r1 + r2 No Reading, Open Circuit!

[Eugene Herbst]

Hi All,

Busy doing an EICR and on 2 of the Socket Rings for the dead test I get the following results:
Step 1: End to End (0.32 ohm r1, N ) & (r2 = 0.51 ohm)
Step 2: r1 to N 35.6 ohm
Step 3: r1 to r2 no reading

At first I thought maybe I was testing the wrong r2 in/out but I traced the cable back and it matched the T&E so it's definitely matched & crossed correctly.
Also before I isolate the board I always check the sockets with my Kewtech "socket & see" device, which is normally pretty accurate, and this didn't flag any issues!

Any ideas on why there is no r1 + r2 reading and why r1 + N is off the charts?

 

[Lucien Nunes]

Do you get similar readings from multiple socket outlets? If that's a specific socket, you might be seeing the effect of high-resistance contacts e.g. from corrosion.The end-end test is OK because only the continuity of cable via the terminals is involved, and the Socket-&-See indicates correctly because its very low current requirement will enable it to 'See' through many kilohms of resistance (which is why they are not a great idea) and show a connection even when it is off the scale of the continuity range of the MFT.

 

[ChrisElectrical88]

Are you sure the cables aren’t crossed over MCBs if your getting the same end to end readings on 2 circuits?

 

[Mark Wright]

You mean R1+R2 ?
little "r" is End to End.

 

[Eugene Herbst]

Do you get similar readings from multiple socket outlets? If that's a specific socket, you might be seeing the effect of high-resistance contacts e.g. from corrosion.The end-end test is OK because only the continuity of cable via the terminals is involved, and the Socket-&-See indicates correctly because its very low current requirement will enable it to 'See' through many kilohms of resistance (which is why they are not a great idea) and show a connection even when it is off the scale of the continuity range of the MFT.

It's a fairly new installation, less than a year! The whole circuit shows the same readings at each socket, and when opening up all of the conductors are seated fine which is why i'm puzzled.
The socket & see helps me decide my sample size, and to be fair has found reverse polarity / broken earth on a few occasions, but I still check polarity with the MFT at all the sockets!
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Are you sure the cables aren’t crossed over MCBs if your getting the same end to end readings on 2 circuits?

Cables are matched and not crossed over MCB's, double checked all of them making sure that the conductors came from the same T&E sheathing from both in/out cables and then cross connected!

 

[westward10]

Take the socket and see out if the equation, test direct to the socket terminals with your mft see if you get the same result.

 

[telectrix]

start with a wander lead. measure R1 from CU to sockets. repeat for R2.

 

[Mark Wright]

sorry to have a pop but I've seen it a few times getting r and R correct is important.

I normally find correcting things like light bulb,Lamb - Ring -Ring final etc a bit pointless but getting this correct is important.

 

[Eugene Herbst]

You mean R1+R2 ?
little "r" is End to End.

Yes, I mean R1+R2
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start with a wander lead. measure R1 from CU to sockets. repeat for R2.

Did that, 0.16 ohm for r2 but didn't use wander lead for r1 !

 

[telectrix]

test R! at each socket. from the readings you'll get an idea of how they are run. when you get to an open circuit, that's when to investigate. could even be something screwed on wall piercing the L. kitchen fitters are notorious for this.