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Peter Woodford

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AM I GOING MAD

Hi guys have been practising some testing today as have my assessment is in 2 weeks have carried out continuity testing on a ring and all readings seem fine, but when it comes to insulation resistance testing I must be doing something wrong am getting readings of o.oo megaohms on carrying out these tests at 250v and 500v please help.

many thanks
 
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Guest123

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  • #2
Hi Peter.

You can still have ins res faults, even with perfect continuity readings. When you say you have done continuity tests on the ring is that P-P, N-N and E-E?? also R1+R2 or R2??

Also your ins res readings, are they down between P-E, N-E or P-N or all 3??
 
peter readings like that would sugest there is a load plugged into the circ, also remove neutrals for said circ from cu to test to prevent faults on other circs showing on the one you are testing
 
P

Peter Woodford

  • Thread Starter Thread Starter
  • #4
Hi Peter.

You can still have ins res faults, even with perfect continuity readings. When you say you have done continuity tests on the ring is that P-P, N-N and E-E?? also R1+R2 or R2??

Also your ins res readings, are they down between P-E, N-E or P-N or all 3??
carried out P-P 0.29,N-N 0.29 and E-E 0.41 and R1 + R2 was 0.64 and all the reading seem to be down on inulation resistance

thanks
 
P

Peter Woodford

  • Thread Starter Thread Starter
  • #6
r1 & r2 should be about .17 have you done figure of 8 with your L & cpc

thinking about it i don't think i did cheers

what can i do about the ir results this seem to be on a number of circuit don't know if im doing it right
 
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G

Guest123

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  • #7
Hi.

Have you disconnected all electronic equipment before stsrting the test - neons in fused spurs, cooker switches, shower pullcords. Dimmer switches, light bulbs fluorescent fittings etc??
 
P

Peter Woodford

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  • #8
Hi.

Have you disconnected all electronic equipment before stsrting the test - neons in fused spurs, cooker switches, shower pullcords. Dimmer switches, light bulbs fluorescent fittings etc??
disconnected every thing as far as im aware

line to line
line to neutral
neutral to cpc
line to cpc

on a ring this is right isn't it
 
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S

Spudnik

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  • #9
Yes, except you dont do the line/line as this would create a flat reading as you are, in effect, shorting the test leads via the ring 'live' conductor.

You only do this on 3 phase.

Also, as above, remove each circuit in turn and carry out the tests.
 
P

Peter Woodford

  • Thread Starter Thread Starter
  • #10
If I still don't get the right readings for this were do I go from here
 
S

Spudnik

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  • #11
OK.

Lets start at the beginning...

As a starter..

Power up all the circuits.

Go round and switch on ALL the lights, then, go round again and make sure you switch them ALL off.

This way, you should be fairly sure there are no loads on the lighting (check loft for socket for booster and unplug.

Next is to go around and unplug everything, switch off spurs, cooker isolators etc.

Back to the CU. All fuses out or MCB's off, main switch off.

Next, set your tester on 250V (for now) and start with the red lead at the outgoing side of the fuse/mcb, and black on the neutral bar.

Test each circuit, leaving the probe on the neutral.

Once done, transfer to the CPC bar and repeat.

Finally, probes on neutral bar and cpc bar.

Now, if there are any circuits that are still showing flat, you need to establish what they do, disconnect them completely from the cu and test again.

If it is still showing flat, then you either still have something plugged in/switched on, or there is a damaged or trapped cable in the ciruit somewhere.


As a final point, if the CU incorporates RCD's then its unlikely you have a fault, as the RCD is not picking anything up. Not always the case tho.

Other than that, its down to a process of elimination to find the fault, and im afraid that all comes with experience!!

Just to make you feel better, im finishing some flats that were started by another sparks, and yesterday, carried out final testing, connected up CU, switched on one of the lighting circuits and 'BANG!'.

All finished and painted so i now have to start taking up chipboard flooring to trace the cables!

Wish me luck!
 
S

sivoodoo

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  • #12
How did the chipboard flooring go?, and good post bye the way.
 
K

kung

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  • #13
Try testing board as a whole and isolating circuits one by one you might even have a low energy light fitting in/garage-shed power with things plugged in etc.
 
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spark1

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  • #15
Jason if you carried out final testimg how did it go ! BANG! ?
 
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