Ballast power

A project I administered received this comment: Please provide the ASHRAE/IESNA Standard 90.1-2004 User's Manual, Lighting Compliance Documentation including the task lighting and ballast power consumption. The electrical engineer responded with this question: We can include task lighting in the comcheck calculation. However, I was looking for clarification on the ballast power consumption. Where and how would this factor be included? This was GBCI's response to the above question: The wattage of luminaires with permanently installed or remote ballasts should be the operating input wattage of the maximum lamp/ auxiliary combination based on values from the auxiliary manufacturers’ literature or recognized testing laboratories; or it should be the maximum labeled wattage of the luminaire. The project team can also refer to the data provided for common florescent and compact florescent fixtures in the Lighting Reference Section the ASHRAE 90.1-2004 User’s Manual. This information may be entered either in the Comcheck calculation or the ASHRAE/IESNA user’s manual documentation, either is acceptable.

The wattage is the combination of the lamp wattage and the ballast factor. So a 32 watt fluorescent with a BF of 0.9375 yields 30 watts. Conversely a 100 watt metal halide and a BF of 1.1 yields 110 watts. Generally you want to use the combination instead of the maximum labeled wattage.