Pittsburgh Business Daily

How to add up different insulation resistance values to get the overall resistance value?

If the insulation resistance values of 5 diffrent circuits are 200M ohm, 500M ohm, 300M ohm, 400M ohm and 250M ohm. How do u work out the overall resistance of the installation. (Wat is the formula to use) THANKS

Public Comments

1. If the resistances are in series add them. R=R1+R2+R3+R4+R5 If the resistances are parallel, then add their reciprocals. 1/R=1/R1+1/R2+1/R3+1/R4+1/R5
2. it depends that how they are connected if they are in parallel then the formula is: 1/r = 1/p + 1/q + 1/r ........... (r is the total resistance and p,q,r are individual resistance eg: 1/r = 1/200 +1/500 + 1/300 +1/400 + 1/250 1/r = 101/6000 r = 6000/101 ohm but if the resistances are in series then we use: r = p + q + r ...... eg: r = 1650 ohm if the resistances are connected in parallel then the total resistance is always less than the individual resistances but in the other case the individual resistance is always less than the total resistance.
3. Parallel : 1/R(Total) = 1/ R1 + 1/R2 + 1/R3 NOTE : The total resistance will be less than the smallest individual resistor. Series: R(Total) = R1 + R2 + R3 NOTE: The total resistance will be greater than the largest individual resistor.