Ring Circuit Values

[comlongon]

Looking for some advice, I have tested a property and on the ring main circuits the values do not tally up using the formula

(r1 + r2) / 4 = R1+R2

Although the R1+R2 tallys up using the formula

R1+R2 = Zs - Ze



Is this an actual fault that needs recording on a periodic ? I have been told it is but i cant find a regs number to go with it


Thanks

 

[Spudnik]

The calculation method (2) cannot be relied upon to be accurate, however it is an acceptable method when doing PIR's in certain circumstances. I have done this before out of curiosity and the results and calculations i got were almost the same.

On a new installation, the measured value should be recorded as technically, the installation should not be energised until dead testing is done.

So, in other words, test it, dont calculate it if possible.

 

[trebor]

Looking for some advice, I have tested a property and on the ring main circuits the values do not tally up using the formula

(r1 + r2) / 4 = R1+R2

Although the R1+R2 tallys up using the formula

R1+R2 = Zs - Ze



Is this an actual fault that needs recording on a periodic ? I have been told it is but i cant find a regs number to go with it


Thanks

the whole idea of the ring final circuit continuity test is to find any problems with the ring ie is it a ring or are there interconnections which make it appear to be a ring on the end to end tests,if the readings are bit out on one or two s/o it could be a simple loose connection, (these wont show on the end to end if the conductors are twisted at the s/o) or if you are measuring at the tubes simply worn socket outlets, I did a test last weak where the R1 R2 readings were completely different on the two sides of a twin socket,the s/o being defective internally, if your Zs readings at each socket are much the same without any significant increases or decreases around the circuit then I wouldnt worry, if they all over the place then coupled with the continuity readings i would dig a bit deeper

The regs only quote atest is required 612.2.2, GN3 gives more specific guidance, any problem should be marked on your pir as requires further investigation

 

[super spark]

I agree with trebor,

The purpose of the test is to find faults !!!!!!!

The equation R1+R2 = Zs - Ze MUST NEVER BE USED

2 words PARALLEL PATHS... parallel paths = false readings. I cant believe anybody would even think of using that equation.

1 possible reason for your readings not matching may be due to the size of the cpc. older circuits incorporate 2.5/1 and therefore 1.67 would not apply !