What is determined by checking the hydraulic nameplate located on the sprinkler riser?

The hydraulic nameplate, typically found on the sprinkler riser, provides essential information regarding the sprinkler system's design and requirements. It indicates the original hazard classification, which reflects the intended use of the building and the level of fire protection required. This classification is vital for understanding how the sprinkler system was designed to operate effectively under specific conditions to mitigate fire hazards.

The other choices, while related to fire safety, do not accurately describe what is determined by the hydraulic nameplate. The current fire risk is assessed through various factors, including occupancy and fire load, but is not found on the nameplate. Water supply capacity may be included in the system’s overall design but isn't the primary focus of the hydraulic nameplate. Lastly, the system maintenance schedule is determined by different factors, including inspections and testing records, rather than the hydraulic nameplate itself.