UFC 3-520-05, Stationary and Mission Batteries (1 May 2015, Change 2, 9 January 2020)

Overview

UFC 3-520-05 is a complete revision and reissuance of the Stationary Battery Areas document dated 14 April 2008; this copy includes Change 2 of 9 January 2020. It aims to provide technical requirements for enclosed battery areas, bring together the multi-discipline architectural, electrical, mechanical, civil, fire protection and plumbing requirements for battery area layout, and avoid over-design by applying industry standards first. It applies to DoD-owned or leased facilities, takes precedence over any other conflicting document, applies to new construction and major renovation, and does not require renovating existing installations solely to meet it. For battery selection, sizing and application it refers to UFC 3-520-01, which prohibits lithium batteries for stationary use in occupied facilities.

In Chapter 2 the architectural criteria are: NFPA 1 criteria apply to all stationary batteries of 48 VDC nominal or higher regardless of electrolyte volume; different chemistries go in separate rooms with no direct access between them. Battery cabinets (including UPS cabinets) must be commercial products, UL listed or third-party verified, with at least 200 mm (8 in.) working clearance around the batteries or on drawout racks. An electrolyte spill is an unintended release exceeding 1.0 litre; vented lead-acid and NiCd cabinets need integral spill containment, permanent containment must resist continuous exposure to 70% electrolyte concentration, and VRLA needs none. Seismic category A needs no cell restraints, B side restraints and C-F heavy-duty construction; cells over 50 lb (23 kg) need lifting equipment.

The mechanical criteria require hydrogen below 1% concentration, calculated for the worst case of simultaneous boost (equalise) charging of all batteries, using for VRLA a maximum generation rate of 1.27 x 10^-7 m3/s (2.69 x 10^-4 cfm) per charging ampere per cell at 25 C. Battery room exhaust ducts run directly to the exterior by the shortest route, contain no fire dampers, need continuous fire-rated duct wrap, and discharge at least 6 ft from exterior walls and roofs, 10 ft from operable openings and 10 ft above grade; the fan must be ANSI/AMCA 99-16 type A with a non-sparking wheel. The optimal operating temperature for lead-acid and NiCd is 68-77 F (20-25 C) and lead-acid areas are kept below 85 F (29 C).

Electrical criteria require overcurrent protection for each battery string, a disconnect near the room entrance or a shunt-trip device for DC conductors leaving a separate battery room, temperature-compensated charging for VRLA based on battery temperature, bonding of racks and cabinets with at least #6 AWG conductors, lighting of at least 300 lux (30 fc) with pendant or wall fixtures that do not collect gas, voltage alarms, current and ground detection, and eyewash within 20 ft of the battery. Fire protection requires a sprinkler in each battery room where the facility needs a wet-pipe system, with the flow switch removing power from the chargers served; smoke detection and portable extinguishers are not required.

Chapter 3 covers military mission lithium batteries and excludes portable commercial cells that are UL listed, 18 V or less and under 100 Wh. Lithium batteries are treated as hazardous: the preferred storage is an unoccupied segregated shelter next to the building, or dedicated fire-barrier rooms if inside, with charging rooms separated from storage and two egress routes with panic hardware. Lithium mission battery rooms need emergency exhaust of at least 12 air changes per hour to hold explosive gases below 25% of the lower explosive limit on thermal runaway, and dedicated cooling holding 65 F (18.3 C). A lithium risk assessment is in Appendix C. The document is DoD-specific and gives little support for modern Li-ion UPS designs.

Key points

1. NFPA 1 criteria apply to all stationary batteries of 48 VDC nominal or higher regardless of electrolyte volume; each chemistry goes in its own room.
2. Battery cabinets (including UPS cabinets) must be UL listed or third-party tested and provide at least 200 mm (8 in.) working clearance.
3. An electrolyte spill is a release over 1.0 litre; containment must resist continuous exposure to 70% electrolyte concentration; VRLA batteries need no spill containment.
4. Ventilation must keep hydrogen below 1%, using a VRLA generation rate of 1.27 x 10^-7 m3/s (2.69 x 10^-4 cfm) per charging ampere per cell at 25 C for worst-case boost charging.
5. Battery exhaust discharge must be at least 6 ft from exterior walls and roofs, 10 ft from operable openings and 10 ft above grade, with no fire dampers in the exhaust duct.
6. Optimal lead-acid and NiCd temperature is 68-77 F (20-25 C); lead-acid battery areas should be kept below 85 F (29 C).
7. Battery racks and cabinets are bonded with at least #6 AWG conductors, room lighting is at least 300 lux (30 fc) and eyewash is within 20 ft of the battery.
8. UFC 3-520-01 prohibits lithium batteries for stationary applications in occupied facilities; this UFC covers lithium only for military mission batteries.
9. Lithium mission battery rooms need emergency exhaust of at least 12 air changes per hour to hold explosive gases below 25% of LEL on thermal runaway, and dedicated cooling holding 65 F (18.3 C).
10. Seismic category A needs no cell restraints, B side restraints and C-F heavy-duty racks; cells over 50 lb (23 kg) need lifting equipment.

Using it in design

• Set battery room scope by NFPA 1 (all stationary batteries of 48 VDC and above), put different chemistries in separate rooms, and avoid unrelated services and direct access; do not use the room for storage.
• For vented lead-acid and NiCd plan cabinets with integral spill containment or a containment structure resistant to 70% electrolyte (sized for releases over 1.0 litre); note VRLA needs none, and keep neutralising and absorbent materials outside the room.
• Calculate hydrogen ventilation for worst-case boost charging, using the 1.27 x 10^-7 m3/s per ampere per cell VRLA rate or manufacturer data, check the 1% limit inside cabinets too, and do not put fire dampers in the exhaust duct.
• Place the exhaust discharge 6 ft from exterior walls and roofs and 10 ft from operable openings and grade, and size cooling to hold lead-acid areas below 29 C, ideally 20-25 C.
• Add per-string overcurrent protection, an entrance disconnect or shunt trip, battery-temperature-based compensated charging for VRLA, #6 AWG bonding, 300 lux lighting, voltage and current alarms and eyewash within 20 ft, and have the sprinkler flow switch remove charger power.
• Do not treat this UFC as support for modern Li-ion UPS designs, since UFC 3-520-01 prohibits stationary lithium in occupied buildings; consult other codes and standards for lithium.

Who should read it

Electrical, mechanical and fire protection engineers designing battery rooms for UPS and switchgear batteries in data centres and other facilities.

Document contents

1. Introduction
2. Purpose and Scope
3. UFC Hierarchy
4. Upgrades and Modifications to Existing Systems
5. Exclusions (excluded battery applications, lithium batteries, electric vehicle charging)
6. Application (battery types, facilities, conflicts, compliance)
7. Safety
8. References
9. Stationary Battery Design Criteria
10. General
11. Architectural Requirements (location, cabinets, spill control, racks, seismic design)
12. Mechanical Requirements (ventilation, battery exhaust system, thermal management)
13. Electrical Requirements (overcurrent protection, bonding, lighting, instrumentation and control)
14. Emergency Facilities
15. Fire Protection Requirements (sprinkler system, portable fire extinguishers)
16. Lithium Battery Design Criteria
17. Architectural, Ventilation, Exhaust and Thermal Management (lithium)
18. Fire Protection, Battery Charging Equipment, Lighting (lithium)
19. Appendix A References
20. Appendix B Stationary Battery Applicability
21. Appendix C Lithium Batteries Risk Assessment

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Publication details

Authors

Naval Facilities Engineering Command (NAVFAC); U.S. Army Corps of Engineers (USACE); Air Force Civil Engineer Center (AFCEC)

Publisher

U.S. DoD (UFC)

Year

2020

Document language

English

Source type

Government / public

Access

Open licence — downloadable

Licence

U.S. public domain — U.S. Government work; free to reuse

Licence evidence

www.copyright.gov

Citation