A refrigerant boils at about seventy-five degrees F at atmospheric pressure. An appliance charged with it falls into which category?
Correct Answer
C) A low-pressure appliance, because its boiling point is above the threshold set for that class
Appliance categories are drawn by where the refrigerant boils at atmospheric pressure. A refrigerant boiling above about fifty degrees F places its appliance in the low-pressure class, which means the machine spends part of its operating cycle below atmospheric pressure and gets a purge unit, a low leak test ceiling and its own recovery level. Seventy-five degrees is well above the line, so this machine would be serviced as a low-pressure appliance.
Why This Is the Correct Answer
The definition of a low-pressure appliance rests on a boiling point above roughly fifty degrees F at atmospheric pressure, which is what makes the machine run in a vacuum at normal temperatures. A refrigerant boiling at seventy-five degrees is clearly above that line, so everything that follows for the low-pressure class applies to an appliance charged with it.
Why the Other Options Are Wrong
Option A: A very high-pressure appliance, because its saturation pressures run above the usual range
Very high-pressure appliances use refrigerants that boil far below zero, so this refrigerant sits at the opposite end of the scale.
Option B: A high-pressure appliance, because it boils above the freezing point of water at atmospheric
The line between the classes is not the freezing point of water. Using thirty-two degrees instead of the actual threshold is a common way to land on the wrong class.
Option D: A small appliance, because refrigerants of this kind are only used in factory sealed units
Appliance size and construction are a separate question from refrigerant class, and nothing about a boiling point implies a factory sealed unit.
Memory Technique
Above fifty and it boils in a warm room, so the machine has to live in a vacuum.
Reference Hint
Low-pressure appliances use refrigerants with a boiling point above about fifty degrees F at atmospheric pressure.
More epa-608-type-3 Questions
Some jobs on a chiller count as a major repair under the refrigerant rules, which changes what a technician is allowed to do with a badly leaking machine. Which job falls into that category?
An owner asks how many pounds of refrigerant the rules allow to be left inside a chiller once the recovery has been signed off. What is the correct answer to give him?
The motor of a hermetic centrifugal chiller sits inside the pressure boundary rather than outside it on a shaft. What follows from that construction?
An oxygen monitor is used to decide whether a chiller machine room is safe to enter after a refrigerant release. Below what oxygen reading is the atmosphere treated as oxygen deficient?
A low-pressure chiller's rupture disc has a discharge line running from it. Where does that line have to terminate?
A refrigerant vapor detector in a chiller machine room reaches its alarm level. Besides sounding, what is that alarm expected to do?
Which piece of equipment requires a technician to hold Type III certification before it may be serviced?
What property of the refrigerant is what actually places an appliance into the low-pressure category?
During normal operation, what condition exists inside the evaporator of a running low-pressure centrifugal chiller?
In what unit is the required final recovery vacuum for a low-pressure appliance normally expressed?
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