F-Gas English Low GWP
All questions
HFC | Flammable | CO₂ | NH₃
Easy questions |
Medium questions |
Difficult questions
1
Difficult
What additional protective equipment will you use when brazing systems containing HC refrigerants?
| Ear defenders |
| Latex gloves |
| A high-visibility vest |
| A flammable gas detector |
2
Difficult
Why can’t a sealed high-pressure switch be replaced with a standard mechanical one in a system containing a flammable refrigerant?
| It is a potential source of ignition |
| The pressure switch setting will not be correct |
| Dust and moisture may enter |
| There is a risk of refrigerant leakage |
3
Difficult
What is the minimum (recommended) distance from a work area with HC refrigerants within which there must be no sources of ignition?
| 1 m |
| 0.5 m |
| 2 m |
| 3 m |
4
Difficult
What is the maximum safe R32 fill of a recovery cylinder approved for flammable gas that holds 20 kg of R410A (the liquid density of R32 is about 8-10% lower)?
| 20 kg |
| 9 kg |
| 18 kg |
| 33 kg |
5
Difficult
What is the maximum charge of an A3 refrigerant for a hermetic display cabinet with an integral condenser located in the ground-floor sales area of a supermarket?
| 10 kg |
| 0,494 kg |
| 2.5 kg |
| 1.0 kg |
6
Difficult
How can a vacuum pump be used safely to evacuate a system containing a flammable refrigerant?
| Position the pump at least 3 m above floor level |
| Ignition-source-free pump, good ventilation, exhaust to a safe place |
| Place the pump directly on the floor, as low as possible |
| Such systems need not be evacuated before charging |
7
Difficult
What safety measure must you carry in your vehicle when transporting flammable refrigerant cylinders?
| A fire extinguisher |
| A fire blanket |
| Tinted safety goggles |
| Thick gloves |
8
Difficult
How would you prepare a 10 kg R32 water chiller located outdoors for debrazing its joints?
| Recover the R32 to a vacuum, then fill the system with nitrogen to a slight positive pressure (approx. 0.1 bar g) |
| Vent the R32 outdoors and purge the system |
| Recover the R32 to a vacuum and start desoldering immediately |
| Vent the R32 outdoors, then fill and vent the system with nitrogen three times |
9
Difficult
Which of the following leak detection methods should NOT be used to locate an HC refrigerant leak?
| Leak detection foam |
| Electronic leak detector for flammable refrigerants |
| Electronic HFC leak detector |
| Soapy water solution |
10
Difficult
What is the most important difference between a flammable refrigerant recovery unit and a standard one?
| A different colour for the station |
| Different low-pressure switch setting |
| A flammable refrigerant recovery unit has no ignition sources |
| Different connection sizes |
11
Difficult
Which of the following is a source of ignition?
| A contactor (sparking contacts) |
| A sealed NTC temperature sensor |
| An 'n'-type (non-sparking) thermostat |
| An Ex-certified fan motor |
12
Difficult
What particularly hazardous substance is formed when R32 burns?
| Phosgene |
| Hydrogen chloride (HCl) |
| Hydrogen fluoride (HF) |
| Sulphur dioxide (SO₂) |
13
Difficult
What type of refrigerant is R1234ze(E)?
| CFC (chlorofluorocarbon) |
| HFO (hydrofluoroolefin) |
| HC (hydrocarbon) |
| HCFC (hydrochlorofluorocarbon) |
14
Difficult
What hazards does a safety group A3 refrigerant pose?
| Lower toxicity, moderate flammability |
| Higher toxicity, moderate flammability |
| Higher toxicity, higher flammability |
| Lower toxicity, higher flammability |
15
Difficult
According to EN 378, what is the maximum R290 charge in a cold room measuring 5 m × 3 m × 2.5 m (LFL of R290 = 0.038 kg/m³, access category a, location class I, no additional measures))?
| 1.5 kg |
| 4.93 kg |
| 0.285 kg |
| 1.0 kg |
16
Difficult
What is the approximate ratio of the volumetric cooling capacity of R32 to that of R410A (same compressor and conditions)?
| approx. 1.3 |
| approx. 0.75 |
| approx. 0.6 |
| approx. 1.05–1.1 |
17
Difficult
Why are Ex-certified evaporator fan motors used in some systems with flammable refrigerants?
| Because they must be kept running continuously to disperse the leaking refrigerant |
| Because they are more energy-efficient |
| To avoid a source of ignition in the event of a flammable refrigerant leak |
| Because they are more reliable |
18
Difficult
Why is the density difference between HC and HFC refrigerants important?
| Because HCs operate at much higher pressures |
| Because HCs must be charged much more slowly than HFCs |
| Because it determines the system's energy efficiency |
| An HC charge in kg is roughly half that of an HFC |
19
Difficult
What is the GWP of R290 according to Annex VI to Regulation (EU) 2024/573?
| 7 |
| 0.02 |
| 150 |
| 675 |
20
Difficult
Which of the following is NOT a source of ignition?
| An electrical switch |
| An Ex-certified fan motor |
| A light switch |
| An unsealed mechanical pressure switch |
21
Difficult
What is R290?
| Butane |
| Isobutane |
| Propane |
| Propene (Propylene) |
22
Difficult
What is the maximum A2L charge for a hermetic display cabinet with integral condenser in the ground-floor sales area of a supermarket?
| 150 g |
| 2.5 kg |
| 1.2 kg |
| 1.5 kg |
23
Difficult
Why can’t a standard relay be fitted when retrofitting a compressor’s electrical system for flammable refrigerants?
| It could be a source of ignition |
| A relay is never required for compressors using flammable refrigerants |
| The method of starting the compressor motor differs from that used with HFCs |
| Current consumption differs for compressors using flammable refrigerants compared to those using HFCs |
24
Difficult
What is the minimum (recommended) distance from a work area with HC refrigerants within which there must be no ignition sources?
| 1 m |
| 5 m |
| 10 m |
| 3 m |
25
Difficult
A recovery cylinder holds 10 kg of R404A (filling ratio 0.82 kg/l). What is the maximum R290 charge for this cylinder (propane filling ratio 0.43 kg/l per ADR P200)?
| approx. 5.2 kg |
| approx. 17 kg |
| 20 kg |
| approx. 8 kg |
26
Difficult
How can a vacuum pump be used safely to evacuate a system containing R290?
| Ignition-source-free pump, good ventilation, exhaust to a safe place |
| R290 systems need not be evacuated before charging |
| Place the pump directly on the floor, as low as possible |
| Position the pump at least 3 m above floor level |
27
Difficult
Under ADR, what equipment must you carry in your vehicle when transporting flammable refrigerant cylinders (under the 1.1.3.6 exemption)?
| Thick gloves |
| A fire blanket |
| Tinted safety goggles |
| A fire extinguisher (at least 2 kg dry powder) |
28
Difficult
How do you make sure it is safe to light the torch for desoldering joints in a system from which a flammable refrigerant has been removed?
| Such joints must never be desoldered; they must be cut with a pipe cutter |
| Working outdoors is sufficient |
| Ensure good ventilation and check the work area with a flammable gas detector |
| Purge the system with compressed air |
29
Difficult
How would you prepare a system containing 100 g of R1270 for debrazing, if local regulations allow controlled venting of small HC quantities?
| Vent the R1270 to a safe outdoor location, then purge with OFN three times (pressurise and vent), and braze with OFN flowing |
| Recover the R1270 to a vacuum and start brazing immediately without a nitrogen purge |
| Vent the R1270 outdoors and start brazing immediately |
| Vent the R1270 into the room and open a window |
30
Difficult
Which method should NOT be used to locate an R290 leak?
| An electronic leak detector designed for HFCs |
| Leak detection foam |
| Fluorescent dye and UV lamp (if approved by the manufacturer) |
| An electronic detector for flammable refrigerants |
31
Difficult
Why can’t recovery stations designed for HFCs be used with R600a?
| The low-pressure switch setting will not be suitable for R600a due to its lower operating pressure |
| The recovery unit cannot withstand the working pressure of R600a |
| They contain ignition sources |
| The oil in the recovery unit is not soluble in R600a |
32
Difficult
According to EN 378, what is the maximum R1234ze(E) charge in a cold room measuring 5 m × 3 m × 2.5 m (LFL = 0.303 kg/m³, access category a, location class I, no additional measures)?
| 2.27 kg |
| 618 kg |
| 6.18 kg |
| 227 kg |
33
Difficult
What type of refrigerant is R32?
| Hydrofluoroolefin |
| Hydrocarbon |
| Hydrofluorocarbon |
| Carbon dioxide |
34
Difficult
What hazards do A2L refrigerants pose?
| Lower toxicity, lower flammability (burning velocity ≤ 10 cm/s) |
| Higher toxicity, higher flammability |
| Higher toxicity, lower flammability |
| Lower toxicity, higher flammability |
35
Difficult
What hazard is associated with the combustion of HFO or HFC refrigerants?
| Ozone is formed |
| Phosgene is formed |
| Hydrogen fluoride (HF) is formed |
| Nitrous oxide is formed |
36
Difficult
Approximately what compressor displacement is required for R600a compared with R134a for the same cooling capacity?
| The same |
| About seven times as large |
| About twice as large |
| About half |
37
Difficult
What is the GWP value for R32 according to Regulation (EU) 2024/573?
| 0 |
| 7 |
| 675 |
| 3 |
38
Difficult
Why is charge accuracy more important in critically charged R290 systems than in HFC systems?
| Because R290 is only used in systems below 150 g |
| Because such systems never have liquid receivers |
| Because of lower operating pressures |
| The charge mass is much smaller than in an HFC system, because the liquid density of R290 is much lower |
39
Difficult
Why does the condenser fan run continuously in some systems using R1270?
| To prevent the build-up of contaminants in the condenser |
| To ensure that the discharge pressure never becomes excessive |
| To dilute the refrigerant in the event of a leak |
| To reduce energy consumption |
40
Difficult
What is the role of a suction liquid separator (also in systems with flammable or toxic refrigerants)?
| It separates liquid from oil |
| It heats the refrigerant before the evaporator |
| It is used only to measure moisture |
| It prevents liquid refrigerant from entering the compressor |
41
Difficult
What is the function of an oil separator in systems using flammable or toxic refrigerants?
| Heats the refrigerant before it enters the evaporator |
| They are used solely to measure the moisture content of the refrigerant |
| It prevents liquid from entering the compressor |
| Separates oil from the refrigerant and facilitates the return of oil to the compressor |
42
Difficult
Why do liquid and oil separators in CO₂ systems require particular attention?
| Because CO₂ needs no lubrication, so oil separators are unnecessary |
| Because CO₂ is flammable and separators must not be used |
| Because sight glasses and level indicators must not be used in CO₂ systems |
| Because of very high pressures – adequate PS and protection devices are required |
43
Difficult
What is the critical pressure of CO₂ (R744)?
| Approx. 120 bar |
| Approx. 74 bar (abs) |
| Approx. 31 bar |
| Approx. 10 bar |
44
Difficult
What characterises the transcritical process in CO₂ systems?
| It is irrelevant to system operation |
| Heat rejection takes place above the critical point – the refrigerant does not condense in the conventional way (gas cooler instead of condenser) |
| Conventional condensation occurs |
| It occurs only at low temperatures |
45
Difficult
What characterises the subcritical CO₂ process?
| The absence of evaporation |
| Operation above the critical point |
| The absence of condensation |
| The conventional condensation process below the critical point |
46
Difficult
When can dry ice (solid CO₂) form?
| At high pressure |
| At high temperature |
| During normal operation of the system |
| When the pressure drops suddenly below the triple point (approx. 5.2 bar abs, −56.6 °C), e.g. when venting liquid CO₂ or charging liquid into an evacuated system |
47
Difficult
What risks are associated with dry ice forming in a CO₂ system?
| No risk |
| Blocked pipes and valves and system damage (and a sharp pressure rise when it thaws) |
| Improved efficiency |
| Pressure reduction |
48
Difficult
How does CO₂ saturation pressure change as temperature increases?
| It remains the same |
| It first decreases, then increases |
| It increases rapidly |
| It decreases |
49
Difficult
What happens to CO₂ above the critical point?
| It turns into a solid |
| It ceases to conduct heat |
| It turns into a liquid |
| It transitions to a supercritical state (no distinction between liquid and gas) |
50
Difficult
What is the main difference between a dry-expansion and a flooded evaporator?
| A dry-expansion evaporator is filled with liquid, a flooded one with vapour |
| A dry-expansion evaporator needs no expansion valve, a flooded one does |
| A dry-expansion evaporator always has a lower pressure than a flooded one |
| In a dry-expansion evaporator the refrigerant completely evaporates and is superheated in the evaporator; in a flooded one part of the refrigerant remains liquid (incomplete evaporation, no superheat) |
51
Difficult
What is the typical pressure in the evaporator of an R717 deep-freeze system (below −40 °C)?
| Positive pressure of 5–10 bar |
| Atmospheric pressure, approx. 1 bar abs |
| Positive pressure of 10–20 bar |
| Below atmospheric (approx. 0.7 bar abs at −40 °C) |
52
Difficult
Why are PFAS formed by the decomposition of certain F-gases (e.g. TFA from HFOs) problematic?
| They are readily biodegradable |
| They are very persistent, accumulate in the environment (e.g. water) and may be toxic |
| They are climate- and environment-neutral |
| They cause rapid cooling of the atmosphere |
53
Difficult
How is oil managed in R717 systems?
| Oil collecting at the lowest points of vessels is regularly checked and drained, because it impairs heat transfer |
| Oil has no effect on system operation |
| Oil requires no monitoring |
| Oil can be mixed with any refrigerant |
54
Difficult
What should be done with contaminated R717?
| Dilute it with water and reuse it |
| Release it into the atmosphere |
| Purify it or send it for disposal in accordance with regulations |
| Continue to use it without restriction |
55
Difficult
What should be done if an NH₃ leak is detected?
| Carry on working wearing a dust mask |
| Carry on working with the room door open |
| Evacuate people immediately and raise the alarm; stop the leak only if it is safe to do so and with suitable PPE (respiratory protection) |
| Increase the pressure in the system |
56
Difficult
What role do scrubbers play in NH₃ systems?
| They store the refrigerant |
| Neutralise ammonia through absorption in a liquid (e.g. water) |
| They increase the pressure in the system |
| They are used to measure temperature |
57
Difficult
How should the system be prepared before filling with R717?
| The pressure must be increased above the standard level |
| Check for leaks, remove air and moisture, and create a vacuum |
| Simply start it up |
| There is no need to check it |
58
Difficult
What are the transport requirements for R717?
| It can be carried in open containers |
| Transport is not regulated |
| It can be carried without labelling |
| It must be carried in suitable, labelled packagings in accordance with ADR (UN 1005, class 2, code 2TC) |
59
Difficult
What is the main characteristic of R744 (CO₂) refrigeration systems?
| Low energy efficiency under all conditions |
| No need for control |
| Low operating pressures |
| Very high operating pressures |
60
Difficult
What are the requirements for piping materials in CO₂ systems?
| Only plastics |
| They must withstand high pressures (e.g. stainless steel, high-strength copper-alloy tubes such as K65) |
| Any material may be used |
| It doesn't matter |
61
Difficult
How does a booster system work in CO₂ installations?
| It reduces the refrigerant quantity |
| It is used to store refrigerant |
| Low-temperature (LT) compressors discharge into the suction of medium-temperature (MT) compressors – two-stage compression in a single circuit |
| It reduces evaporator pressure |
62
Difficult
Why is pressure optimisation in CO₂ systems crucial?
| It reduces the amount of refrigerant |
| It doesn’t matter |
| It enables the system to achieve maximum energy efficiency in transcritical mode |
| It reduces the ambient temperature |
63
Difficult
What role does parallel compression play in CO₂ systems?
| It compresses flash gas from the intermediate receiver directly to high pressure, improving efficiency |
| It lowers the ambient temperature |
| It has no significance |
| It increases energy consumption |
64
Difficult
How does an ejector work in a CO₂ system?
| It lowers the evaporator temperature |
| It uses the energy of the higher-pressure refrigerant to raise the pressure of the refrigerant from the lower stage, which improves efficiency |
| Stores the refrigerant |
| It increases the amount of refrigerant |
65
Difficult
What is the function of liquid ejectors in CO₂ systems?
| They reduce atmospheric pressure |
| They return liquid from the separator and allow partially flooded evaporator operation (better evaporator feed) |
| They raise the refrigerant temperature |
| They increase the amount of oil |
66
Difficult
What are the characteristics of partially flooded systems in CO₂ systems?
| Low operating pressure |
| Lack of regulation |
| The presence of liquid in the evaporator, which improves heat transfer and efficiency |
| The absence of liquid in the evaporator |
67
Difficult
What is the main risk associated with standstill pressure in CO₂ systems?
| Increased efficiency |
| A pressure rise as the refrigerant warms up during standstill (possibly exceeding PS and lifting the relief valves) |
| A drop in temperature |
| A decrease in refrigerant quantity |
68
Difficult
How is standstill pressure limited in CO₂ systems?
| By raising the plant-room temperature |
| By using an auxiliary standstill (stagnation) cooling unit, e.g. cooling the receiver, with back-up power, and by selecting an adequate PS and relief valves |
| By completely shutting down the system and power supply |
| By increasing the refrigerant charge |
69
Difficult
What does standstill (stagnation) of a CO₂ system mean, and why is it important?
| Normal system operation |
| A state with no compressor operation or refrigerant flow – pressure rises with ambient temperature and may exceed PS |
| Improved efficiency |
| A drop in system temperature |
70
Difficult
What must the label of a flammable refrigerant cylinder include?
| Only the refrigerant name |
| Information about the cylinder owner |
| Only the net weight |
| The refrigerant name, the UN number, the hazard label (e.g. 2.1 – flammable gas) and basic safety information |
71
Difficult
Why is the absence of a 'flammable refrigerant' label on equipment a serious hazard?
| It reduces system efficiency |
| It may lead to the use of tools that are ignition sources |
| It may lead to the wrong oil being selected |
| It has no significant effect on safety |
72
Difficult
Which set of information on the label of a flammable refrigerant cylinder is crucial from a safety perspective?
| Gross weight and batch number |
| Cylinder colour and date of manufacture |
| Name of the substance, hazard label (ADR) / GHS pictogram (CLP), UN number |
| Manufacturer’s name and country of origin |
73
Difficult
What is the purpose of gas detectors in a room with a refrigeration system?
| Monitoring pipe pressure |
| Controlling compressor capacity |
| Early leak detection and triggering of measures preventing health risks and explosive atmospheres (alarm, ventilation, shut-off) |
| Measuring refrigerant temperature |
74
Difficult
How often should gas detection sensors in a machinery room be checked?
| Once every 5 years |
| Before every start-up of the unit |
| Only after a leak has occurred |
| According to the manufacturer's instructions and regulations – at least every 12 months |
75
Difficult
Where should a gas detector be located according to EN 378?
| Near the control panel |
| Where the refrigerant would accumulate: low (near the floor) for refrigerants heavier than air, high (near the ceiling) for lighter ones such as NH₃ |
| Only at the room entrance |
| Anywhere in the room |
76
Difficult
What safety checks should be carried out when installing a new refrigeration system with a flammable refrigerant?
| Only the compressor power |
| Only that the air filter is new |
| The colour of pipes and hoses |
| The presence of health and safety signage, adequate ventilation and gas detectors |
77
Difficult
What are the requirements for emergency exits from a refrigeration machinery room?
| At least two exits are required and signage is optional |
| Outward-opening doors and signed escape routes (number of exits per the standard) |
| In small machinery rooms emergency exits need not be signed |
| One exit with a sign stating the refrigerant type is sufficient |
78
Difficult
Which installation measure for a flammable-refrigerant system improves its energy efficiency?
| A thorough tightness test and evacuation (dehydration) of the system |
| Charging above the nameplate quantity |
| Restricting room ventilation |
| Omitting the filter-drier |
79
Difficult
Why is it important to limit the refrigerant charge in HC systems?
| It limits the possibility of reaching a flammable concentration (≥ LFL) in a leak, increasing safety |
| It increases capacity |
| It doesn't matter |
| It lowers the temperature |
80
Difficult
Which safety class applies to R744?
| A2. |
| A1 |
| B2L |
| A3 |
81
Difficult
In a simple single-stage R744 system without an intermediate receiver (refrigerant flows from the gas cooler directly to the expansion valve), operating transcritically at 90 bar with a gas-cooler outlet temperature of 35 °C, the refrigerant upstream of the expansion valve is…
| …a subcooled liquid |
| …saturated vapour at intermediate pressure |
| …a two-phase mixture at intermediate pressure |
| …a supercritical fluid |
82
Difficult
In R744 transcritical systems, the gas cooler outlet valve controls:
| The inlet temperature to the gas cooler |
| The outlet temperature of the gas cooler |
| The gas cooler fans |
| The pressure in the gas cooler |
83
Difficult
Which statement best describes the behaviour of R717 and mineral compressor oil?
| R717 does not mix with the oil; the oil, being heavier than liquid NH₃, collects beneath it at the lowest points (mainly on the low-pressure side) |
| An oil return line cannot be used in R717 systems because the oil is too hot |
| R717 does not mix with the oil; the oil collects on the high-pressure side above the R717 |
| R717 mixes very well with the oil, which easily returns to the compressor |
84
Difficult
What is the main reason for using K65 copper tubing in some R744 systems?
| They can withstand higher pressures |
| They have good low-temperature performance |
| They come in a wider range of diameters |
| They bend easily |
85
Difficult
Which statement about installing Schrader valves is correct?
| Schrader valves must not be used in R744 systems |
| When brazing the valve body, the core must be removed, then refitted and tightened to the correct torque |
| Hydrocarbons leak through Schrader valves |
| All Schrader cores are suitable for all refrigerants |
86
Difficult
Which refrigerant can be detected with phenolphthalein paper?
| R717 |
| R1270 |
| R1234ze(E) |
| R744 |
87
Difficult
How does an undercharge affect the high-pressure side (without discharge pressure control)?
| Discharge (condensing) pressure and subcooling will both be lower |
| Discharge pressure higher, subcooling lower |
| Discharge pressure lower, subcooling higher |
| Discharge pressure higher, subcooling higher |
88
Difficult
What is the benefit of adding helium as a tracer gas to nitrogen in a pressure test?
| It has a distinctive odour that helps locate the leak |
| Its small atoms pass easily through leaks and are detected |
| It reacts with refrigerant residues, producing a visible colour change |
| It has a higher pressure than pure nitrogen in the same cylinder |
89
Difficult
Why should an evacuated R744 system initially be charged with refrigerant in the vapour phase?
| To avoid damaging the compressor with liquid CO₂ |
| To charge R744 more slowly and measure it more accurately |
| To prevent dry ice forming (until approx. 5.2 bar abs is exceeded) |
| To prevent the drain valve on the receiver from opening |
90
Difficult
If moisture remains in an R744 system because it was not properly evacuated (dehydrated), what is the likely consequence?
| Reduced cooling capacity |
| Formation of carbonic acid, which damages the system |
| Excessive discharge pressure |
| Formation of hydrogen fluoride and hydrofluoric acid |
91
Difficult
Which system may require manual oil recovery?
| R744 cascade system |
| Secondary system using R744 |
| An R717 system |
| Supercritical ‘booster’ system using R744 |
92
Difficult
The pressure of R744 at a saturation temperature of 20 °C is approx.
| 56 bar g |
| 25 bar g |
| 14 bar g |
| 90 bar g |
93
Difficult
Which refrigerant is lighter than air?
| R717 |
| R1270 |
| R744 |
| R1234ze(E) |
94
Difficult
What hazards are associated with a safety group A3 refrigerant?
| Higher toxicity, no flame propagation |
| Lower toxicity, no flame propagation |
| Higher flammability, lower toxicity |
| Lower flammability, lower toxicity |
95
Difficult
What is the GWP of R32 (per AR4, as used in Regulation (EU) 2024/573)?
| 3922 |
| 6 |
| 0 |
| 675 |
96
Difficult
What factors are taken into account when determining the maximum charge for comfort air-conditioning/heating applications?
| Lower flammability limit, height of the indoor unit, floor area |
| Practical limit, height of the indoor unit, floor area |
| Lower flammability limit, room volume |
| Practical limit, room volume |
97
Difficult
What compressor displacement is required for R1270 compared with an R404A compressor in the medium-temperature range (cold room)?
| About half |
| Similar |
| About 1.5 times larger |
| About 6 times larger |
98
Difficult
At an ambient temperature of 25 °C, the standstill pressure in the low-pressure stage of an R744 cascade (without standstill cooling) will typically be…
| …the same as the relief valve set pressure |
| …the same as the high-pressure switch setting |
| …approx. 27.5 bar g |
| …higher than the maximum allowable pressure (PS) of the low-pressure stage |
99
Difficult
What is the correct definition of critical temperature?
| The temperature at which a substance changes from a gaseous to a solid state |
| The temperature above which there are no distinct liquid and gaseous phases |
| The temperature at which, for certain substances, electrical resistance is zero |
| The temperature at which the vapour pressure of a liquid is equal to the ambient pressure surrounding the liquid |
100
Difficult
In the gas cooler of a transcritical system, the supercritical working fluid…
| …rejects heat during a phase change |
| …rejects heat at constant temperature and pressure |
| …rejects heat as its temperature falls |
| …rejects heat as its pressure falls |
101
Difficult
R717 is highly corrosive to:
| copper (and its alloys) |
| titanium |
| aluminium |
| stainless steel |
102
Difficult
What can be the effect of a relief valve lifting repeatedly?
| The valve stays fully open permanently |
| The set pressure increases |
| The valve may not reseat tightly and its set (opening) pressure may decrease |
| The valve no longer opens |
103
Difficult
What is the relationship between the pressure (p) and temperature (T) of nitrogen at the start (1) and end (2) of a tightness test (p absolute, T in kelvin)?
| p₂ = T₂/(p₁ × T₁) |
| p₂ = (p₁ × T₁)/T₂ |
| p₂ = T₁/(p₁ × T₂) |
| p₂ = (p₁ × T₂)/T₁ |
104
Difficult
What is the recommended pre-alarm level for fixed leak detection systems for R717?
| 500,000 ppm |
| 50,000 ppm |
| 500 ppm |
| 5,000 ppm |
105
Difficult
Why are compressors with a separate motor (open type) mostly used in R717 systems?
| To increase the refrigerant charge |
| Because NH₃ attacks copper motor windings, so hermetic compressors with conventional windings are not used |
| To lower the condensing pressure |
| Because they are cheaper |
106
Difficult
Which type of compressor is most commonly used in large ammonia systems?
| A reciprocating or screw compressor |
| Hermetic scroll |
| Rotary vane compressor |
| Diaphragm compressor |
107
Difficult
How is the capacity of a piston compressor regulated in NH₃ systems?
| By increasing the condensing pressure |
| By reducing the refrigerant charge |
| Solely by adjusting the oil volume |
| By unloading the cylinders or changing the rotational speed |
108
Difficult
How is the capacity of a screw compressor most commonly controlled?
| By adjusting the oil level |
| By using a slide valve |
| By changing the type of oil |
| By closing the suction valve |
109
Difficult
When is two-stage compression used in NH₃ systems?
| Only in small systems |
| At low evaporating temperatures (pressures) and high pressure ratios |
| At small temperature differences |
| Only with water-cooled condensers |
110
Difficult
What is the advantage of two-stage compression over single-stage compression?
| Higher energy consumption |
| Lower efficiency |
| No need for a separator |
| Higher efficiency and lower discharge temperature |
111
Difficult
How does an evaporative condenser used in NH₃ systems work?
| Operates without a fan |
| It utilises the evaporation of water to increase cooling efficiency |
| It transfers heat only to the air |
| It does not require a water supply |
112
Difficult
What is the function of the liquid separator in an NH₃ system?
| It prevents liquid from entering the compressor |
| Increases the discharge temperature |
| Regulates the condensing pressure |
| It separates oil from the refrigerant |
113
Difficult
What is the purpose of monitoring the liquid level in the separator?
| To control the condenser fan |
| To increase the oil volume |
| To reduce the condensing temperature |
| To maintain the correct refrigerant level and prevent the compressor from flooding |
114
Difficult
What is the role of the float switch in NH₃ systems?
| It monitors the liquid level in the tank or separator |
| It controls the fan’s operation |
| It regulates the condensation temperature |
| It is used to detect leaks |
115
Difficult
What is a thermosyphon in NH₃ systems?
| An oil circulation pump |
| A defrosting device |
| A system with gravity-driven (natural) circulation of liquid refrigerant caused by density differences, used e.g. for screw compressor oil cooling |
| A type of safety valve |
116
Difficult
Why are oils that are immiscible with the refrigerant used in NH₃ systems?
| Because the oil mixes only with water |
| To reduce the pressure |
| Because NH₃ does not mix with most compressor oils |
| To increase the amount of refrigerant |
117
Difficult
What is the main function of an oil separator in NH₃ systems?
| To lower the condensation temperature |
| To increase fan efficiency |
| Removing moisture from the system |
| To separate the oil from the refrigerant and return the oil to the compressor |
118
Difficult
In which NH₃ system does the refrigerant evaporate completely with superheat in the evaporator, fed by an expansion valve?
| A pumped liquid-recirculation system |
| A direct-expansion (DX) system |
| A glycol system |
| An indirect system |
119
Difficult
What is the characteristic feature of a flooded evaporator system?
| The evaporator contains a large amount of liquid, which improves heat transfer |
| No separator is used |
| The evaporator is filled exclusively with vapour |
| No level control is required |
120
Difficult
What is the main difference between a direct and an indirect system?
| In an indirect system, NH₃ flows directly into the space being cooled |
| In an indirect system, no compressor is used |
| In an indirect system, NH₃ cools an intermediate medium (e.g. glycol), which in turn cools the load |
| In a direct system, there is no evaporator |
121
Difficult
Which parts of a refrigeration system should be given particular attention during a leak check?
| Only compressor connections, because they are the only parts subject to vibration |
| Only condenser connections, because the refrigerant is liquid there |
| Compressor and receiver connections, because the pressure is highest there |
| Joints, valves incl. stems, seals, parts subject to vibration, connections to safety devices |
122
Difficult
Leak checks can be carried out using various methods. Which pair is correct?
| Physical and chemical methods |
| Material quality control methods and electronic methods |
| Direct and indirect methods |
| Methods with and without quality control of supplies |
123
Difficult
To whom can leak checks of stationary refrigeration equipment containing F-gases be entrusted?
| Any leak-testing specialist |
| A natural person holding a certificate covering leak checks (A1, A2 within its charge limit, or E) |
| An employee appointed by the owner of the installation |
| A person who has carried out such checks before |
124
Difficult
What conditions must be met to use UV dye for leak checking?
| It is sufficient that introducing dye into the circuit is technically feasible |
| A UDT authorisation for pressure testing is required |
| It is sufficient to have a UV lamp, dye and safety goggles |
| Manufacturer approval of the method and a certificate covering breaking into the circuit |
125
Difficult
Which leak-checking methods are considered direct methods?
| Vacuum test and foam solution |
| Pressure-change measurement and immersion in water |
| 1. gas detection devices (portable or fixed leak detection system), 2. UV detection fluid or dye, 3. bubble/foam solutions |
| Nitrogen with tracer gas and pressure measurement |
126
Difficult
What do indirect leak-checking methods involve?
| Leak detection with UV dye |
| Ultrasonic measurement |
| Leak detection with an electronic detector |
| A visual and manual check and analysis of parameters: pressure, temperature, compressor current, liquid levels and recharge volume |
127
Difficult
What does a vacuum (decay) test involve?
| The pump is restarted every time the system pressure rises |
| After isolating the pump, you check whether the system pressure rises |
| The pump runs continuously to hold the required vacuum for the test |
| With the pump running, you watch the vacuum gauge reading |
128
Difficult
How often should leak tests be carried out on equipment containing 1.5 kg of R404A refrigerant (5.9 tonnes of CO₂ equivalent)?
| Only when servicing the unit. |
| On initial commissioning. |
| At least once every 12 months. |
| Once every six months. |
129
Difficult
How often should leak tests be carried out on equipment containing 7 kg of R404A refrigerant (27.45 tonnes of CO₂ equivalent)?
| At least once every 12 months. |
| Once every six months. |
| Only when servicing the unit. |
| On initial commissioning. |
130
Difficult
Under Regulation (EU) 2024/573, a leakage detection system is mandatory when:
| the F-gas charge of the refrigeration equipment is 500 t CO₂ eq or more |
| the equipment operates in an enclosed space |
| the charge is 100 kg or more of ozone-depleting substances |
| the equipment contains a flammable refrigerant in any quantity |
131
Difficult
Which leak-checking method may NOT be used by a holder of a Category E certificate?
| Visual inspection |
| Leak checking with a fluorescent dye introduced into the circuit |
| Measurement with a handheld electronic detector |
| Checking with a foaming solution |
132
Difficult
Within what timeframe must a leak test be carried out on a stationary refrigeration system after a leak has been repaired, in accordance with EU Regulation 2024/573 on F-gases?
| At any time. |
| Between 24 hours and 1 month after the repair. |
| Immediately after the repair. |
| At the next periodic inspection. |
133
Difficult
How often must refrigeration equipment containing ≥500 t CO₂ eq of F-gases be checked if (contrary to Article 6) no leakage detection system is installed?
| Every month |
| Every 6 months |
| Every 12 months |
| Every 3 months |
134
Difficult
What is the basis of the GWP values in Regulation (EU) 2024/573?
| For HFCs (Annex I) – mainly the IPCC Fourth Assessment Report (AR4); for HFOs and non-fluorinated substances (Annexes II and VI) – the Sixth Assessment Report (AR6) |
| AR6 for all substances |
| AR4 for all substances |
| Each Member State sets its own GWP values |
135
Difficult
An air conditioner (not hermetically sealed) contains 2.5 kg of R410A (GWP 2088). How often must it be checked for leaks?
| At least every 12 months (5.22 t CO₂ eq) |
| Every 6 months |
| Every 3 months |
| No checks required (below 3 kg) |
136
Difficult
When is labelled hermetically sealed equipment containing HFCs (Annex I) exempt from leak checks?
| When it contains less than 5 t CO₂ eq |
| When it contains less than 10 t CO₂ eq, and in residential buildings also when it contains less than 3 kg of F-gases |
| Never – hermetically sealed equipment is always checked |
| Always, regardless of charge |
137
Difficult
Is a chiller containing 50 kg of R1234ze(E) subject to leak checks under Regulation (EU) 2024/573?
| No – the threshold is 5 t CO₂ eq and 50 kg of R1234ze is below 1 t CO₂ eq |
| No – HFOs are not subject to leak checks |
| Yes – every 12 months, because its GWP is low |
| Yes – at least every 6 months (every 12 months with a leakage detection system) |
138
Difficult
In 2026, may an existing refrigeration installation using R404A (GWP 3922) be topped up with virgin refrigerant?
| No – only reclaimed or recycled R404A is allowed (until 1 January 2030) |
| Yes – the ban applies only to equipment ≥40 t CO₂ eq |
| Yes – bans apply only to new equipment |
| Yes, if the equipment has a leakage detection system |
139
Difficult
After 1 January 2026, may an R410A (GWP 2088) air conditioner be serviced using virgin R410A?
| Yes – the servicing ban for air conditioners and heat pumps covers F-gases with GWP ≥ 2500 |
| No – the ban covers all refrigerants with GWP ≥ 750 |
| Only with reclaimed refrigerant |
| No – the ban covers all HFCs |
140
Difficult
Since 1 January 2025, may a new single-split air conditioner containing 1.5 kg of R410A be placed on the market?
| Yes, if the unit is hermetically sealed |
| Yes – the ban applies only to units >12 kW |
| No – single splits <3 kg with F-gases of GWP ≥ 750 are banned |
| Yes – the ban applies from 2029 |
141
Difficult
From when is it prohibited to place on the market split air-to-air systems up to 12 kW containing F-gases with GWP ≥150 (unless required for safety)?
| From 1 January 2025 |
| From 1 January 2035 |
| From 1 January 2029 |
| From 1 January 2027 |
142
Difficult
Which persistent atmospheric degradation product of R1234yf is classed as a PFAS?
| Carbon dioxide |
| Carbonic acid |
| Trifluoroacetic acid (TFA) |
| Ozone |
143
Difficult
What is the maximum R290 charge per circuit of a commercial refrigerating appliance (e.g. a cabinet) according to EN IEC 60335-2-89:2022?
| 150 g |
| 1.5 kg |
| 1.2 kg |
| 13 × LFL ≈ 494 g |
144
Difficult
Calculate the maximum R32 charge (LFL = 0.307 kg/m³) for a wall-mounted air conditioner (h₀ = 1.8 m) in a 20 m² room using m_max = 2.5 × LFL^1.25 × h₀ × A^0.5.
| approx. 13.8 kg |
| approx. 0.46 kg |
| approx. 1.5 kg |
| approx. 4.6 kg |
145
Difficult
What is the maximum quantity of R290 (class 2, group F) that may be carried per transport unit under the ADR 1.1.3.6 exemption?
| 1000 kg |
| Unlimited |
| 20 kg |
| 333 kg |
146
Difficult
What is the charge limit m₃ = 130 m³ × LFL for R290 (LFL = 0.038 kg/m³) according to IEC 60335-2-40?
| approx. 0.15 kg |
| approx. 13 kg |
| approx. 4.94 kg |
| approx. 0.99 kg |
147
Difficult
Why does the efficiency of transcritical CO₂ systems fall in warm climates, and how is this mitigated?
| Efficiency does not depend on climate |
| CO₂ freezes in the gas cooler – heaters are used |
| At high ambient temperatures the system operates transcritically with large throttling losses – parallel compression and ejectors are used, among others |
| Gas cooler pressure drops – extra charge is added |