no resistance end to end on L & N

[Ross1]

Hi, Im doing a end to end continuity on the house ring but am getting 0.00ohms on L -L & N -N but getting 0,42 ohms on E - E.

Ive done a point to point check right around the ring, all seems good but when I tested again I`m getting same results.

thanks

 

[malcolmsanford]

Is there 2 RFC and have you got the right ends ?

 

[Marvo]

Try using an analogue tester instead of a digital one, it will be less sensitive to induced surface voltages etc..

 

[robd]

split the ring in half and test continuity from the board to the point where you've split in half, if you've got continuity on one end but not the other work your way back round until you find the break in the circuit. What I mean by this is take a socket off the wall at a point you think is halfway, don't screw anything back on the wall until you've sussed it or else you'll spend your time doing the okey cokey with them. Think about it logically and all will become clear If for example someone's screwed through a cable it's unlikely they would've gone through the live and neutral conductor without hitting the earth, assuming it's wired in twin and earth

 

[robd]

and make sure you aren't using the wrong cable to try and get a reading off, have a good root round in the consumer unit and check you're not testing an end of the ring with another circuit

 

[gnselectricals]

Have you nulled your leads properly as you would usually see +2000 ohms not 0.00 if open circuit
Regards gram


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[telectrix]

i would say that the 0.42 is sensible. it's the 0.00 that you should be concerned about.

 

[robd]

sorry mis-read, 0.0 obv not open circuit so ignore me teach me to try and get technical on a Sunday! 0.0 might be right if you've got a rfc covering a very small area, failing that check your leads!

 

[Marvo]

i would say that the 0.42 is sensible. it's the 0.00 that you should be concerned about.

Yep, it was the 0.00 I was worried about, might be the high input resistance of a digital tester picking up RF or induced voltages.

 

[telectrix]

could try measuring with board isolated so all other circuits can't affect the reading with induced volts etc.

 

[Harry Worth]

Is it a Doll's house?
Or - On a ring final. 2.5mm2 Neutral and Live. 1.5mm2 on the CPC. The resistance of CPC end to end should be 1.67x higher than N & L end to end readings. In your case with .42 Ohms then the end to end readings should be circa .25 ±0.05 Ohms. Readings should be within 0.05 Ohm so 0.2 - 0.3 Ohm. (Still learning so please kick me where appropriate)

 

[Richard Burns]

I have a circuit in my house where the "ring" goes out to the shed but it is joined together in a connector block before it leaves the house, I have not tested it but this may well give similar results to the OP. e.g. has someone crossed the ring or joined it at the first socket out.

 

[telectrix]

I have a circuit in my house where the "ring" goes out to the shed but it is joined together in a connector block before it leaves the house, I have not tested it but this may well give similar results to the OP. e.g. has someone crossed the ring or joined it at the first socket out.

so why ain't you fixed it then. ???

 

[Richard Burns]

It is still cables in parallel CC is OK and in the words of so many customers it works! (sorry!)
Effectively unless there is a problem in the floor above the CU the connection into the CB is just a bit far away and one could consider it as a piece of 5mm going to start a ring 3m away and I am too lazy to take the floorboards up.

 

[telectrix]

fair enough. i have inherited a couple of unfused spurs on the rfc with 3 or 4 outlets on each. rather than spend hard earned on fitting FCUs, i've downrated the MCBs to 16A

 

[vernam616]

Split ring from a MR DIYER attempting some home electrics, thats what my cash is on

 

[telectrix]

nope. he's getting 0.00 ohms. could be his meter resolution is pants below , say 0.4ohms.

 

[vernam616]

The Megger multifunction tester i use does this sometimes, turned out the batterys were low in the kit, would just display "0.00ohms" when attempting continuity

 

[telectrix]

and don't the meggers just eat batteries. i'm sure megger hold shares in duracell.

 

[vernam616]

Correct !, 8 AA buggers too

Luckily the wholesalers always seem to have a offer on batterys, 8 duracell AA's for £2
I dont know why im complaining because i dont pay for them, the company does

 

[Ross1]

Well what a day guys, the job in question is my 1st NIC assessment job in the morning, I took the rfc apart, one leg in MCB tested point to point, powering on and off testing every end each time being very thourgh, and followed it around the house and came back to the disconnected end at the cu. retested and again 0.00 ohms on live and nuetral. tester just been calibrated, zeroed leads, all other circuits turned off. in the end I had to leave it otherwise I would not have finished in time for morning assessment. i took out the 32A MCB and replaced it with a 20A just incase. dont know how its going to affect my assessment in the morning which is a cu change by the way............what you think guys?

 

[Ross1]

still got all the paper work to do now aswell..........gonna be a long night, why do I leave things to the last minute.....Grrhhh

 

[Richard Burns]

Unfortunately if you do not have a compliant system it is difficult to complete the paperwork, however one could say that the CU replacement was successful but the circuit in question is faulty and has been disconnected. (pending further investigation!)
With a resistance of a 2.5mm cable being 0.008ohm/m you must have a link fault within 0.5m of the CU as anything above that would likely show as 0.01ohm and not as zero on the meter (depending on the meter resolution). Assuming your batteries are up to spec. in the meter.
Best way to test I would say is to disconnect all the RFC wiring from the CU keep all the ends separate join your meter with a long lead to one of the, say neutral, cables and go round each socket with the meter and test the resistance of that one wire (using a socket adapter); if the resistance is zero all the way round, then there is a problem with your meter, if the resistance increases up to the middle and then decreases as you reach the other end of the ring then the ring is linked close to the meter, if the resistance increases each time you move further away then try starting at the other end of the (in this case neutral) cable if again the resistance increases steadily... Ah bit stuck but you could use the largest value as close to n-n reading (no do not do that, that is wrong) but ring should be OK. Similarly with the line conductor.

Good luck with the assessment, do talk to the assessor and they should be understanding, they normally do want you to pass even if only to get your money!

 

[SPARTYKUS]

All been said already but put money on a JB close to CU with the join in!

 

[Ross1]

All been said already but put money on a JB close to CU with the join in!

me 2 mate, cheers

 

[Octopus]

Could you not say to the assessor that the job is WIP, outline the "issues" and steps, taken so far, to find the fault(s) and the "solutions" that you are considering??

 

[Des 56]

The test for ring continuity is a 3 step test, not just end to end
You have only identified a closed ring but not a satisfactory ring circuit

Your best bet would be to explain to the assessor that you have carried out the cross connecting ,but the results were as you have described
You have decided to treat the circuit as a radial,the zs maximum is the result you are then interested with

Because you have not tested for ring continuity with the 3 step test,if you tell him that you have carried out only end to end testing, he may be less understanding of you

 

[3wayselectrical]

Could be a fault on the meter, try measuring with another meter. I've had this with my Fluke 1650, I checked it against another multi meter and got a reasonable reading.

 

[BlueToBits]

Could be a fault on the meter, try measuring with another meter. I've had this with my Fluke 1650, I checked it against another multi meter and got a reasonable reading.

I apologise if I teaching my mother to suck eggs, but try checking the crock clips. On all the ones I've seen, only one side of the jaw (the fixed side) is connected to the cable, the other jaw (moving side) relies on the connection through the spring. You may have nulled out the leads on one or both of the moving jaws rather than the two fixed jaws together.

 

[Goody]

It's likely as BlueToBits said, you may have nulled out the leads on one or both of the moving jaws (hinged jaws) rather than the two fixed jaws together. If leads aren't nulled properly you will get all sorts of confusing readings.

Also replace the batterries.

Best of luck with your assessment!

 

[Knobhead]

This may come as a silly question but you did IR test the circuit first before any CR tests?

 

[Deleted member 38070]

i had this with my fluke 1651 i kept getting 0.00 ohms on my end to end test, i was in the middle of my NICEIC visit, the inspector told me to take the batterys out of the meter and wait for 10 seconds then pop them back in.... you wouldn't believe it until you saw it... nulled my leads then did the measurement again and it was 0.31... has happened sinse on a 1653 and the trick worked.... (sounds like BS but true)

 

[Marvo]

Easy as that....Glad it all worked out.