Fire pump protection

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anbm

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TX
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Designer
Fire pump controller/ats:
  • Normal power circuit comes from a tap to poco transformer's secondary side without protection.
  • Generator power circuit comes from a main emergency distribution panel (1st panel downstream of standby generator) and this circuit is protected by a breaker in panel.
Question:
  • On normal power side (utility power), no breaker is needed, but per NEC, if a breaker is installed between xfmr and fire pump, the breaker needs to be sized to handle motor inrush current, i.e., CB size = 6 x fire pump motor's FLA.
  • For generator power circuit, per NEC, the breaker to serve circuit to fire pump is not required to size to carry motor inrush current but = 2.5 X motor's FLA (article 430 for thermal magnetic breaker).
Question: when fire pump is on generator power, fire pump's inrush current never occur???
 
The generator will not likely be able to start the fire pump without a large voltage sag that serves to act as a soft start and reduce the inrush.
 
anbm said:
Fire pump controller/ats:
  • Normal power circuit comes from a tap to poco transformer's secondary side without protection.
  • Generator power circuit comes from a main emergency distribution panel (1st panel downstream of standby generator) and this circuit is protected by a breaker in panel.
Question:
  • On normal power side (utility power), no breaker is needed, but per NEC, if a breaker is installed between xfmr and fire pump, the breaker needs to be sized to handle motor inrush current, i.e., CB size = 6 x fire pump motor's FLA.
  • For generator power circuit, per NEC, the breaker to serve circuit to fire pump is not required to size to carry motor inrush current but = 2.5 X motor's FLA (article 430 for thermal magnetic breaker).
Question: when fire pump is on generator power, fire pump's inrush current never occur??? https://aperfectshinedetailing.com/
Click to expand...
Is a fire pump required to have a rated separation from other spaces in the building?
 
anbm said:
Fire pump controller/ats:
  • Normal power circuit comes from a tap to poco transformer's secondary side without protection.
  • Generator power circuit comes from a main emergency distribution panel (1st panel downstream of standby generator) and this circuit is protected by a breaker in panel.
Question:
  • On normal power side (utility power), no breaker is needed, but per NEC, if a breaker is installed between xfmr and fire pump, the breaker needs to be sized to handle motor inrush current, i.e., CB size = 6 x fire pump motor's FLA.
  • For generator power circuit, per NEC, the breaker to serve circuit to fire pump is not required to size to carry motor inrush current but = 2.5 X motor's FLA (article 430 for thermal magnetic breaker).
Question: when fire pump is on generator power, fire pump's inrush current never occur???
Click to expand...
The OCPD is sized for the locked rotor current, not the inrush.
 
Most of the rules in Art 695 are extracted from NFPA 20. Suggest you get a copy of what ever version of NFPA 20 you AHJ has adopted
 
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