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15 comments
Member

Join Date: Jul 2008
Posts: 8

circuit breaker requirement for fire pumps

07/20/2008 8:54 AM

can anybody help me on the continious current rating of the circuit breaker used for fire pumps ( with normal as well as essential incoming power supply). Shall i consider 1.15 times the FLC or shall i need to consider the Blocked rotor current aslo for the breaker selection(Continious current rating )?

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Guru
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#1

Re: circuit breaker requirement for fire pumps

07/20/2008 12:18 PM

The conductor is sized for 125% of the full load amps. The breaker is sized to carry the lock rotor amps or about 6 x the FLA.

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Guru

Join Date: Jun 2007
Location: chennai,India
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#2

Re: circuit breaker requirement for fire pumps

07/20/2008 12:52 PM

The fire pumps should not have any protective device.It is not recommended to have any circuit breaker,may be you can provide isolating switch for maintenance.

The concept behind this is the pump operates only during fire and it should not trip during emergency,therefore if the circuit breaker is provided it will trip under electrical fault conditions.Extinguishing the fire gets priority rather than electrical fault.

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Guru
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#4
In reply to #2

Re: circuit breaker requirement for fire pumps

07/20/2008 7:48 PM

The US NEC requires a breaker and It is sized to carry the Lock Rotor amps of the motor.

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#6
In reply to #2

Re: circuit breaker requirement for fire pumps

07/21/2008 12:45 AM

thank u for the information.

Also NFPA-20 have some specific requirement if we provide breakers(Cl.no.9.3.2.2.3.2.B)

ALSO one more information i need; if the fire pump is with one standby motor can we use a breaker sized for 1.15 times FLC?

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Guru

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#7
In reply to #6

Re: circuit breaker requirement for fire pumps

07/21/2008 12:56 AM

Normally there will be two fire pumps.One fire pump driven by Electrical Motor and the second one to be driven by the Engine.First Pump will be made to start first and when the water pressure is not adequate or falls below preset value, the second pump will be made to start .If such arrangement is there then ,may be the circuit breaker for the motor can be considered.In this instance , even if the first pump fails, there is a second one to come for the rescue.

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Ramesh,Freelance Electrical/automation Consultant
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#8
In reply to #7

Re: circuit breaker requirement for fire pumps

07/21/2008 1:08 AM

thank u for the instant feedback.

in case of a standby motor(electrically operated) shall we select the incoming breaker (Continious current)for 1.15 FLC?

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Active Contributor

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Location: Layton, Utah USA
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#12
In reply to #6

Re: circuit breaker requirement for fire pumps

07/21/2008 6:00 PM

If the motor is started "across the line" standard motor starter you should size the Breaker 175% - 250% Most of the time 175% is more than sufficient especially on a pump load.

Here's a NEC reference for fire systems for your info..... Section 430 is for motor loads....

695.4 Continuity of Power.
Circuits that supply electric motor-driven fire pumps shall be supervised from inadvertent disconnection as covered in 695.4(A) or (B).
(A) Direct Connection. The supply conductors shall directly connect the power source to either a listed fire pump controller or listed combination fire pump controller and power transfer switch.
Where the power source is supplied by on-site generator(s), the supply conductors shall connect to a generator disconnecting means dedicated for the purposes of serving the fire pump. The disconnecting means shall be located in a separate enclosure from the other generator disconnecting means.
(B) Supervised Connection. A single disconnecting means and associated overcurrent protective device(s) shall be permitted to be installed between a remote power source and one of the following:
(1) A listed fire pump controller
(2) A listed fire pump power transfer switch
(3) A listed combination fire pump controller and power transfer switch
For systems installed under the provisions of 695.3(B)(2) only, such additional disconnecting means and associated overcurrent protective device(s) shall be permitted as required to comply with other provisions of this Code. Overcurrent protective devices between an on-site standby generator and a fire pump controller shall be selected and sized according to 430.62 to provide short-circuit protection only. All disconnecting devices and overcurrent protective devices that are unique to the fire pump loads shall comply with 695.4(B)(1) through (B)(5).
(1) Overcurrent Device Selection. The overcurrent protective device(s) shall be selected or set to carry indefinitely the sum of the locked-rotor current of the fire pump motor(s) and the pressure maintenance pump motor(s) and the full-load current of the associated fire pump accessory equipment when connected to this power supply. The next standard overcurrent device shall be used in accordance with 240.6. The requirement to carry the locked-rotor currents indefinitely shall not apply to conductors or devices other than overcurrent devices in the fire pump motor circuit(s).
(2) Disconnecting Means. The disconnecting means shall comply with all of the following:
(1) Be identified as suitable for use as service equipment
(2) Be lockable in the closed position
(3) Not be located within equipment that feeds loads other than the fire pump
(4) Be located sufficiently remote from other building or other fire pump source disconnecting means such that inadvertent operation at the same time would be unlikely
(3) Disconnect Marking. The disconnecting means shall be marked "Fire Pump Disconnecting Means." The letters shall be at least 25 mm (1 in.) in height, and they shall be visible without opening enclosure doors or covers.
(4) Controller Marking. A placard shall be placed adjacent to the fire pump controller, stating the location of this disconnecting means and the location of the key (if the disconnecting means is locked).
(5) Supervision. The disconnecting means shall be supervised in the closed position by one of the following methods:
(1) Central station, proprietary, or remote station signal device
(2) Local signaling service that causes the sounding of an audible signal at a constantly attended point
(3) Locking the disconnecting means in the closed position
(4) Sealing of disconnecting means and approved weekly recorded inspections when the disconnecting means are located within fenced enclosures or in buildings under the control of the owner [20:9.2.3.3]

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Commentator

Join Date: Feb 2008
Location: Minnesota, USA
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#9
In reply to #2

Re: circuit breaker requirement for fire pumps

07/21/2008 10:31 AM

ramvinod, you are correct. After all, what good is a fire pump that trips a breaker, and who is supposed to run back into the building and reset it? I understand the pump should be hooked directly to the main with no short circuit or overload protection.

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Guru
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#15
In reply to #9

Re: circuit breaker requirement for fire pumps

08/13/2008 5:23 PM

ramvinod

you are located in the US and the NEC rules require a breaker.

NEC rules quoted from the Commoner's post

If this project is in the US, it is bound by the rules and regulations of the National Electric Code. Article 695.5 (B) of that code states, in full:

"The primary overcurrent protective device(s) shall be selected or set to carry indefinitely the sum of the locked rotor current of the fire pump motor(s) and the pressure maintenance motor(s) and the full load current of the associated fire pump accessory equipment when connected to this power supply. Secondary overcurrent protection shall not be permitted."

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Guru
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#3

Re: circuit breaker requirement for fire pumps

07/20/2008 7:35 PM

ramvinod's advice is essentially correct. The concept is, Fire Pumps must "run to destruction". If you are in the US, there are very specific rules in the National Electric Code that MUST be adhered to with regards to Fire Pump circuits. Canada uses very similar rules in the CEC. I strongly suggest that you read and fully understand all aspects of those rules before proceeding any further with this project, or hire someone with specific expertise in it. The ramifications of liability are enormous if you make the smallest of errors, because when a fire happens, insurance investigators get involved and start looking for people to blame. That's their primary job function.

If you are not in the US or Canada I do not know the code issues involved, but still, ramvinod's advice stands true.

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Active Contributor

Join Date: Oct 2007
Location: Philippines
Posts: 17
#5
In reply to #3

Re: circuit breaker requirement for fire pumps

07/21/2008 12:22 AM

1. Trip Setting of Fire Pump Controller can be up to 20 time motor full load current as permitted by NFPA20
2. Fire Pump Controller Circuit Breaker shall have a continous rating of not less than 115% of full load currrent and shall not trip when carrying up to 300% of motor full load current
3. The Fire Pump Controller Circuit Breaker shall trip between 8 and 20 seconds of the motor locked rotor current

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Guru
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Location: Alabama
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#10
In reply to #5

Re: circuit breaker requirement for fire pumps

07/21/2008 10:42 AM

Thats not true in the US, The code requires the breaker to withstand the lock rotor amps or about 6 times the full load amps.

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Power-User

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Location: Northeast Ohio, USA
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#11

Re: circuit breaker requirement for fire pumps

07/21/2008 12:13 PM

If this project is in the US, it is bound by the rules and regulations of the National Electric Code. Article 695.5 (B) of that code states, in full:

"The primary overcurrent protective device(s) shall be selected or set to carry indefinitely the sum of the locked rotor current of the fire pump motor(s) and the pressure maintenance motor(s) and the full load current of the associated fire pump accessory equipment when connected to this power supply. Secondary overcurrent protection shall not be permitted."

I believe that ssays it all.

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Guru

Join Date: Nov 2006
Posts: 663
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#13

Re: circuit breaker requirement for fire pumps

08/02/2008 10:04 AM

is it HT Or LT?

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Member

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Posts: 8
#14
In reply to #13

Re: circuit breaker requirement for fire pumps

08/03/2008 12:36 AM

It is LT(400V)

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JRaef (1); mini (3); nesubra (1); OpMan (1); popoy12345 (1); ramvinod (2); sparkybust (1); The Commoner (1); wareagle (4)

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