Skip to main content

Reliable Electrical Power for Fire Pumps and Backup Power

* Note that the 2016 edition of NFPA 20 changed the 4-hour to 10-hours of continuous outage *

When do you need backup power for an electric fire pump?  The simple answer is when the power is "reliable".  Of course the word reliable means a lot of different things to different people.  Interestingly, NFPA 20 did not define reliable power until the 2007.  Thankfully the committee did agree on the following language:
NFPA 20-2010
A.9.3.2 A reliable power source possesses the following characteristics:
(1) The source power plant has not experienced any shutdowns longer than 4 continuous hours in the year prior to plan submittal. NFPA 25, Standard for the Inspection, Testing, and Maintenance of Water-Based Fire Protection Systems, requires special undertakings (i.e., fire watches) when a water-based fire protection system is taken out of service for longer than 4 hours. If the normal source power plant has been intentionally shut down for longer than 4 hours in the past, it is reasonable to require a backup source of power.
(2) No power outages have been experienced in the area of the protected facility caused by failures in the power grid that were not due to natural disasters or electric grid management failure. The standard does not require that the normal source of power is infallible. NFPA 20 does not intend to require a back-up source of power for every installation using an electric motor–driven fire pump. Should the normal source of power fail due to a natural disaster (hurricane) or due to a problem with electric grid management (regional blackout), the fire protection system could be supplied through the fire department connection. However, if the power grid is known to have had problems in the past (i.e., switch failures or animals shorting a substation), it is reasonable to require a back-up source of power.
(3) The normal source of power is not supplied by overhead conductors outside the protected facility. Fire departments responding to an incident at the protected facility will not operate aerial apparatus near live overhead power lines, without exception. A back-up source of power is required in case this scenario occurs and the normal source of power must be shut off. Additionally, many utility providers will remove power to the protected facility by physically cutting the overhead conductors. If the normal source of power is provided by overhead conductors, which will not be identified, the utility provider could mistakenly cut the overhead conductor supplying the fire pump.
(4) Only the disconnect switches and overcurrent protection devices permitted by 9.2.3 are installed in the normal source of power. Power disconnection and activated overcurrent protection should only occur in the fire pump controller. The provisions of 9.2.2 for the disconnect switch and overcurrent protection essentially require disconnection and overcurrent protection to occur in the fire pump controller. If unanticipated disconnect switches or overcurrent protection devices are installed in the normal source of power that do not meet the requirements of 9.2.2, the normal source of power must be considered not reliable and a back-up source of power is necessary.

Interestingly for those of you who are insured by FM Global, the requirements are actually less stringent.
FM 3-7 (May 2010)
2.7.1.2 Supplement unreliable power sources with a second, independent source of power, such as an emergency generator or alternate utility connection, or provide a diesel engine-driven pump.
A reliable power source has infrequent power disruptions from environmental or man-made conditions. An electric power source that has disruptions lasting longer than 8 hours three or more times in a 12-month period is considered unreliable. More frequent short-term outages would also be considered unreliable.
The backup power can be from either an emergency generator or from a separate power system (unlikely).  So don't forget to select or a transfer switch or else change to a diesel engine driven fire pump.


Popular posts from this blog

Installation of Diesel Fuel Tanks for Fire Pumps (OLD)

This article is based upon 2009 IFC codes and is obsolete. See newer version here:  https://blog.anvil-fire.com/2024/03/installation-of-diesel-fuel-tanks-for.html After you have determined the size of fuel tank you need for a diesel fire pump, what are the general requirements for installation?  Assuming that you are under under the International Building/Fire Codes, you would go through the following chain of code references: IFC (2009 edition) 3401.2 Nonapplicability. This chapter shall not apply to liquids as otherwise provided in other laws or regulations or chapters of this code, including: ... (3) Storage and use of fuel oil in tanks and containers connected to oil-burning equipment. Such storage and use shall be in accordance with Section 603 . For abandonment of fuel oil tanks, this chapter applies. IFC (2009 edition) 603.1 Installation. The installation of nonportable fuel gas appliances and systems shall comply the International Fuel Gas Code. The installation of all oth

Diesel Exhaust Requirements

The exhaust from a diesel engine driving a fire pump is an often-overlooked item.  The high heat put out by the exhaust is a hazard to occupants and can greatly contribute to overheating the room itself. NFPA 20 (2013 edition), section 11.5 covers "Engine Exhaust" and should be carefully reviewed. However as a starting point, the following items should be considered. Exhaust Discharge Location The first step is to determine where you are going to discharge the exhaust gases. NFPA 20 section 11.5.3 for "exhaust discharge location" has the generic common-sense requirements of do not discharge where you might hurt people, damage the building, or directed on combustible materials. But very little specific requirements are provided. There is a loose reference in NFPA 20 back to NFPA 37 ( Standard for the Installation and Use of Stationary Combustion Engines and Gas Turbines ). In addition, the International Mechanical Code (IMC) section 915.1 directs us back to NFPA 3

Fire Pump Rating (Size) Selection

Fire pump sizing is not like commercial pump sizing. We don't care about efficiency, and you order pumps in only specific sizes. This article touches upon some items to consider when picking a fire pump. In general, the first step is determining your system demand point. Discussion of how exactly you determine this is beyond the scope of this article and has a lot of nuance depending upon your site-specific needs. However, for simplicity let's assume that you have a dry-system in an attic with a demand point of 305 gpm (2535 sq ft x 0.10 gpm/sq ft x 1.20 overflow/imbalance factor). Rated Flow (gpm) Sizing The first item you must specify is the pump flow rate. Per NFPA 20 (2013 edition) table 4.8.2 pumps are only allowed to be listed with the following flow rates in gpm: 25, 50, 100, 150, 200, 250, 300, 400, 450, 500, 750, 1000, 1250, 1500, 2000, 2500, 3000, 3500, 4000, 4500, 5000 So with our example demand of 305 gpm, would you go with a 300 or 400 gpm rated fire pump?