Theatre Lighting Dimmers

[djlander]

Hello guys

got a question relating to lighting dimmers
I have been asked to install a 24 way Stage lighting dimmer and each circuit is 10A running around 50m to each socket, the cables will be housed In 100 x 100 trunking, I am just little confused at the groping factors as not every circuit will be used at the same time and what is used will be on at say 60% per circuit.

do I apply the 0.38 grouping factor as there is over 20 circuits or can It be less as only 50% to 60% of he 24 circuits will be used at any one time??

there is also probably 6 other power circuits in the trunking

Let me know what you think

 

[Lucien Nunes]

I am just little confused at the groping factors

I've never been able to get a firm grasp of them either!

The supply capacity to the dimmers might limit the total possible number of fully loaded circuits. This is always the worst case - a larger number of circuits with less load per circuit, totalling the same load, will cause less heating per unit length of trunking. Depending on venue application you may be able to apply diversity based on bar loadings and/or on specified fixture types, but for some systems that is not permissible because of the expectation that a whole block of circuits will be fully loaded. At 50m voltage drop might just start to play a part in your cable choice. Each situation is different and it requires some specialist knowledge.