A
Alessandro
Edited: sorry of course Ze should be added to the post below, Table 41.3 is for comparing Zs.
Hi, it is my understanding that Table 41.3 of BS 7671 should be used for comparing the tabulated values with the resistances of:
1) the line conductor at 70 degC;
2) cpc at initial temperature, as given in Tables 54.2 to 54.5.
This is what note 2 under Table 41.3 says.
This means that I should apply a factor of 1.2 to the measured value of R1 if ambient temperature is 20 degC, or simply add 2% for every 5 degrees of difference between initial temperature and maximum operating temperature. Then add the measured value of R2, and apply factor only if necessary (if initial temperature is different from ambient temperature).
But if I measure R1 + R2 directly, then I can't apply a single factor to the obtained value. Am I correct? Then I should simply obtain the values of R1 and R2 separately, or by subtraction from Rn + R2, then apply the factor for R1 to R1, and the factor for R2 to R2. In short:
Ze + R1 * c1 + R2 * c2 < corresponding value in Table 41.3.
But I couldn't find this procedure anywhere. Am I misinterpreting the Regs? What should I do?
Hi, it is my understanding that Table 41.3 of BS 7671 should be used for comparing the tabulated values with the resistances of:
1) the line conductor at 70 degC;
2) cpc at initial temperature, as given in Tables 54.2 to 54.5.
This is what note 2 under Table 41.3 says.
This means that I should apply a factor of 1.2 to the measured value of R1 if ambient temperature is 20 degC, or simply add 2% for every 5 degrees of difference between initial temperature and maximum operating temperature. Then add the measured value of R2, and apply factor only if necessary (if initial temperature is different from ambient temperature).
But if I measure R1 + R2 directly, then I can't apply a single factor to the obtained value. Am I correct? Then I should simply obtain the values of R1 and R2 separately, or by subtraction from Rn + R2, then apply the factor for R1 to R1, and the factor for R2 to R2. In short:
Ze + R1 * c1 + R2 * c2 < corresponding value in Table 41.3.
But I couldn't find this procedure anywhere. Am I misinterpreting the Regs? What should I do?
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