Examples of calculation
All the values stated in the columns in table 1 - Sky type refer to a situation of 1 metre rigid tunnel with 1 elbow.
As for calculation of the light transmission in other situations, the following rules apply:

  • Reduction of light transmission per metre tunnel = 6%
  • Reduction of light transmission per elbow = 10%

See the examples of calculation below - all examples are based on a sunny summer.

Example 1
Lumen output for installation situation with 1 elbow + 1 metre rigid tunnel = 6500 lumen

 

A: Elbow joint
B: 1m rigid tunnel

Example 2
Lumen output for installation situation with 1 elbow + 3 metres rigid tunnel = 5743 lumen (6500 x 0.94 x 0.94)

 

(The figure 6500 is lumen output from example 1, with 1 elbow and 1 metre rigid tunnel)
(Transmission 1 metre tunnel = 0.94)

 

A: Elbow joint
B: 3m rigid tunnel

Example 3
Lumen output for installation situation with 2 elbows + 3 metres rigid tunnel = 5169 lumen (6500 x 0.9 x 0.94 x 0.94)

 

(The figure 6500 is lumen output from example 1, with 1 elbow and 1 metre rigid tunnel)
(Transmission 1 elbow = 0.9)
(Transmission 1 metre tunnel = 0.94)

 

A: Elbow joint
B: 3m rigid tunnel

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