How Do I Know If A R2 Reading Is Correct

[garaoke]

I got a electrical test to check ze was .18 zs was .4 for a cooker circiut of length 1m. R2 was .00 on test sheet, also a ring main of 20m r2 was .05 I thought no chance as r1+r2+ze would not work out any info guys

 

[Andy™]

R2 should be resistance per metre x length of cable installed...

if you tested Zs after an RCD, you usually get a slightly higher reading

 

[sparkytim]

Sounds like the leads were not correctly zero'd. 

 

[garaoke]

So the ring main of 20m at .05 ohms is defo wrong

So the reading of .05 for the ring main is defo wrong

 

[sparkytim]

From my calcs a 20 mtr 2.5mm R1 should be 0.15 ohms, or thereabouts and the R2 1.5mm CPC 0.25 

 

[ProDave]

From my calcs a 20 mtr 2.5mm R1 should be 0.15 ohms, or thereabouts and the R2 1.5mm CPC 0.25 

If it's a 20 M Ring final, then the end to end resistances are as you state.

But R1 and R2 will in fact be half that due to two cables in parallel (strictly speaking it will depend on where on the ring you test)

That's why the figure of 8 test was devised, that should give the same reading wherever you test on the circuit.

 

[sparkytim]

I stand corrected

what I should have more correctly stated was that the END TO END continuity readings for the L and the CPC on a 20 mtr Ring Final Circuit would be expected to be in the region of those values.

Added together and divided by four will give the expected R1 + R2 value that should be confirmed by the cross over method

(L of cable one connected with CPC of cable 2 and L of cable 2 connected with CPC of cable 1 and measure the continuity between the two )

Thanks Dave