Construction Clearance Requirements

Clearances

Follow the guidelines below if you’re building a home, business or other structure near pad-mounted electrical equipment.

Pad-mounted equipment

You must maintain at least 10 feet between the front (doors) of any pad-mounted equipment, such as transformers, and other objects. You must maintain at least 3 feet of clearance from the back of the pad-mounted equipment.

Leave at least 10 feet of clearance above electrical equipment. For transformers that handle more than 1,000 kilovolt-amperes (kVA), leave at least 20 feet of overhead clearance.

Ask Idaho Power for clarification if you have any questions.

diagram of clearances for pad-mounted transformers

Non-combustible Walls

Combustible structures such as houses, garages and other buildings must be at least 10 feet from pad-mounted transformers. This clearance may be reduced to the 3-foot working clearance from a non-combustible wall. A 10-foot clearance is still required in front, to each side, and vertically of any door, operable window, air intake vent or path of egress located on a non-combustible wall or surface.

Cross-section diagram of non-combustible wall

Non-combustible walls must have:

  • A 1-hour fire rating for most commercial and industrial buildings.
  • A 3-hour fire rating for residences and businesses where people might be sleeping (hotels, etc.)

Exception: Non-operable windows (that don’t open) installed in a non-combustible wall require a 10-foot clearance in front but only 3 feet to each side.

Fire-resistant barriers

If it is not possible or practical to provide the required clearance between electrical equipment and a combustible building, the customer can install a fire-resistant barrier built of non-combustible materials that meets Idaho Power’s requirements and all applicable building codes.

Acceptable fire-resistant barriers are free-standing walls made of brick, concrete masonry unit (CMU) block or concrete that is located between the pad-mounted equipment and a combustible building or other surface.

Diagram of fire-resistant barrier

Consider the following when building a fire-resistant barrier:

  • Make sure the height and length of the barrier meet the requirements of each application.
  • Allow space for reasonable variations in the size of the equipment in case it needs to be replaced in the future.
  • The 10-foot clearance is measured as between the nearest point on the equipment and the wall, opening or path of egress.