Can someone help me understand the requirements of NEC 450.23 for putting an oil filled transformer on a roof? 450.23 will direct you to 450.27, and 450.27. The transformer has 2,427 gallons of FR3 oil, the building is a Type II with a Class A roof. This is a lower roof of an expansion, just an 8' x 20' electrical room, so not much roof space, no reasonable space to ground mount XFMR and egress door on each end of room. The client is insured by FM, Section 5-4 Transformers of FM Global Property Loss Prevention Data Sheets directs us to provide containment, but then goes on to state that the scope of the document is not to give the requirements for Environmental Protection and directs you to IEEE 980 Guide for Containment and Control of Oil Spills in Substations. I am just having a hard time understanding how to provide containment. How have folks done this in the past? What have they used?

Just curious. Is there a reason why you can't use a dry transformer? Also 2500 gallons is a lot of oil for a 1500 kVA transformer, are you sure that's correct?