max lenght of radial and ring for sockets?

[binky]

Maybe the wording there, mate; but you "appear" to call volt drop Zs ??I don`t think anyone suggested there was a maximum number of sockets; just a floor area.

Just to clarify: The Zs is the earth fault loop impedance; NOT the volt drop.

Sorry Binky

KME

No I'm not calling volt drop Zs so ner . If you comply with volt drop, earth loop impedence for circuit is met which is what I was getting at albeit not clearly.

 

[binky]

Max number of sockets was in 16th regs, as in upto certain floor area an unlimited number of sockets allowed, though never saw a figure stating a max number of sockets over certain floor area. Not seen any such numbers in 17th regs either.

 

[kme]

No I'm not calling volt drop Zs so ner . If you comply with volt drop, earth loop impedence for circuit is met which is what I was getting at albeit not clearly.

Sorry mate, but that is incorrect.

volt drop measures the resistances of the particular conductor size, over a given length, for a given current travelling through it.

i.e. the resistance of the neutral and phase conductors (on a single phase system).

The earth loop, (Zs, as you mentioned), is the resistance measurement of:

The phase conductor to the CU.

Supply phase to the transformer

Transformer resistance.

(TN-S) - Cable sheath back to MET.

(TN-C-S) - Supply PEN to HED

(TT) Transformer earth spike, general mass of earth, earth rod.

Earthing conductor.

CPC to point of test.

You CANNOT guarantee a circuit will pass max Zs by measuring the resistance of the phase and neutral cores of the final circuit!

or am I going totally loopy????

 

[Apache]

or am I going totally loopy????

Thought we was talking about radials...............

 

[professional]

I need to know urgently, as I`ve spent 20+ years being wrong.

...and I thought I`D set myself up for a kicking. :^O

 

[kme]

Thought we was talking about radials...............

And you can go play with an udder one! X(

It`s easy to go off people around here!!!!!!!!! ]

 

[kme]

well - if you want -

Go stand behind apache, and feel the udders. I think he`ll sort you out!!

 

[Apache]

And you can go play with an udder one! X(

Was only trying to squeeze a chuckle out

You know you love it, your sig says so

 

[Apache]

well - if you want - Go stand behind apache, and feel the udders. I think he`ll sort you out!!

I think we need a sit down and a talk. He's don't have udders. ]

 

[kme]

Applaud Smiley:^O:^O

PMS@Apache

 

[moonpig]

I went to bed 1.15 and still missed all the fun! they're talking about moonpig. Great username, good birthday cards too.............

Apache me old mukka i know we have been down this route before (and you knocked me back :^O ), but i think i love you:x:x:^O:^O:^O.

There we are i have said it, its out there :^O :^O

 

[Apache]

Apache me old mukka i know we have been down this route before (and you knocked me back :^O ), but i think i love you:x:x:^O:^O:^O.There we are i have said it, its out there :^O :^O

I do worry about you moonpig!

Pig and cow - starting a farmyard down here

 

[binky]

Sorry mate, but that is incorrect.volt drop measures the resistances of the particular conductor size, over a given length, for a given current travelling through it

You CANNOT guarantee a circuit will pass max Zs by measuring the resistance

resistance causes volt drop, ergo if resistance is good then circuit should be OK, but as you say does not guarantee overall Zs which is dependant on other factors aswell- flipping helps though :^O

 

[Dal Roberts]

on a maximum Zs note , i use 182 on site guide

for 20 a typeB 60898 is 19.51ohm(resistance per metre twin and earth) x 50 (metres) x1.2 (fully loaded temperature factor) % 1000 = 1.17ohms

,,, the maximum Zs for 20a breaker is 1.84ohms , as for the ring circuit heres how i would calculate using resistance per mm of conductor, so r1 rn the same equation i would use say at 50 metres again would be 2.5mm conductor is 7.41 ohms cpc 12.1--- same formula 50 x 7.41x1.2%1000= 0.44ohms  so r1 and rn % 4 = 0.22 ohms now the cpc 50 x 12.1 x1.2%1000= .72ohms , add r1 r2 so thats .44+.72%4 = 0.29 ohms 

so i hope this explains the difference in rings and radials 1.17 ohms radial and .29 ohms ring! same cable , same length , different result ! its time for a beer now ! that temperature factor is now 2.4 instead of 1.2 ; O)