lightCALC advanced – Step 1 – Luminaire

Once you have completed your product selection process, and the lightCALC advanced window is open, you will see your selected product displayed.  Within this window is a box labeled Light Loss Factor (LLF).  In order to perform an accurate calculation, it is necessary to adjust this value to one specific to the luminaire, lamp and ballast you desire to use.  Failure to adjust this factor properly will result in inaccurate results.

Choosing the correct Light Loss Factor (LLF) is not difficult, but may require data from other resources.

Click here to see the LLF Matrix to determind Light Loss Factor. LLF Matrix

The equation to determine LLF is simple:

            LLF=(LLD)(LDD)(BF)

LLD=Lamp Lumen Depreciation.  LLD is determined by dividing mean, or average, lamp lumens by the initial lumen value.

            For example:

            A standard 400W metal halide lamp provides 36,000 initial lumens

            and 24,000 mean lumens.  Dividing 24,000 by 36,000 gives us a value

            of .67 as the Lamp Lumen Depreciation factor.

LDD=Luminaire Dirt Depreciation.  LDD is a factor relating to how dirty an environment is, and how much it affects the performance of a luminaire.

The process for determining the LDD is defined by IES, and can be complicated and subjective.  We suggest you consider using one of the following categories for your calculations.

            Clean Areas (Offices, schools, retail, houses of worship, etc.) = .94

            Medium Areas (Warehouses, light manufacturing, etc.) = .90

            Dirty Areas (Machine shops, heavy manufacturing, etc.) = .85

BF=Ballast Factor.  You will find this in our literature and in ballast catalogs.  All luminaires with ballasts are influenced by this factor.  It must be considered to obtain accurate results.  Since you may not have this data at your fingertips, we suggest the following:

            All HID ballasts = 1.00

            All incandescent products = 1.00

            32W T8 fluorescent with standard electronic ballasts = .88

            32W T8 fluorescent with high ballast factor ballasts = 1.15 to 1.20

            54W T5HO fluorescent with electronic ballasts = 1.00

            Compact fluorescent with electronic ballasts = .88 to .95

So, to continue our example of the 400W metal halide, we now add the effect of the LDD and BF to determine our total LLF (Light Loss Factor).

We already have a LLD of .67.  Our project is a warehouse, so we are going to use a LLD of .90 in our layout.  HID has a ballast factor of 1.00, so we will determine our total LLF as:

            .67(LLD) X .90(LDD) X 1.00(BF) = .60(LLF)

This process is the same, no matter what the lamp, application and ballast.  The final value may change, but the same elements are used time after time.