Clarification on Roof Clearance for Medium- to Low-Voltage Oil Transformers in Vaults
- Thread starter julianov
- Start date
Ohm2
Member
- Location
- Washington
- Occupation
- Electrician
25ft may be reasonable considering safety, but you could consult with a local official and justify a smaller clearance.
Elect117
Senior Member
- Location
- California
- Occupation
- Engineer E.E. P.E.
It also depends on who owns the transformer. A utility might require that distance so that they can get a crane situated to lift it in and out. Or because they use different flammability oils. Or they were sued once for burning a building down or loss of life. By creating a separation they can probably make it safer.
Also, for oil filled transformers in vaults, the room needs to be 3 hour rated (NEC 450.23 - 450.41). With less than flammable and non flammable oil that can be reduced to 2hr rating.
Most oil transformers require special methods for fire suppression. The best case scenario is a firefighter knows to use special foams. Worse case, they use water and it spreads. Hence the containment for the oil spill.
Also, for oil filled transformers in vaults, the room needs to be 3 hour rated (NEC 450.23 - 450.41). With less than flammable and non flammable oil that can be reduced to 2hr rating.
Most oil transformers require special methods for fire suppression. The best case scenario is a firefighter knows to use special foams. Worse case, they use water and it spreads. Hence the containment for the oil spill.
In this case, the transformer is located outside, adjacent to the building, with a 15-foot roof, while the transformer itself is 8 feet tall. What seems strange to me is that the NEC does not specify distances, while FM does provide guidelines but does not ensure that they are regulatory measurements