Architects & Engineers - Transformer Pad Specs | Alabama Power

Transformer Pad Specs


Eliminate construction obstacles with these specs for three-phase, pad-mounted transformers.

When a client requests underground service, one of the most common problems architects and engineers face is insufficient space. To help make your design planning a little easier, use these specifications for three-phase, pad-mounted transformers. Be sure to confirm the pad location with your local power company engineer prior to construction.

General Specifications for Pad Location

  1. Customer's service entrance cable and conduits should be installed in the open window of the concrete pad in the shaded area shown. Conduits should be installed starting at the extreme right-hand side of the window. Conduits should not be installed near the left-hand dimension of the shaded customer conduit window unless absolutely necessary.
  2. Grounding is to be provided by enhanced grounding consisting of 100 feet of #2 copper 7-strand conductor installed in the bottom of the trench and/or 30 foot sections of ground rod installed in both the primary and secondary sides of the concrete pad window. The ground rod locations are not dimensioned to allow maximum flexibility in locating the ground rods, but the separation between ground rods should be as great as possible.
  3. The transformer pad should not be located near fire hydrants, fire escapes, doors, windows, ventilation ducts, or under building overhangs. If possible the pad should be installed on ground that slopes away from the building. There should be no above ground obstructions such as air conditioners, walls, shrubbery, trash bins, etc. in front of the transformer location. The transformer location must be accessible by large truck or crane.
  4. There must be clear area around the transformer as detailed in the drawing below. The 10' x 10' area at the rear of the pad is necessary for the proper operation of the bayonet fuse of the transformer.