Tier Standard: Topology

Overview

Tier Standard: Topology separates four Tier classifications by increasing numbers of redundant capacity components and distribution paths, and includes the performance confirmation tests used to determine compliance. A separate commentary gives example configurations. The document is free to download but requires agreeing to terms through a form, so this page relies on the public abstract and widely published requirements; the full text was not read. The most quoted provisions concern the engine generator. For Tier III and IV the generator is treated as the primary power source and must have no limit on consecutive run hours at N demand.

That means a continuous rating, or a prime or standby rating derated so that no runtime limit applies. In other words, the kVA figure on the nameplate is not enough; the rating class it is quoted under decides Tier compliance. On fuel, the widely published baseline is at least 12 hours of on-site storage at N design load, with many sites choosing 24-72 hours. For Tier III the fuel system (tanks, pumps, piping) must itself be concurrently maintainable; for Tier IV it must be fault tolerant and compartmentalized.

A fuel path with a single pump or a single fill point therefore cannot reach Tier III. The limit of the source is access: because it needs registration, the full text was not used and the fuel hours and generator provisions come from secondary sources. Treat these values as defaults until confirmed against a licensed copy or Uptime. The document should be read together with Uptime's separate Operational Sustainability standard, since topology alone does not guarantee operating outcomes.

Key points

1. Four classifications differ by increasing redundant capacity components and distribution paths; performance confirmation tests are included
2. Engine generators are the primary power source for Tier III/IV
3. Generators must have no limit on consecutive run hours at N demand (continuous rating, or derated prime/standby with no runtime limit)
4. Minimum 12 hours of on-site fuel at N design load is the baseline; many sites choose 24-72 h
5. Tier III: the fuel system (tanks, pumps, piping) must be concurrently maintainable
6. Tier IV: the fuel system must be fault tolerant and compartmentalized
7. Download is free but needs a form; abstract and widely published requirements were used

Using it in design

• For Tier III/IV targets, accept only generator ratings flagged 'continuous' or unlimited-hours in the sizing module
• If the user picks ISO 8528 'standby' or 'prime', require a derating factor or flag non-compliance
• Default fuel autonomy to 12 h at N load, with 24/48/72 h presets
• Check the fuel topology for N+1 pumps and two fill paths when Tier III is the intent

Who should read it

Electrical design engineers, consultants specifying generators and fuel systems, and owners of Tier-targeted projects.

Related standards

• ISO 8528-1
• NFPA 110
• TIA-942
• ANSI/BICSI 002

Publication details

Authors

Uptime Institute

Publisher

Uptime Institute

Year

2018

Document language

English

Source type

Industry body

Access

Citation only

Licence

Copyright retained; citation only — the publisher’s terms apply to the original document

Citation