vd and ccc for rings

[linnsound]

hi there ..when working out current carrying capacity for ring I found with correction factors the current rating to be 43A, and the tabulated rating to be 27A..now am i right in thinking that as it is a ring the circuit can be treated as two halfs, ie permissible to have 54A( 27A per half of the ring)? does the same also stand true for Voltage drop calculations?

linnsound

 

[Spark123]

The regs call for each leg of the ring to be able to carry 20A (2.5mm² minimum for twin and earth).
As for volt drop, this is complicated by the fact that not all of the current is used at the mid point and the loading isn't fixed. The conventional circuits given in the OSG I believe to be calculated somewhere between the max efli and the volt drop at mid point.

 

[linnsound]

thanks spark123

I was taking the 27A a side from table4D1A..method 1. Are you referring to method 4?
I am confused by vd on rings as a result of the standard circuit tables..which state 32A type B max run (tn-c-s)84m.

If i then caculate vd by {(vd/A/m)*Ib*L}/1000

ie {18*32*84}/1000 = 48.34V....even were the calc to be halfed this far exceeds 9.2V....were i to transpose the cacl for max cable run.

L={maxVD * 1000}/L*Ib
={9.2*1000}/18*32 = 16m. Double for ring run =32


what are your thoughts m8