Calculations: Floodlighting & Mounting Height
Use the following formula to calculate floodlighting and mounting height depending on lamp type and wattage.
| Mounting Height Guide |
| Watts |
H.P. Sodium |
Metal Halide |
Mercury Vapor |
Tungsten Halogen |
| 70 |
10-15' |
|
|
|
| 100 |
15-20' |
|
|
|
| 150 |
20-25' |
|
|
|
| 175 |
|
|
18-23' |
|
| 200 |
20-25' |
|
|
|
| 250 |
22-27' |
20-25' |
20-25' |
|
| 400 |
30-35' |
25-30' |
20-25' |
|
| 500 |
|
|
|
15-20' |
| 1000 |
40-50' |
40-45' |
35-40' |
20-25' |
| 1500 |
|
|
|
25-30' |
| Light Depreciation Chart (Cleaning every 3 years) Environment |
| Clean |
Medium |
Dirty |
| .96 |
1.01 |
1.06 |
Step 1: Determine foot-candle level from outdoor candle table below.
Step 2: Determine square footage of area to be lighted (length x width).
Step 3: Determine type of fixture to be used and proper mounting height.
Step 4: Identify initial lumens of fixture type (sese product description)
Step 5: Determine dirt depreciation factor of fixture from Light Depreciation Chart below.
Step 6: Use this data in the formula below to calculate the number of fixtures.
- Light Fixtures Formula:
Number of fixtures = 3 x the number of footcandles needed x the square footage of the area divided by the initial lumens of the fixture
(lamp) type x dirt depreciation.
- Example:
Using 400 watt hps on 30' pole. 3 x 2 x 40,000 divided by 50,000 x 1.01 = 4.85. (Final fraction should be rounded up.) Required number
of fixtures = 5.
- Note: This guide is meant to help in making lighting estimations, not precise calculations.