Liquid filled transformer builing seperation requirements question

[rockman7892]

I've been involved in a lot of projects where liquid filled transformers are installed adjacent to a building and usually follow separation requirements from FM Global Property Loss standard (5ft separation less than 5000 gallons). A lot of these installations involve a new E-House or IPA building which contain secondary MV/LV switchgear which are fed from secondary of adjacent transformer outside of building.

An interesting question came up the other day regarding the required 5ft separation between buildings vs the allowance for close-coupling between transformer and NEMA 3R sheltered isle switchgear. (Assuming there are no separation requirements with sheltered isle gear since I've seen several installations as such).

So that brings up the question in my mind as to the main differentiator between an E-House and a sheltered isle enclosure? In some cases the argument has been made that the building is used for nothing more than to provide enclosure and climate conditioning for switchgear (no occupancy).

Is there an official definition or differentiator that defines a building vs a sheltered isle structure and thus the need to follow FM global requirements for buildings but not sheltered isle enclosures? Something to do with building code perhaps?

 

[dpc]

1. Occupancy classification of the structure or building.
2. Transformer "vault" rating (NEC) and fire wall ratings.

 

[dpc]

Also, high fire point liquid in transformers.

 

[rockman7892]

dpc

Thanks for responses.

This is an application with a modular pre-fab electrical building (IPA). (Not a vault). Does the FM global requirements take into consideration the occupancy classification of the building/structure (Occupied vs unoccupied). I did not see where it delimitated that and always understood it to be based on the fact that if the transformer was in close proximity to any building of stated construction materials (regardless of occupancy) then the standards and limitation applied?

 

[FacEngrPE]

The data sheet was recently updated. FM Global Property Loss Prevention Data Sheets 5-4 Transformers July 2019 Interim Revision July 2021 (Free to download)

The FM standard talks about separation to Main Building, I contend the transformer associated switching house is not a main building. FM will want to take some loss protection measures to reduce loss at the switch gear, and hopefully protect the building. If you are a client of the most reputable insurers (like FM), they have an risk engineering office that will review design documents and generally make sensible comments.