R1, Rn and R2 readings - some advice please.

[chrisgc]

I have just practised on my circuit at home.

Was doing the ring continuity test and had the following results:

R1 = 0.49
Rn = 0.50
R2 = 0.99

(as per step 1 in the OSG).

As it states the r2 reading should be proportionately higher than that of the line and neutral loops - is the above acceptable?

It is old wiring colour on the ring and the csa of the protective conductor seems only slightly smaller than the line and neutral, which is approx 1.5mm.

OSG states the 1.67 x rule which would indicate in ideal scenario the R2 reading should be approx 0.83.

Any advice would be appreciated.

 

[telectrix]

your R2 seems a little high to me. make sure your croc connections are clean and tight on the conductor. a slightly loose connection in a fitting could also be the culprit

 

[chrisgc]

I was thinking about possibly checking the terminals for any loose connections at the back of each of the sockets - so will do that and see what happens.

 

[BlueToBits]

There is quite a lot of late 70's - early 80's 2.5mm T&E with 1mm ECC, it could however be due to one or more of several possible reasons. You could check each connection but The result is not un-typical, and I personally wouldn't cite it as a defect, or spend my customers cash in time trying to improve it. If the circuit is RCD protected it only requires a Zs of less than 1667 ohms in any event. If it isn't then, in my book, you would probably be offering a better service to your customer by fitting one rather than to try to locate the cause. It's one of those occasions you have to use your experience and gut judgement on, taking other factors the installation may reveal into account.

 

[telectrix]

is it a socket circuit, or lighting?

 

[m4tty]

think it's a ring mate

 

[chrisgc]

is it a socket circuit, or lighting?

It''s a Ring. Downstairs lounge/diner and upstairs bedrooms.

 

[Sparky Ninja]

So it's the r1, r2 & rn you have measured (lower case).

It's very common for the r2 reading to differ from the x1.67 theory when testing an existing installation. Most often it would be lower due to the parallel paths however it can on occasion be higher according to cable csa or even simple connection methods. I myself wouldn't worry about the readings you've obtained.
But if you want to investigate further then it's all good practice.

 

[ezzzekiel]

agree with widdler readings can vary and will rarely read exactly what you expect, providing they are pretty much as you would expect then i wouldnt worry