the system sees load.
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?
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