R1+r2

[Deleted member 26818]

Your end to end testing (r1+r2), will prove that you have continuity of conductors, indicate whether there are parallel earth paths, give an indication of the CSA of the conductors and indicate if there are any high resistances in any of the conductors (perhaps a poorly terminated connection, or damage to one of the conductors).
It will also give you a value to compare your measurements (R1+R2) at each accessory.
i.e. your mesurements at each accessory should be approximately 1/4 of your end to end measurment.
The measurements at each accessory should be the same, at least within 0.05Ω of each other.
Any signifigant variations will indicate either a problem, such as a bridge accross the ring, that perhaps the accessory itself is providing a high resistance, or that the accessory is a spur.

 

[needasparks]

I see tel's woken up. Probably not the best analogy for it but works in my head. lol

 

[netblindpaul]

Can we please ensure that we use the correct R1, R2, r1 & r2 as it is easy to confuse learners and this seems to be rife.
r1, & r2 along with rn are ONLY referred to ring final circuit tests.

Also please note it is difficult to put subscripts into forum posts, all of these numbers should be subscripted to differentiate them along with the n in rn.
This would be essential in a written exam, a PIR report, or any other engineering report as these are the terms as described in the relevant BS.

 

[robsparky1975]

I would recommend you purchase a copy of guidance note 3,if your doing testing or learning then this is a must and about £25 off amazon.

 

[robsparky1975]

As said for the op,r1,rn,r2 for ring final circuits,if not a ring circuit then R1 + R2 OR other method R2 on its own(wander lead method,try to make this stick in your mind.

 

[Cj24]

r1 end to end add your rn end then divide by 4 am I right to think this will give you your r1+r2 result as in this is the kinda result I will get at sockets

 

[GaryM]

(r1+r2)/4 = R1+R2

 

[Cj24]

Sorry to ask what prob seems to be stupid questions but what's the difference between r1+r2 and R1+R2

 

[GaryM]

r1 - line conductor end to end resistance
r2 - CPC end to end resistance
rn - neutral conductor end to end resistance

R1+R2 - (r1+r2)/4

 

[telectrix]

or to simplify. R1 +R2 is the reading you get when you connect L an E at the CU and measure continuity at a socket/light on a radial. ( for a ring, you cross connect L/E, ).

 

[Cj24]

Right so think I gettin it, r1+r2 is your phase end to end add CPC end to end then if u divide that by 4 it will give you your R1+R2 which you also get this result at socket outlets

 

[telectrix]

close. you divide by 4 because on a RFC you have 2 legs ( cables in parallel ) so divide by 2, also your R1+R2 is measured mid-point , so you divide by 2 again.

 

[DaveyD]

Yes, here is an example on 2.5/1.5

r1= 0.60
r2= 1.04
rn= 0.61

r1+r2/4 Would give you your expected readings of 0.41 when you cross connect the RFC

r1+r2 = 1.64 / 4 = 0.41

The same for r1+rn/4 is 121 / 4 you are looking for a R1+RN of 0.30

HTH

 

[telectrix]

well put, that man.

 

[telectrix]

and bear in mind, there is no such thing as r1,r2,rN on a radial circuit.