length of cable runs

[i=p/u]

is this correct for lighting circuit of 1.5mm line and 1mm cpc
ze+R1+R2=zs

b6 mcb ze R1+R2
6.18ohms - 0.8ohms =5.38ohms


cable per meter = 0.03020ohms so 5.38ohms/0.03020=178.1M

does this mean my lighting circuit can be this length 178M and still be within zs value... cheeers if makes sense

 

[IQ Electrical]

In this instance i=p/u is correct,

Ze+R1+R2=Zs

I think Telectrix commented before the edit...

 

[i=p/u]

ok loads to consider, so if you were wiring lighting circuit 5A, what is the sums you guys would do to dertamine how many rooms you could do?

isit say 4 rooms down stairs lighting circuit.
living room 10 spotlights 50W =500W
hall 1 pendant 60W
kitchen 8 spotlights 50W=400W
utility room i 2 pendants 60W=120W

1080W/230v= 4.7A ib=4.7A
in=6A
it= in/ca 1,ci 1,cg 1,cc 1
it=6a so would use obv 1.5 t&e
then vd is 19 x ib x L

so heres where im wondering what lenth of cable i can use on 1 circuit, do i have to physicaly measure what i need?? hense knowing the length.and does the switch drops add on to this? thanks if im annoying you and you still trying to get through

 

[Chr!s]

so when you designing a lighting circuit , how do you approach it? ive seen page 45 in the osg would give you 90 meters would this include switch drops aswell???

it says in osg pg 44 5amp on 1.5mm/1mm would go 71m , and i think vd is included

ok loads to consider, so if you were wiring lighting circuit 5A, what is the sums you guys would do to dertamine how many rooms you could do?

isit say 4 rooms down stairs lighting circuit.
living room 10 spotlights 50W =500W
hall 1 pendant 60W
kitchen 8 spotlights 50W=400W
utility room i 2 pendants 60W=120W

1080W/230v= 4.7A ib=4.7A
in=6A
it= in/ca 1,ci 1,cg 1,cc 1
it=6a so would use obv 1.5 t&e
then vd is 19 x ib x L

so heres where im wondering what lenth of cable i can use on 1 circuit, do i have to physicaly measure what i need?? hense knowing the length.and does the switch drops add on to this? thanks if im annoying you and you still trying to get through

The reason why theres a difference between yours and those in the onsite guide is that your calculations are based on all the load at the extremity of the circuit.

Say on your radial(lighting) you have max length based on the load at the extremity, if you evenly distribute the load you can in effect double the max length.

I used a Ct value of 1 just as an example, which errs on the side of safety when in actual fact Ct will be more than one due to the CCC of 1.5mm T+E and the fact you would be limiting it to a max of 5A when it is capable of carrying more.

The Ct will be less than 1 if Ib is less than It.

Also it is impossible to say what the ambient temperature of the area surrounding the cable will be........is it in an attic, under insulation etc etc, the OSG bases it's values on ideal situations but does make you aware in the notes associated to the particular table.

It lists the various ref methods and the ambient required for compliance.

 

[i=p/u]

so could someone show me a clear workings out of a typical downstairs lighting circuit.. il send you fiver in pos or just be greatfull of your knowledge?

 

[i=p/u]

i know one of you can put me right

 

[Guest 004]

Indeed it will

 

[Guest123]

It lists the various ref methods and the ambient required for compliance.

Yes it does, I meant in a certain scenario such as i/pu has described where I am not present, how on earth could I tell which factor needed applying if I couldn't see the actual cable run.

 

[i=p/u]

just pretend its 30 degrees normal ,no grouping factor, no insulation and no bs3036 fuse or in a duct
to keep it simple..

i just would like to know how you dertamine how long you can run your cables and do switch drops count aswell??

i know you can and do the sums and if your wrong, you can increase the csa

 

[andyb]

Yes i=p/u, it does include the switch drops.

 

[Guest123]

The Ct will be less than 1 if Ib is less than It.
QUOTE]

Correct, I knew what I meant!

 

[i=p/u]

well when you see as lenny above said 48m on a 5amp breaker, it doesnt seem a while lot to me? and does that count down and back up in switch drops??/???

 

[Chr!s]

Ive got no reference material so some figures may be incorrect.

Take 1.5 mm cable, CCC 20 amp method C, lets assume ref 103 so CCC= 10amp, mV/A/M = 29

MCB = 6 type B, Load = 6 amp

Ct= 0.915

So if we assume 6 amps at the extremity we get, 6.9 x 1000/ 6x (0.914x29) = 43.35.


If we assume the 6 amps is distributed along the circuit then this will increase the max length.

Ill assume a lenght of 86 meters, double the above, and break it down into 12 x 0.5 amp loads, 7.17 meters apart

The first section sees 6 amp, the next 5.5 amp next 5 and so on.

The volt drop would = 7.38 volts

So if we assume 100 watt per light and evenly distribute them you can see how you extend the lenght.

HTH

 

[i=p/u]

maybe this will make sense soon, thanks

 

[Wiredspark]

i just would like to know how you dertamine how long you can run your cables and do switch drops count aswell??

Sorry if i sound out of sorts here, but shouldnt you know this???

 

[IQ Electrical]

I believe he's currently doing 2330 L2 so these are good questions to pre-empt L3