NFPA 20 includes guidelines for the selection and installation of jockey pumps, but it doesn't provide a specific size in terms of horsepower or flow rate for jockey pumps. Instead, it emphasizes the importance of maintaining a stable pressure within the fire protection system. The jockey pump's size should be determined based on factors such as the system's maximum allowable pressure drop, the leakage rate of the system, and the anticipated changes in pressure over time.
To accurately determine the appropriate size for a jockey pump in accordance with NFPA standards, it's recommended to work with a professional fire protection engineer or consultant. These experts can perform hydraulic calculations and take into consideration the specific characteristics of your fire protection system to ensure that the jockey pump is appropriately sized to maintain system pressure within the desired range.
Keep in mind that codes and standards may be updated over time, so I recommend checking the latest version of NFPA 20 or consulting with a current expert in fire protection engineering to get the most up-to-date and accurate information regarding jockey pump sizing.