LOAD CALCULATION AND SIZING OF FIRE PUMP & JOCKEY PUMP

Summary

In this technical discussion, the speaker outlines the electrical design of a system featuring a transformer, generator set, and various pumps. Key elements include a utility feeding a transformer, a controller for a jacket pump, and detailed calculations for wire sizes and amperages based on specific electrical codes. The analysis emphasizes safety and efficiency, highlighting the importance of proper sizing for both the main service feeder and backup generator. The session aims to enhance understanding among engineers and electricians, fostering a collaborative spirit in ensuring the system operates effectively.

Takeaways

• 🔌 The system includes a utility transformer that supplies power to the building's normal loads and a disconnect switch.
• ⚡ The diagram involves a generator set that feeds an MCCB through an Automatic Transfer Switch (ATS).
• 💧 The system features a 50 HP pump and a fire pump connected to the generator through the ATS.
• 📊 Calculations for wire sizes are based on load capacities and standards, ensuring safe and efficient operation.
• 🧮 A 125% safety factor is applied in calculations for the pumps to determine appropriate wire sizes.
• 📏 The calculations use specific tables and formulas to ensure compliance with electrical codes.
• 🔍 The rated current and wire size for the main feeder and controller are calculated to manage load effectively.
• 🔥 The system includes fire-rated conductors for safety and compliance with fire protection standards.
• 📈 Overcurrent protection device (OCPD) sizing is crucial, with specific amperage values calculated for safe operation.
• 🔧 Emphasis is placed on sharing knowledge and best practices among engineers and electricians for system safety.

Q & A

What is the main purpose of the utility discussed in the transcript?

The utility feeds a transformer that powers the first disconnect switch and normal loads of the building.

What is the significance of the ATS mentioned in the discussion?

The ATS (Automatic Transfer Switch) is crucial for switching between the normal power supply and the generator supply for the pump system.

What is the capacity of the generator set discussed?

The generator set is used to power various loads and is mentioned in conjunction with a fire pump.

How is the wire size for the pump calculated?

The wire size is calculated using the formula of 125 percent of the full load current (FLC) and is referenced against standards such as NEC Table 310.16.

What does the term 'ocpd' stand for in the context of the discussion?

'ocpd' stands for Overcurrent Protection Device, which is necessary to protect the system from overload conditions.

Why is the calculation for the jacket pump similar to that of the main pump?

Both pumps require similar calculations for wire sizing and load handling due to their operational characteristics.

What is the minimum rated capacity for the wire specified in the calculations?

The minimum rated capacity specified in the calculations is 81 amperes.

How is the fire pump's overload calculation approached in the discussion?

The fire pump's overload calculation considers the locked rotor current (LRC) and uses a specific formula to determine the appropriate overprotection device rating.

What are the voltage and frequency specifications mentioned for the pumps?

The pumps are specified to operate at three-phase 440 volts and 60 hertz.

What is the outcome of the calculations presented for the main service feeder?

The calculations for the main service feeder resulted in determining wire sizes and overcurrent protection ratings to ensure safe and efficient operation.