I am writing this article in my hotel room in Anchorage, Alaska, where I just finished a two-day workshop on the changes to the 2011 National Electrical Code (NEC). A number of engineers at the seminar were very interested in the fire-pump requirements as outlined in 695.3 and 695.4. I pointed out that the revised arrangement of Article 695 makes a more user-friendly approach for fire-pump installations. So, I thought I would summarize the discussion here.
Power source(s)—695.3(A) through (F)
I told the class that 695.3(A) through (F) cover power supplies to fire pumps, and extensive revisions were made to these section subdivisions. The power supply for a fire pump must be reliable. To be considered a reliable power source, the power must not shut down more than four hours within a year according to NFPA 20: A.9.3.2(1). The power source must have adequate capacity to carry the locked-rotor currents of the fire-pump load and accessory equipment indefinitely. If a fire occurs, the requirements in 695.3 of the 2011 NEC are there to ensure the fire pump is not disconnected and continues to operate until failure.
Section 695.3(A)(3) is new and governs the requirements for a fire-pump feeder that is tapped from the supply side of a service connection. I also mentioned that a dedicated fire-pump feeder can be derived from a dedicated service or from a tap properly made ahead of the service main disconnecting means and as described in NEC 695.3(A)(1) and NFPA 20 9.2.2(1), which actually deals with the “Electrical Utility Service Connection” in an electrical supply system.
This section has been rearranged to provide two provisions that deal with a combination of power sources. For example, 695.3(B)(1) recognizes individual sources of two or more power supplies that are, under certain conditions, capable of supplying fire-pump equipment. Section 695.3(B)(2) permits one of the sources of power from 695.3(A) with an on-site standby generator as permitted in 695.3(D) and NFPA 20 9.3.4.
Multibuilding campus-style complexes—695.3(C)
This new section covering multibuilding campus-style installations contains language that provides better clarity pertaining to requirements. Direction is also outlined where the power supplies mentioned in 695.3(A) is not practicable for a multibuilding campus-style fire-pump installation. Section 695.3(C)(1) covers the installation of two feeder supply sources from separate utility services as more than one means of fire-pump power. However, 695.3(C)(2) allows a feeder with an alternate power source (such as a generator set) that is completely independent of the feeder power source to be utilized. Section (C)(3) of 695.3 is important, for it requires that overcurrent-protection devices (OCPDs) in each disconnecting means are selectively coordinated with any other supply-side OCPDs.
Section 695.3(E) is the existing 693.3(B)(3) of the 2008 NEC that pertained to power-supply sources. Relocating it permits its requirements to be applied to the multiple power sources of both 695.3(B) and 695.3(F) that covered multibuilding campus-style installations.
Provisions of this section correlate with the NEC and NFPA 20 requirements, which prohibit the use of phase converters in fire-pump installations. Phase converters per Article 455, when used in a fire-pump application, can cause operational problems due to misbalancing that can occur with varying load conditions.
Continuity of power—694.4
This section has been divided into three major sets of requirements pertaining to a number of disconnecting means, overcurrent-device selection and disconnecting means. Sections 695.4(A) or (B) governs the proper supervision that helps prevent inadvertent disconnection of circuits supplying electric motor-driven fire pumps. The main objective of 695.4 is to define the locations where the power supply to the fire pump is automatically or manually interrupted. Section 695.4(B)(1) is subdivided into levels (a) through (c), which covers the general requirements for disconnecting and providing OCPDs for the feeder sources as well as rules for on-site standby-generator applications. Section 695.4(B)(2), levels (a) and (b), outline the requirements for sizing the OCPDs that have enough capacity to allow the fire-pump equipment to operate indefinitely. The revised text permits the OCPD to be rounded up to the next available size. Section 695.4(B)(3) and subdivided levels deal with the disconnect itself.
Before designing and installing a fire pump, electrical personnel must review and understand the revisions and changes that took place in Article 695 of the 2011 NEC.
STALLCUP is the CEO of Grayboy Inc., which develops and authors publications for the electrical industry and specializes in classroom training on the National Electrical Code and other standards, including those from OSHA. Contact him at 817.581.2206.