Final Ring Testing

[AdamGT3]

These are the results for the test on our main ground floor ring, the phase/cpc resitance test seems a bit odd what may be going on?

Continuity Phase/Neutral 1.99 ohms
Continuity Phase/cpc 2.98 ohms
Continuity Phase/Neutral at each socket .46ohms all within .05 other than spurs at .59
Continuity Phase.cpc each socket .62 ohms all withing .05 except spurs at .81
Resistance Phase/Neutral >500mohms
Resistance Phase/cpc 55mohms
Resitance Neutral/cpc >500mohms
Resistance Phase+Neutral Connected/cpc 16mohms

Thaks guys

 

[Lectrician]

Seems OK - The Phase and Neutral will most likely be 2.5mm/sq and the CPC will be 1.5mm/sq.

Assuming a standard ring with 2.5/1.5 T+E.

 

[JohnD]

But:

Resistance Phase/Neutral >500mohms
Resistance Phase/cpc 55mohms
Resitance Neutral/cpc >500mohms

Is there a washing machine or water heater or oven plugged in?

Or anything where the Earth and Neutral might have been wired to the wrong terminals?

 

[AdamGT3]

No nothing.

Tested prior to plastering to make sure everything OK, all connections made with connector blocks to complete the ring.

 

[JohnD]

Try halving the ring and retesting to find where it's coming from.

 

[AdamGT3]

How do you half the ring?

 

[JohnD]

OK. I mean, disconnect the block or socket at the midpoint, so it turns into two equal radials instead of a ring. Disconnect at the CU as well. Test each "half" and see if it has that strangely low resistance CPC/Phase. Hopefully it will be on one half and not the other. So you know the wiring on the other is OK.

Then spilt the half with the fault on it, and test again.

Keep halving the part with the fault on it until there is only one segment of cable left. That must be where the fault is. If you can't see it to correct it, pull out the faulty bit and put in a new length.

(Halving also works if you have a faulty outlet or connection, it helps you find it)

 

[Lectrician]

55M is still way above the limit where you should be concerned.

Agree, I would usually want to take a squiz.....but the results are fine.

 

[AdamGT3]

Thanks Guys

John, have done as you said and located the prblem in minutes, builder has nicked one of the cables clean through the sheath and nicked the phase.

Glad to have found it before it was plastered in.

 

[securespark]

Agree, I would usually want to take a squiz......

Well, you know where the loo is....

 

[JohnD]

Agree, I would usually want to take a squiz......

...onto the cable, and detect any exposed conductors that way