ATP Refrigeration Systems & Components 5

Question 1

According to ASHRAE 15, a refrigerating system machinery room must be equipped with a refrigerant detector that activates at a concentration not exceeding:

Accepted Answer

The ASHRAE Standard 34 occupational exposure limit (OEL) for the refrigerant in use

Answer

ASHRAE 15 requires refrigerant detectors in machinery rooms to alarm and activate ventilation at concentrations not exceeding the refrigerant's occupational exposure limit (OEL) as defined by ASHRAE 34.

Question 2

A high-pressure relief valve on a refrigeration system is set to relieve at a pressure that:

Accepted Answer

Does not exceed the maximum allowable working pressure (MAWP) of the high-side components

Answer

Pressure relief valves must be rated and set to relieve at or below the MAWP of the weakest component on the high-pressure side to prevent equipment failure and ensure personnel safety.

Question 3

What is the primary function of an electronic expansion valve (EEV) compared to a traditional thermostatic expansion valve?

Accepted Answer

The EEV provides faster, more precise superheat control using a stepper motor and electronic controller

Answer

EEVs use a stepper or pulse-width modulated motor controlled by an electronic controller reading multiple inputs, enabling faster and more accurate superheat modulation than a mechanical TXV, improving efficiency especially at part-load conditions.

Question 4

When using a pressure-enthalpy (P-H) diagram to analyze a refrigeration cycle, the refrigeration effect is represented by:

Accepted Answer

The horizontal distance (enthalpy difference) across the evaporator on the low-pressure line

Answer

On a P-H diagram, the refrigeration effect equals the enthalpy of the refrigerant leaving the evaporator minus the enthalpy entering the expansion device, read as a horizontal span at low-side pressure.

Question 5

In a hot-gas defrost system, refrigerant used for defrosting is drawn from:

Accepted Answer

The high-pressure discharge side of the compressor and directed to the frozen evaporator coil

Answer

Hot-gas defrost diverts high-temperature, high-pressure discharge gas directly from the compressor to the evaporator, where it condenses and releases latent heat to melt frost from the coil.

(ATP) Accredited Tier Professional Certification (Cooling & Refrigeration) Practice Test

(ATP) Accredited Tier Professional Certification (Cooling & Refrigeration) Practice Test

ATP Refrigeration Systems & Components 5