Low-Pressure Appliance Scope — EPA 608 Practice Questions

31 questions · 25% of the Type III — Low Pressure exam

Worked questions

1. Which piece of equipment requires a technician to hold Type III certification before it may be serviced?

A centrifugal chiller charged with R-123
BA packaged rooftop unit charged with R-410A
R-410A operates at high pressure, well above atmospheric on both sides of the system. Rooftop packaged units are high-pressure appliances and are covered by Type II certification, not Type III.
CA factory-sealed window air conditioner holding three pounds of refrigerant
A factory-sealed window unit holding a small charge is a small appliance. Small appliances holding five pounds or less and charged at the factory are Type I work, regardless of which refrigerant they contain.
DAn ultra-low-temperature laboratory freezer charged with R-13
R-13 is a very high-pressure refrigerant used in cascade and ultra-low-temperature systems. Very high-pressure appliances are grouped with high-pressure work under Type II certification, so this is not a Type III machine.

Why A is correct

R-123 is a low-pressure refrigerant used almost exclusively in centrifugal chillers, and any appliance charged with it is a low-pressure appliance. Servicing, recovering from, or disposing of that machine is Type III work. A technician needs either Type III or Universal certification to open the machine or connect recovery equipment to it.

What this question is testing

This item checks whether the candidate can sort real equipment into the four certification buckets by refrigerant and pressure class instead of by size or by how the machine looks. It rewards knowing that low pressure means the refrigerant, not the horsepower.

On the job

Chiller plants in hospitals, universities, and older office towers still run R-123 centrifugals, and those machines are usually maintained by a specialty contractor. If a shop sends a Type II tech to break into one, the shop is out of compliance and the tech is working on equipment they were never trained to handle. Most chiller mechanics carry Universal certification for exactly this reason, because a single plant may hold a low-pressure centrifugal, high-pressure screw chillers, and small package units side by side.

Memory technique

Three ones, three number classics: R-11, R-113, R-123 all start with 11 or 12 and all mean Type III.

Exam tip

Match the refrigerant first: R-11, R-113, and R-123 point to Type III every time. Big physical size alone does not make a machine low pressure.

Where to look it up

Certification categories are set out in 40 CFR 82.161; Type III is the low-pressure appliance category.

2. A chiller charged with R-123 has been shut down long enough to warm to a room temperature of about seventy degrees F. What does a gauge on the machine show?

ARoughly seventy psig, since gauge pressure tracks the room temperature in degrees on a warm day
Gauge pressure does not track room temperature in degrees, and the two numbers matching is a coincidence being read as a rule. Seventy psig would be an idle reading for a high-pressure refrigerant, not for this family.
BRoughly thirty psig, the same reading an idle R-22 system would give sitting in that same room
Thirty psig is a believable idle reading for a high-pressure system, which is exactly why it is offered here. A low-pressure refrigerant cannot build that much pressure at room temperature no matter how long it sits.
A slight vacuum, because the refrigerant's saturation pressure at that temperature is below atmospheric
DExactly atmospheric pressure, because a machine standing idle this long has equalized with the room around it
The machine is sealed, so it never equalizes with the room however long it stands. Its pressure is set by the saturation temperature of the refrigerant inside, which at this temperature is below atmospheric.

Why C is correct

Saturation pressure tracks temperature. With R-123 at seventy degrees F, the corresponding pressure is below fourteen and seven tenths psia, so a gauge referenced to atmosphere reads on the vacuum side. The machine is not equalized with the room because it is a closed vessel; it holds whatever pressure its refrigerant temperature dictates.

What this question is testing

This checks that you can apply the pressure temperature relationship to a low-pressure refrigerant and predict what a gauge will show. It also tests whether you understand why these machines take in air even while sitting idle. Applying saturation data to an idle machine is a step beyond reciting the definition, so the item measures working command of the pressure temperature relationship.

On the job

This is a daily judgment call. You walk up to an idle machine, see the gauge sitting in a vacuum, and have to decide whether the machine is normal or has lost its charge. On a low-pressure chiller a slight vacuum at room temperature is exactly right. The same reading on an R-134a machine would mean the charge is gone. Knowing which is which keeps you from condemning a healthy machine or from ignoring a real loss of charge.

Memory technique

Room cooler than the boiling point means the gauge goes negative. Boiling point is the tipping line.

Exam tip

Compare the refrigerant's boiling point to the temperature in the question. Below the boiling point means vacuum, above it means slight positive pressure.

Where to look it up

R-123 boils in the low eighties F at atmospheric pressure, so below that temperature the machine sits in a vacuum.

3. A stationary engineer starts and stops a low-pressure chiller, records its gauge readings and adjusts its water temperature setpoint, but never connects to the refrigerant circuit. What does the certification requirement mean for that person?

AType III certification is required, because the person is operating a low-pressure appliance
Operating an appliance is not service on it. The requirement attaches to work that could release refrigerant.
BUniversal certification is required, because plant operators work on more than one machine
Universal certification simply covers all three appliance classes. Working around several machines does not by itself require any certification.
No certification is required, because the work cannot be expected to release refrigerant
DType II certification is required, because gauge readings involve the high pressure side
Reading a gauge releases nothing, and the certification type follows the appliance rather than which side of the machine a reading comes from.

Why C is correct

The rule follows the possibility of a release. Operating a machine from its control panel and logging readings does not open the refrigerant circuit and cannot release refrigerant, so no certification is required for that work. Certification becomes necessary as soon as the person begins service that could release refrigerant.

What this question is testing

This tests the definition of the regulated activity. The exam checks whether the candidate ties the requirement to potential release rather than to job title or proximity to the equipment.

On the job

Large plants usually certify their operating engineers regardless, because the line between operating and servicing gets crossed constantly: an engineer who drains the purge separator or changes a filter has moved onto the other side of it. Contractors find it useful to ask early who on site is certified, since it determines who can help with a recovery and who has to stand back and watch.

Memory technique

Turning a knob is operating. Turning a wrench on the circuit is servicing.

Exam tip

Certification follows work that could release refrigerant. Running the machine and writing the log is not that work.

Where to look it up

Technician certification is required for maintenance, service or repair that could reasonably be expected to release refrigerant.

28 more in the bank

Answers and explanations for these are in the app.

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?
Which refrigerant was the original factory charge in most low-pressure centrifugal chillers built during the nineteen sixties and seventies?
A running low-pressure chiller develops an opening in a section of shell that is below atmospheric pressure. What passes through that opening?
A technician is assigned to recover the charge from a large water chiller holding nine hundred pounds of R-134a. Which certification does that job require?
Into which appliance category does a machine charged with R-13 for very low temperature service fall?
Two chillers in the same plant are both charged with R-123, one holding two hundred pounds and one holding two thousand pounds. How are the two machines classified?
A low-pressure chiller is clearly losing charge over the season, yet a sensitive leak detector finds nothing around the machine while it runs. What best explains this?
Which single certification lets a technician service both an R-11 centrifugal chiller and the building's R-410A rooftop units?
A technician holds Type II certification only. Which assignment may that technician legally carry out without earning another certification?
An older centrifugal chiller is converted from R-11 to R-123. What happens to the certification a technician needs to service it afterward?
On a low-pressure centrifugal chiller running at load, how do the evaporator and condenser sit relative to atmospheric pressure?
What does holding Type III certification allow a technician to do when buying refrigerant from a supplier?
Liquid refrigerant has to move from the condenser back to the evaporator inside a low-pressure centrifugal chiller. Which device controls that flow?
The float valve on a low-pressure centrifugal chiller has stuck in the open position. What does the machine do as a result?
A low-pressure chiller that has been shut down for months keeps a heater energized in its compressor oil sump. What is that heater for?
A helper is sent to add refrigerant to an R-123 centrifugal chiller that is running low, and nothing else is to be touched. What certification does that task require?
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 idle R-123 chiller sitting in a very hot machine room shows a small positive pressure on its gauge rather than the usual vacuum. How is that machine classified?
A machine room housing an R-123 chiller has to have mechanical ventilation and a refrigerant vapor detector. Which body of requirements is the source of those provisions?
A technician arrives at a machine he has not worked on before and needs to know which certification and which procedures apply. What does the machine's nameplate provide?
A building owner is relocating a working R-123 chiller to another property that the same owner controls. What has to happen to the charge before the machine is disconnected?
A chiller's oil sump and oil cooler are being opened for a rebuild. How do those components stand in relation to the refrigerant circuit?
A centrifugal compressor works differently from the reciprocating and scroll compressors used on high-pressure equipment. How does it raise the pressure of the vapor?
A centrifugal chiller with a known air leak begins surging on hot afternoons but runs normally on mild days. What connects the non-condensable gas to the surging?
A refrigerant boils at about seventy-five degrees F at atmospheric pressure. An appliance charged with it falls into which category?
A chiller's rupture disc has to be replaced after it relieved. What does that job require before the disc comes off?
A laboratory has a small factory sealed packaged chiller holding four pounds of R-134a. Which certification covers service on that unit?

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Low-Pressure Appliance Scope — EPA 608 Practice Questions

Worked questions

1. Which piece of equipment requires a technician to hold Type III certification before it may be serviced?

2. A chiller charged with R-123 has been shut down long enough to warm to a room temperature of about seventy degrees F. What does a gauge on the machine show?

3. A stationary engineer starts and stops a low-pressure chiller, records its gauge readings and adjusts its water temperature setpoint, but never connects to the refrigerant circuit. What does the certification requirement mean for that person?

28 more in the bank

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