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View Full Version : Voltage Drop in Lighting Circuits


koemae
Jan 13, 2009, 10:30 AM
When figuring the voltage drop in a branch circuit with multible light fixtures.

I can size my load (11.5 amp) & voltage drop (2.14%) to the first fixture based on a 277v (271.08v) circuit with the total length (130') of the circuit.

When I proceed on to the next fixture how is that handled?

Do I need to reduce the 277-volts to the next fixture based on the calculations in my homerun back to the panel ( 271.08) and keep reducing the voltage based on each calculation until I reach the end of the circuit?
Or is it to remain 277v through-out the calculation and I just add each voltage drop % to the home run calculation (2.14%) to get my total voltage drop % to the end of the circuit.

sarnian
Feb 7, 2009, 04:40 AM
Please explain your precise problem once more.
Of course the voltage drop increases towards the common feeding point, as there the current is greater.
If you keep within 5 % of the supply voltage, that is never considered a problem.
If you need a detailed solution, you should provide detailed information, i.e. a wiring diagram with all lights involved, quantities, power consumption, cable diameters used, etc.