hi was wondering what every ones opinions are regarding volt drop calculations i know there are 2 ways the ohms law way and the way where you use tables of the bs7671, the thing is i taught my self how to do volt drop calcs so i learnt the ohms law way is this a acceptable way or should i do it the bs7671 tables way like for instance this is how i would do it
a lighting circuit run in 70 degree c thermoplastic 1.5mm twin + cpc for 30 meters with 10 light pendants on the circuit so say 4 amps max
according to appendix I table I1 in the onsite guide the resistance per meter of 1.5mm copper conductor is 12.10 mOhms per meter so for r1 + rn it will be 24.20 mOhms per meter then times it by the length 30m so it is 726 mOhms then we divide by 1000 to make it to ohms so it will be 0.726 ohms then add the multiplier in table I3 for max operating temperature of 1.20 so that will be 0.8712 ohms then we can use ohms law I x R = V so 4 x 0.8712 = 3.48 volts so that would be within the max volt drop allowed on a lighting circuit (i know you can do all this in 1 calculation like so mohms x length x multiplyer divided by 1000 which will get you your total resistance then use ohms law) this is the way i taught my self how to do volt drop should i do it the other way or carry on this way?
a lighting circuit run in 70 degree c thermoplastic 1.5mm twin + cpc for 30 meters with 10 light pendants on the circuit so say 4 amps max
according to appendix I table I1 in the onsite guide the resistance per meter of 1.5mm copper conductor is 12.10 mOhms per meter so for r1 + rn it will be 24.20 mOhms per meter then times it by the length 30m so it is 726 mOhms then we divide by 1000 to make it to ohms so it will be 0.726 ohms then add the multiplier in table I3 for max operating temperature of 1.20 so that will be 0.8712 ohms then we can use ohms law I x R = V so 4 x 0.8712 = 3.48 volts so that would be within the max volt drop allowed on a lighting circuit (i know you can do all this in 1 calculation like so mohms x length x multiplyer divided by 1000 which will get you your total resistance then use ohms law) this is the way i taught my self how to do volt drop should i do it the other way or carry on this way?
