r1+r2 testing

[james king]

hi all just reading up on continuity testing (r1+r2 test) say i have a ring main of 40m long serving 10 sockets..

the reading i have got is say 0.35ohms

but on 1 socket i have a higher reading of 0.46ohms

now i have learnt at collage this may be caused due to a loose connection

could this also be due to a spur?

are spur readings usally higher

 

[Sparky Ninja]

Can be caused by a spur. You are referring to R1&R2, not r1&r2, right?

 

[james king]

yep i am sorry

 

[Sparky Ninja]

High R1&R2 readings can result from loose connections, however the r1, rn & r2 tests would normally be done prior, and in doing this, the loose connections will become apparent. The most common example for high R1&R2 readings used in syllabus is a spur, or 'ring within a ring' arrangement. I am surprised that loose connections was used as an example.

 

[james king]

Can u give me some examples of what reading u would expect if you were to plug in ur tester to a spur please sorry about caps

 

[Deleted member 9648]

The R1R2 reading of a ring with a spur will be the R1R2 of the ring ,plus the R1R2 of the cable between the point of connection to the ring and the socket served by the spur.

 

[james king]

please can u expand on ring within a ring?

 

[james king]

i understand that cheers thanks for tht

 

[ezzzekiel]

please can u expand on ring within a ring?

a ring within a ring is pretty much what it says where a second ring has been added to the original, in itself this is not a problem unless the ring gets broken somewhere then you will have a ring with a radial attached when testing you would find all sockets on the ring read as they should but the radial readings will increase as you move outward

 

[IQ Electrical]

Can u give me some examples of what reading u would expect if you were to plug in ur tester to a spur please sorry about caps

Say the R1+R2 reading for the socket you're testing at is 0.35 Ohms and a spur has been taken from this point, say 10 metres of 2.5/1.5 pvc/pvc cable then your R1+R2 at the spur will be approximately 0.45 Ohms (allowing 0.10 Ohms for the spurred length of cable).

When this value (assuming it is the highest on the circuit) is added to the Ze or Zdb, you have the Zs for the final circuit.

 

[millwall ken]

High R1&R2 readings can result from loose connections, however the r1, rn & r2 tests would normally be done prior, and in doing this, the loose connections will become apparent. The most common example for high R1&R2 readings used in syllabus is a spur, or 'ring within a ring' arrangement. I am surprised that loose connections was used as an example.

It annoys me too, that a loose connection is generally used as an example for high readings, when it could be a multitude of sins causing it - However I believe that they use that example as it is the most common cause.

 

[telectrix]

Say the R1+R2 reading for the socket you're testing at is 0.35 Ohms and a spur has been taken from this point, say 10 metres of 2.5/1.5 pvc/pvc cable then your R1+R2 at the spur will be approximately 0.45 Ohms (allowing 0.10 Ohms for the spurred length of cable).

When this value (assuming it is the highest on the circuit) is added to the Ze or Zdb, you have the Zs for the final circuit.

nice and clearly put, IQ.