EPA Calculation

The EPA or Effective Projected Area describes the area of a luminaire or bracket which is exposed to the wind.

This is how you can calculate the EPA to find the pole most suitable for your local wind conditions, with the luminaire or luminaire cluster you selected:

  • Calculate the EPA for the luminaire or luminaire/bracket cluster
    • For single luminaire units, refer to the EPA specified in the technical sheet of the luminaire provided in the Schréder luminaire catalogue.
    • For luminaire/bracket clusters:
      For example, an ALU-150MH-T6-DSYM-120-RAL9007 luminaire with a CAL-2-2-RAL9007 bracket for which an 8 ft (2.44 m) aluminum round pole is required:
    • Take the luminaire EPA.
      For ex. 1.33 sq.ft. for an ALURA luminaire.
    • On the matrix below, locate the multiplying factor corresponding to the required configuration :
      EPA calculation multiplying factor

      For ex., for configuration 2 take multiplying factor 2.00.
    • Multiply i. and ii.
      In our example: 1.33 X 2.00 = 2.66 sq.ft.
    • Take the bracket EPA for the required configuration.
      For ex. 1.78 sq.ft. for the CAL-2-2 (Casura) bracket.
    • Add iii. and iv. In our example:
      2.66 + 1.78 = 4.44 sq.ft.

    → The total EPA for the ALU-150MH-T6-DSYM-120-RAL9007 luminaire and CAL-2-2-RAL9007 bracket is 4.44 sq.ft.

  • Using the wind chart, verify the annual maximum wind speed for the area where the luminaire is to be installed.
    For ex. a maximum wind speed of 70 mph.
  • 3. Select a pole whose EPA (at the local wind speed determined in 2.) is either higher or equal to the luminaire’s or cluster’s EPA calculated in 1.
    For ex. the 8 ft (2.44 m) aluminum round pole most suitable for :
  • a luminaire/bracket cluster of 4.44 sq.ft. (see 1.)
  • in an area with 70 mph maximum wind speed (see 2.) is: an APR3F-8.

The APR3F-8 pole has an EPA of 5.9 sq.ft. for 70 mph winds, which is higher than 4.44 sq.ft. (the EPA of the cluster).

More information: AASHTO Standard Specifications for Structural Supports for Highway Signs, Luminaires and Traffic Signals.