Volt Drop in Ring Circuits

[Trip Hazard]

Can anyone enlighten me on how to work out Volt Drop on a ring circuit?

 

[Andy™]

mv/a/m / 1000

get your design current, volt drop for the cable you plan to use, and length, and your almost there

 

[Trip Hazard]

Yes i've done all that - was just wondering how it differs from a radial circuit

 

[Zeespark]

The only way V.D. will affect any circuit is due to length, load. etc. Doesnt matter if it is a ring final or a radial circuit.

AndyGuiness Drink

 

[oneofthedamned]

Page 44 OSG Table7.1 gives cable size, and max length for different protective devices and types of circuits. Useful book if you don't already have it.

 

[PoorFish]

Greetings folks

can some one tell me what all the abbreviations mean??

mv = milli Volts

A=area m = metre

1000 = ?

Thanks

P

 

[Andy™]

Greetings folkscan some one tell me what all the abbreviations mean??

mv = milli Volts

A=area m = metre

1000 = ?

Thanks

P

mV = milli volts

A - amps (Any idea why this isnt I?)

M - metre

1000 is to convert mV into V

 

[PoorFish]

Thanks for the ultra speedy reply

All the best

Pat

 

[SPECIAL LOCATION]

Can anyone enlighten me on how to work out Volt Drop on a ring circuit?

Hello Trip!

we know max Volt drop = 3% lights 5% other circuits!

so 11.5v for socket circuits..

Lets chuck a few numbers around..

First.. lets consider a radial circuit

20amps

2.5mm

30 meters long

from OSG pg 133 table 6E2:- 2.5mm, volt drop = 18mz/amp/meter

Assume circuit running full wack!

so volt drop = (18mv * 20 * 30)/1000 = 10.8v ok!

Now lets assume two identical radial crvuits...

joined together at furthest point.... is a 60m ring circuit,

but cuz two parallel identical paths, Resistance is halved

& volt drop halved...

i.e would be equivalent to 18x20x15/1000 = 5.4v

or ( 18x20x60/1000 ) /2 = 5.4v

but remember its a bit more tricky with an existing ring circuit with branches and spurs off!

 

[PoorFish]

does it make any difference if its armoured cable

also is there a specific place in the OSG in relation to armoured or is it irrelavant when working out volt drop.

I have just bought the OSG and am still getting to grips with it but cannot seem to find any specific info on armoured cable

cheers

p

 

[Andy™]

does it make any difference if its armoured cable also is there a specific place in the OSG in relation to armoured or is it irrelavant when working out volt drop.

I have just bought the OSG and am still getting to grips with it but cannot seem to find any specific info on armoured cable

cheers

p

the volt drop is different, check the tables in 7671. the rest of the formula is the same

 

[PoorFish]

thanks for that

will have to wait till im back to college for that

have not taken the plunge on the that baby yet

regards

P