Ring main Figure of 8.....

[BillyTheBandit]

Hi there wonder if anyone can help.....

ive tested continuity on a new ring main circuit I installed
the end to end were -
R1:0.28
Rn:0.28
R2:0.40
seems ok

The figure of 8 results I expect from that would be
L/N = 0.14 & L/E = 0.17 roughly

Although on some of the sockets the figure of 8 results were substantially higher then expected e.g 0.60

Why would I be receiving these results?

Thanks in advance

 

[Darkwood]

Welcome to the forum BillyTheBandit

 

[davesparks]

Did you test both sides of twin sockets?

 

[telectrix]

if you're testing the R1+R2 with a plug-in, could be contact and switch resistances of the sockets. and... did you null your meter for these readings?

 

[Octopus]

Could simply be dirty sockets - if you get "odd" readings, put the tester in and out of the sockets a few times.

 

[BillyTheBandit]

Hi thanks for the responses.

8 of the 9 sockets are single outlets, 6 of them are in a row i.e immediately next to each other one of the middle one had a v high reading 0.74 so I changed that outlet, retested and recorded a result of 0.40, still seems high...

Yes i nulled leads, I used a plug in tester and a plug in tester with connected leads as supplied with my megger 1710

On the other side of the room there's 2 singles and a double outlet, the results came back 0.17 ... So ok

The row of 6 singles is giving bizarre readings, could it be that they're immediately next to each other? Seems odd?

 

[BillyTheBandit]

They're brand new sockets

 

[davesparks]

It will most likely be contact resistance, put the plug in and out a few times and then take a measurement

 

[SJD]

There is always the possibility the circuit is not wired as a straighforward ring.

For example, last week, I found one with higher than expected readings on a few sockets - turned out the circuit was wired as a figure of eight, one large loop and one small loop for these sockets. In this case with a FCU up in the loft connecting the two loops together, put there is would seem to get round high Zs readings on these sockets, they are protected by the 13A fuse (that nobody would have easily found, as it was up in the loft!).

In summary, if there are a set of suspicious readings, perhaps there is some suspicious wiring.

 

[Sintra]

Did you connect the figure of 8 up correctly. Ie L of cable 1 to cpc of cable 2 and cpc of cable 1 to L of cable 2.

 

[Jay Sparks]

They could all be spurs from the two sockets at the other side of the room??!!
Just a thought.

Jay

 

[Sintra]

The op stated he installed the circuit so he should know how it is wired

 

[Jay Sparks]

The op stated he installed the circuit so he should know how it is wired

Ahh, good point. I didn't really read the full post.lol I'm half way through a bottle of Pinot Noir and my little girl is crying, so I am skim reading..lol

Jay

 

[BillyTheBandit]

Yes sintra all tests were carried out correctly and I'm sure it was wired in 1 loop! I will test again tomorrow the meter was jumping in readings sporadically so could be that. Haha Jay that would make the most sense!

 

[Octopus]

Cheap crxp sockets from a shed is my guess

 

[Jay Sparks]

Yes sintra all tests were carried out correctly and I'm sure it was wired in 1 loop! I will test again tomorrow the meter was jumping in readings sporadically so could be that. Haha Jay that would make the most sense!

Sometimes the leads from your MFT can give dodgy readings. Try using croc clips on the actual cables of the actual sockets. If you hold them tight, they will give a better, more accurate reading. At least this would tell you if it was the sockets themselves!

Jay.

 

[tony mc]

Make sure your batteries in your tester are not on there way out my resistance readings always start playing up when they need changing !!

 

[Octopus]

Make sure your batteries in your tester are not on there way out my resistance readings always start playing up when they need changing !!

Or if its a Metrel your leads need replacing!

 

[Simonslimline]

As has been said, unscrew the sockets and test on the actual terminals rather than using the plug in lead. Hopefully it's just down to the contacts on these sockets.

 

[Risteard]

Sometimes the leads from your MFT can give dodgy readings. Try using croc clips on the actual cables of the actual sockets. If you hold them tight, they will give a better, more accurate reading. At least this would tell you if it was the sockets themselves!

Jay.

If you were to disconnect and reconnect the conductors to catch them under a crocodile clip, however, this would somewhat mitigate the value and reliability of testing as you may subsequently introduce a fault!