Lower r2 end to end reading than r1 & rn

[TJC1]

Hi peeps. Doing an end to end test on a ring final circuit.
R1- 0.43
RN- 0.44
R2- 0.33

Its old stranded 2.5, seems to have about 7 stands on the live n neutral conductors, and about 4 strands on the cpc conductor.

Why is the r2 lower than the r1 & rn!!

HELP

 

[yellowvanman]

Parallel paths probably!

 

[Simonslimline]

parallel path possibly.

 

[Simonslimline]

Parallel paths probably!

Got there just before me.

 

[Guest77]

Hi peeps. Doing an end to end test on a ring final circuit.
R1- 0.43
RN- 0.44
R2- 0.33

Its old stranded 2.5, seems to have about 7 stands on the live n neutral conductors, and about 4 strands on the cpc conductor.

Why is the r2 lower than the r1 & rn!!

HELP

Well you had had one answer, but I wonder do you have an opinion why?

 

[Lucien Nunes]

old stranded 2.5

Not likely, expect it to be 7/.029 which normally has 3/.029 CPC. SO when you calculate what you expect R2 to be, remember the ratio of resistance per metre will be would be 7:3 not 2.5:1 or 5:3. IIRC there has also been 7/.029 with 3/.036 CPC.

about 4 strands on the cpc

4 ?! Are the numbers 1, 3, 7, 19, 37 familiar at all?

 

[Pete999]

Hi peeps. Doing an end to end test on a ring final circuit.
R1- 0.43
RN- 0.44
R2- 0.33

Its old stranded 2.5, seems to have about 7 stands on the live n neutral conductors, and about 4 strands on the cpc conductor.

Why is the r2 lower than the r1 & rn!!

HELP

Same as post 5,4,3 and 2

 

[TJC1]

Surley parellal paths wont be a factor when disconnected from the earth bar?

 

[yellowvanman]

Surley parellal paths wont be a factor when disconnected from the earth bar?

Could be!

eg. you have 5A lighting sockets and ring main sockets fixed together. So if the metal back boxes are earthed by their respective cpcs, from one position to the next will be 2 cpcs in parallel.

You could also measure r1, rn and r2 at a socket location, and you might get different measurments because of the measurement position in respect to the parallel paths involved.

 

[SJD]

Surley parellal paths wont be a factor when disconnected from the earth bar?

For example, if you have more than one item of equipment on the circuit with a connection to water/gas pipes, then you may have a parallel path that is very low resistance. For example a gas boiler, a gas hob with electric ignition, etc.