Final answer:
In refrigeration system safety, 'C' stands for the minimum required rate discharge capacity of a pressure-relief device, measured in btu/minute.
Step-by-step explanation:
In the context of refrigeration systems, the term "C" in the formula C = Fd1 refers to the minimum required rate discharge capacity of the pressure-relief device or fusible plug for a refrigerant-containing vessel. The correct unit for "C" is btu/minute (British thermal units per minute), which is a measure of the rate of energy discharge. This parameter is crucial for the design and safety of refrigeration systems, ensuring that pressure within the containers can be relieved at an appropriate rate to prevent damage or accidents caused by overpressure. Therefore, the answer to the question, 'What is "C" equal to?' is A) btu/minute.