Final answer:
The licensure required for a shift engineer in a 500 bhp hot water plant is usually an advanced level such as a 1st class grade A or B license, though this can vary by region.
Step-by-step explanation:
The subject of your question is related to the professional licensure required for a shift engineer working in a high pressure, high temperature, hot water plant of 500 bhp. The licensing requirements for such a position will depend on regional or national regulations which specify the type of certification needed to operate as an engineer within a power plant.
In general, engineering licenses are categorized into different classes and grades based on the level of responsibility, the complexity of the systems managed, and the degree of risk involved. For a high-pressure, high-temperature environment such as the one described, an engineer would typically be required to have an advanced level of certification due to the potential hazards and technical challenges associated with operating such a plant.
If we were to consider usual licensing protocols, one might expect this role to require at least a 1st class grade A or B license due to the significant amount of boiler horsepower (bhp) involved. Nevertheless, without specific details regarding the jurisdiction and local requirements, it is difficult to provide a definite answer.