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the magic 1667 ohms
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<blockquote data-quote="Nicky Tesla" data-source="post: 22760" data-attributes="member: 445"><p>I = V/R, R = V/R, 50v (max touch voltage)/0.03 (30mA) = 1666.6 ohms</p><p></p><p>the fact that we have moved from 240v to 230v does not make a difference here, cos max touch voltage is still 50v.</p><p></p><p>If there is a fault to earth on a piece of equipment, the voltage on that equipment will RISE from the original 0v upwards (this will take only fractions of a second). When this voltage has risen to 50v, if the resistance to earth on r2 is low enough, then at least 30mA will flow to earth and the RCD will trip in time. The voltage may rise still further than 50v but only due to the time it takes for the RCD to work.</p></blockquote><p></p>
[QUOTE="Nicky Tesla, post: 22760, member: 445"] I = V/R, R = V/R, 50v (max touch voltage)/0.03 (30mA) = 1666.6 ohms the fact that we have moved from 240v to 230v does not make a difference here, cos max touch voltage is still 50v. If there is a fault to earth on a piece of equipment, the voltage on that equipment will RISE from the original 0v upwards (this will take only fractions of a second). When this voltage has risen to 50v, if the resistance to earth on r2 is low enough, then at least 30mA will flow to earth and the RCD will trip in time. The voltage may rise still further than 50v but only due to the time it takes for the RCD to work. [/QUOTE]
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the magic 1667 ohms
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