Fire Pump Power Sources

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charlie b

charlie b

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Backup generator feeds a switchboard with two breakers in separate vertical sections. OK so far. One of the breakers (rated 200 amps) feeds the emergency ATS, and there is a panel (call it panel “E”) downstream of this ATS. The fire pump controller, with its own transfer switch, gets its normal power from a tap ahead of the main. The backup source to the fire pump comes from panel E. I have two problems with this arrangement.

  1. If the utility service is lost during a fire scenario, the fire pump will need the successful operation of two ATSs, in order for it to have power. I can’t think of a code that this violates, but I don’t like it.
  2. The fire pump (20 HP, 208/3, with a FLA of 59.4 amps) will be fed via the 200 amp breaker. That breaker can’t sustain 6 x FLA indefinitely, and it is not limited to short circuit protection only. I think this violates 695.6(B)(3). My question is whether that article comes into play for the backup power source. I can’t think of why it wouldn’t, but I thought I would ask.

Comments are welcome. FYI, I am doing a Peer Review, and this is one of my concerns with the project.
 
Based on the 2014 NEC

My thoughts

I would look at 695.4 (B) (3) (b) which states the disconnecting means for an on site generator used as the alternate power source shall be installed in accordance with 700.10(B)(5) for emergency circuits......

700.10(B)(5) talks about the seperate vertical sections etc.....

Let me know what you think
 
charlie b said:
Backup generator feeds a switchboard with two breakers in separate vertical sections. OK so far. One of the breakers (rated 200 amps) feeds the emergency ATS, and there is a panel (call it panel “E”) downstream of this ATS. The fire pump controller, with its own transfer switch, gets its normal power from a tap ahead of the main. The backup source to the fire pump comes from panel E. I have two problems with this arrangement.

  1. If the utility service is lost during a fire scenario, the fire pump will need the successful operation of two ATSs, in order for it to have power. I can’t think of a code that this violates, but I don’t like it.
  2. The fire pump (20 HP, 208/3, with a FLA of 59.4 amps) will be fed via the 200 amp breaker. That breaker can’t sustain 6 x FLA indefinitely, and it is not limited to short circuit protection only. I think this violates 695.6(B)(3). My question is whether that article comes into play for the backup power source. I can’t think of why it wouldn’t, but I thought I would ask.

Comments are welcome. FYI, I am doing a Peer Review, and this is one of my concerns with the project.
Click to expand...

1. The fire pump ATS should be fed from a tap ahead of the panelboards.
2. Doing 1. will take care of the breaker size issue.
 
The switchboard immediately downstream of the generator does have separate vertical sections for the 200 amp breaker serving emergency loads and the 800 amp breaker serving optional standby loads. That much is OK. The normal feed to the fire pump is a tap ahead of the main from the utility. That much is also OK. Should the backup feed to the fire pump come from a tap ahead of the 200 amp breaker on the generator's switchboard? Would it be a code violation if it is not connected there?
 
charlie b said:
Backup generator feeds a switchboard with two breakers in separate vertical sections. OK so far. One of the breakers (rated 200 amps) feeds the emergency ATS, and there is a panel (call it panel “E”) downstream of this ATS. The fire pump controller, with its own transfer switch, gets its normal power from a tap ahead of the main. The backup source to the fire pump comes from panel E. I have two problems with this arrangement.

  1. If the utility service is lost during a fire scenario, the fire pump will need the successful operation of two ATSs, in order for it to have power. I can’t think of a code that this violates, but I don’t like it.
  2. The fire pump (20 HP, 208/3, with a FLA of 59.4 amps) will be fed via the 200 amp breaker. That breaker can’t sustain 6 x FLA indefinitely, and it is not limited to short circuit protection only. I think this violates 695.6(B)(3). My question is whether that article comes into play for the backup power source. I can’t think of why it wouldn’t, but I thought I would ask.

Comments are welcome. FYI, I am doing a Peer Review, and this is one of my concerns with the project.
Click to expand...

1) It meets the letter of the NEC 695 and NFPA 20. Many designers though prefer to have a genset with a separate breaker for the fire pump. All the major genset players offer this as an option.
2) The alternate source when using an on-site generator is not allowed to use the 6X rule for over current let alone be required. See 695.4(B)(2)(b).
 
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