Replies

1. 
   4Lorn1 | Jul 24, 2004 11:54pm | #1

   The number your look for is not the same for all ballasts. Ballasts out of the 60s are less efficient than more modern ones of the same general design.

   Electronic ballasts, particularly the more recent high frequency models bring efficiency to a whole new level. They also have favorable characteristics in terms of being much quieter, improved low temperature starting and almost no perceived flicker. These make them much easier to live with. Combined with the improved CRI, Color Rendering Index, lamps that are a lot closer to daylight and higher efficiency in terms of lumens per watt and you have a very nice fixture that would fit well in a living space.

   This is a big change from your fathers fixtures that were relegated to the shop and garage because they were loud, made colors and people look sick and often caused headaches. These benefits do not come cheap. Expect to pay several times more per fixture over the cheaper fixtures.

   A working figure on heat loss is 3% to 13% but better figures are often available through the various ballast manufacturers.

2. 
   TRice | Jul 27, 2004 04:53pm | #2

   Given the inherent inaccuracy of heat loss/gain calculations, the different efficiencies of various ballasts can be ignored. Standard engineering practice for commercial cooling load calculations: 1w = 3.4 btuh. If you took 7 fixtures x 4 lamps x 40 watts/lamp x 3.4 btuh/watt would be all of 9250 btuh load for lighting, in say 1200 to 1500 sf office space, you would also have approximately 20 people at 880btuh/per plus each with a pc at 150 to 250 watts per desk, plus copiers, printers, coffee makers, etc., then add in the required ventilation of 15 cfm/person and 75 cfm per toilet fixture, and depending on design conditions add approximately 50 btuh/cfm of outside air, add the solar load of a few windows and the plus or minus 10% of the 9250 of lighting load is insignificant.