A system charged with a zeotropic blend has lost most of its charge through a large leak, and the leak has now been repaired. What should be done with the small amount of refrigerant still in the system?
Correct Answer
B) Recover it, then evacuate and weigh in a full charge of fresh blend
When a blend leaks slowly as vapor, the lighter components leave first and what remains in the system is no longer the mixture printed on the nameplate. Topping that up with fresh blend gives a charge whose composition nobody can state, and the system will not perform to its ratings. The clean fix is to recover what is left, pull the system down, and weigh in a full charge of the correct product.
Why This Is the Correct Answer
A large vapor leak fractionates a zeotropic blend, so the refrigerant left in the system is enriched in the heavier components. Adding fresh blend on top of it produces a mixture of unknown composition with the wrong pressure and temperature behavior. Recovering the remainder and weighing in a complete fresh charge is the only way to get the system back to a known refrigerant at a known weight.
Why the Other Options Are Wrong
Option A: Leave it in place and add fresh blend until the nameplate weight is reached
Topping off works with a single-component refrigerant. On a blend that has lost most of its charge as vapor, it produces a mixture that matches no published data.
Option C: Leave it in place and add only the heavier component of the blend
Blend components are not sold separately and no technician may compound one in the field. Trying to correct composition by addition is not a service practice.
Option D: Recover it and return it to this same system once the repair is verified
Returning the remainder to the same appliance is permitted in general, but this particular remainder is no longer the labelled product, so it would carry the problem back in.
Memory Technique
A blend that has bled off is a recipe with ingredients missing. You cannot fix a recipe by pouring in more of the finished dish.
Reference Hint
Zeotropic blends fractionate during a vapor leak, so a large loss calls for full recovery and a fresh weighed charge.
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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