Subject: 2015 IBC Section 504.4.1 Stair Enclosure Pressurization Increase Standby Power Options

Background:

In accordance with the Washington State Amendment to 2015 IBC Chapter 504.4.1, pressurization of the stair allows for an increase of one story for R-1/R-2 Type VA buildings. Legally required standby power shall be provided for stairway shaft pressurization equipment, elevators and lifts used for accessible means of egress, hoistway pressurization equipment and other life safety equipment that may be required.

Per the Washington State amendment to this section, legally required standby power shall comply with 2014 NEC Section 701.12, options (A), (B), (C), (D), (F), or (G). The state amendment excludes option E.

NEC defines the options as follows:

·  “A” – Storage Batteries

·  “B” – generator

·  “C” – UPS

·  “D” – Complete / Separate / By itself Utility Source

·  “E” – Tap Ahead of the Main

·  “F” – Fuel Cell

·  “G” – Unit Equipment

Per the State amendment, Option E “Tapping ahead of the Main” has been excluded from the standby power options. Prior to adoption of the state amendments in the 2015 IBC, City of Tacoma had a local policy amendment to this section that stated as follows:

4.1  For the purposes of this exception, standby power shall be provided for all exit enclosure pressurization systems used to meet subsection 4.3 above and shall be installed in accordance with sections 403.4.7 and 909.20.6.2, and the National Electric Code as adopted and amended by the City of Tacoma. Connection ahead of the main service disconnect switch shall be permitted for the standby power when standby power is not otherwise required to be provided by a generator.

Per this amendment, NEC Option E was specifically allowed.

Policy:

NEC Article 701.12 states that connecting ahead of the main for legally required emergency system power sources is permitted “Where acceptable to the authority having jurisdiction…”, The authority for this application is the local building official. Currently, fire pump services are connected ahead of the main in many installations in Tacoma. The Fire Code Official accepts this practice because they consider Tacoma Power to be a reliable source of power. TPU Electrical Inspection Services does not have an issue with the decision to utilize or not to utilize connections ahead of the main as the practice is an option available per electrical code. TPU Electrical Inspection Services will inspect for compliance with relevant code requirements regardless of the source of power. They are enforcing the 2017 edition of the NEC and the language contained in NEC Article 701.12 is the same as the 2014 NEC language.

Therefore, it shall be the policy of the City of Tacoma Building Official to continue to allow Option E, Tap Ahead of the Main for standby power, as by adoption of the 2015 State amendments, it was not the intention of the Building Official to disallow use of tapping ahead of the main which was allowed per our original amendment to this section.

City of Tacoma will work with the State Building Code Council to determine the reason behind excluding Option E in the State amendments and determine if it will become necessary to change this policy in the future.

Sue Coffman, Building Official, P.E., CBO

Planning and Development Services Department

City of Tacoma

File: R-1 R-2 shaft pressurization NEC options

Print Date: 1/8/2018 3:22 PM

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