Published:
21 February 2012
Category:
Q&A
Anthony Speight asks how to calculate the voltage drop on a planned electrical ring circuit. His question has been answered by the NICEIC (Theme – Installation Tips):
This Q & A is one of thousands posted in our Technical Expertise area, and answered on a daily basis by our Voltimum Experts.
Question: How do I calculate the voltage drop on a proposed 4mm cross-sectional area ring circuit of 100m in length? I need to do this at the design stage.
Answer: Adapted from the IET Design Guide page 15 - the answer, I figure, is 8.8V.
This can be calculated as follows: Vd = L x Ib x (mV/A/M)/ 4 x 1000.
Where:
L = length of cable run
Vd = voltage drop
Ib = design current
(mV/A/m)= voltage drop/ampere/metre - from BS7671:2008, Appendix 4.
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