According to NFPA 20, Standard for the Installation of Stationary Pumps for Fire Protection, a centrifugal fire pump must meet three critical performance points on its characteristic curve. One of these points is the overload condition. At 150 percent of its rated capacity (flow), the pump must be capable of providing not less than 65 percent of its total rated head (pressure). This requirement ensures that the pump can still deliver adequate pressure to the system even when flowing a significantly higher volume of water than its nominal rating, which is crucial during a large fire event.

A. 50%: This pressure is below the minimum performance threshold required by NFPA 20 for the 150% flow condition.

C. 100%: This is the minimum pressure required at 100% of the rated flow, not at the 150% overload condition.

D. 120%: This value is typically associated with the maximum allowable pressure at churn (zero flow), not a minimum at 150% flow.

1. NFPA 20, Standard for the Installation of Stationary Pumps for Fire Protection, 2022 Edition.

Section 4.10.2.1: "A centrifugal fire pump for fire protection shall be selected to furnish not less than 150 percent of rated capacity at not less than 65 percent of total rated head."

2. Isman, K. E. (2017). Fire Protection Hydraulics and Water Supply Analysis (3rd ed.). Fire Protection Publications, Oklahoma State University.

Chapter 10, Fire Pumps, Page 318: "The NFPA 20 standard requires that all fire pumps have a characteristic curve with three specific points. ... The third point is at 150 percent of the rated flow. At this point, the pump must be able to produce at least 65 percent of the rated pressure."

3. SFPE Handbook of Fire Protection Engineering (5th ed.). (2016). Springer.

Chapter 21, Water-Based Fire Protection System Design, Section 21.5.2.1, Pump Characteristics: "NFPA 20 requires that the pump characteristic curve have a shape such that at 150 % of rated flow, the head is at least 65 % of rated head." (DOI: https://doi.org/10.1007/978-1-4939-2562-421)