A pad-mounted distribution transformer serving single-phase loads, used for residential underground service and small commercial loads. IEEE C57.12.38 standardizes units rated 250 kVA and smaller (high voltage 34,500 GrdY/19,920 V and below); larger single-phase pad-mounted ratings such as 333 and 500 kVA are manufactured to the general requirements of IEEE C57.12.00 and manufacturer specifications.