As soon as the public is present, the stake is no longer the equipment but the evacuation. Fire behaviour, the F1 · E2 · C2 classes, hospital redundancy: the real selection criteria.
A building open to the public, hospital, school, shopping centre, hotel, public-facing offices, sits under a demanding fire-safety regime, because the stake is not the equipment but the evacuation of people. Concretely, that moves the cursor on three points: the transformer's fire behaviour, its location in the building, and the continuity of supply to the safety installations. The precise requirements depend on the building's type and category and on the texts in force: they are validated with your design office and the safety authorities, never from memory.
The underlying question is simple: what happens in an internal fault? An oil-immersed transformer contains a flammable liquid, hence, indoors, requirements on a fire-rated room, retention and sometimes suppression. The cast resin dry-type has no liquid: rated F1 (self-extinguishing, low smoke and halogen emission), it installs indoors with no retention pit and no dielectric fire risk. That is why it is the default choice in public buildings and hospitals, while oil-immersed remains king outdoors.
The alternative exists: an ester-filled oil-immersed unit (high fire point, biodegradable) answers some fire-safety files. The right call is made with your risk analysis, not with a general rule, and we price both.
F1, fire behaviour: self-extinguishing, limited smoke and toxic-gas emission; the expected class wherever the public is present. E2, environment: withstands severe condensation and pollution (basements, humid technical rooms). C2, climate: operates and travels down to −25 °C. The F1·E2·C2 trio is the usual specification for demanding indoor sites. It is requested explicitly, and verified on the test report.
In a hospital the requirement goes beyond fire safety: some circuits must not stop. That translates into redundant architectures (two transformers, each able to absorb the other's load), articulation with generating sets and UPS, and sometimes specific earthing regimes in medical locations. The practical consequence on the transformer side: two machines running at partial load, hence no-load losses weighing 24/7, the classic argument for going beyond minimum Tier 2.
General overview; the exact requirements depend on the building's type and category and the texts in force, validated with your design office and the safety authorities.
No: it is not a blanket ban but a safety file. An oil-immersed unit indoors triggers requirements on the room, retention and sometimes suppression, which weigh in cost and footprint. That is why F1 cast resin nearly always wins in practice; ester is an intermediate route in some files.
F1 covers the transformer's own fire behaviour. The building's safety file can add measures on the room, detection and safety-supply continuity: F1 is the necessary class, the safety file decides the rest.
Usually in redundant pairs, each able to pick up the other's load, so both run at partial load in normal operation. No-load losses then weigh around the clock, the classic argument for going beyond minimum Tier 2.
Your design office and the safety authorities for the building (safety commission, control office in France). Requirements depend on the building's type and category and the texts in force; our specification aligns on their file.