Under abnormal conditions, what is the coil suction header pressure for a low temperature room using ammonia (NH3)?

The correct answer reflects the coil suction header pressure for a low-temperature refrigeration system using ammonia (NH3) under abnormal conditions. Ammonia has specific thermodynamic properties that define its behavior in refrigeration systems. At lower temperatures typical for low-temperature applications (like freezer rooms), the saturation pressure of ammonia corresponds to the temperature at which it evaporates to absorb heat effectively.

For the normal operation of low-temperature refrigeration using ammonia, a suction header pressure that correlates to -42°F is within the expected operating range. This temperature indicates the level of cooling needed to keep a low-temperature room, such as a freezer, below freezing and allows for efficient heat absorption from the environment.

When considering other temperature options, they either fall under the range typical for medium temperature systems or are not suitable for low-temperature applications, where effective refrigeration and heat transfer need to be achieved. Hence, identifying -42°F as the correct coil suction header pressure ensures that the system will adequately support the intended functional requirements of a low-temperature ammonia refrigeration system.