Testing and Inspecting

[Sparky Ninja]

now haveing done the continuity of protective conductors and CPS ( i dont mean to sound stupid but I would take the R1+R2 reading for all the circuits on the board at the same time wouldnt I)


I will need to move on to continuity of ring final circuits I will need to test end to end on the following r1-r1, r2-r2 and rn-rn

to do this I use the low resitance ohm meter setting again and apply one crocidle clipped lead to the line going out to the ring and the other crocidile clipped lead to the line comeing back in (thats r1-r1)

I do the same again but this time on the neautral (rn-rn) and then finaly the cpc (r2-r2)

this will tell me if I have continuity on each conductor in the ring circuit

all values should be within 0.05 ohms of each other if the conductors are the smae size

next I have to connect the line and neautral conductors together so that the outgoing line in connected to the returning neautral and vice versa. I then take a socket adaptor and take reading between the line and neautral at each socket by putting the test probes into the holes on the socket adaptor. If i get a higher reading from one of these sockets it is going to be the spur.

I can then do the same again useign the earth (r2) instead of the rn

this test should also enable me to confirm polarity on the ring

Remember also to carry out FUNCTIONAL CHECKS when doing R1&R2 tests. A good habbit to have is to switch every socket and switch off when you initially approach the rig, so you can be reminded to carry out a functional by default when you are forced to operate the switching to obtain a value.

 

[Sparky Ninja]

right next up then will be the insulation resistance test.

haveing made sure any sensitive equiptment is dissconected I would select the 500 V dc option (do I remove the main earthing terminal as to get rid of any paralell paths ?)

I will need to attach one crocidile clipped lead to the line conductor and the other to neautral conductor and press test on the megger I should expect a reading of >299 M ohms on the tester I will be useing

next I test between the line conductor and the main ear bar in the consumer unit again expecting a reading of >299 M ohms and then finally between the neautral and main earth bar in the consumer unit again looking for a >299 M ohm reading.

if the reading is less then 2 M ohms i will need to investigate as to why this is although the regs state that the minimum allowable reading for insulation resistance is 1 M ohm

Remember to put all switches in the closed position (on) and if there are any two way switching then the tests to line will need to be done twice, with the operation of a switch in-between to include BOTH of the strappers under the test.

 

[lofty84]

ok next I think is checking that the polarity of circuits is correct which i think I would have done useing method 1 when checking the contiunity of protective conductors and continuity of ring final circuits

I will still need to confirm that the breaker and switch are on the line conductor, how do I do this

is it

to test the polarit of the supply

for this I will want to test between the distributors incomeing line and neautral conductors looking for a 230V reading

and then between the Line and Earth looking again for 230v

finally the Neautral and earth but this time I should get a reading of 0 volts if the poalrity of the supply is correct

 

[lofty84]

again well spotted mate a very good point which im hopeing to remember ...

 

[lofty84]

i dont know how many tests in I am at this point but next I think is the external earth fault loop impedane test Ze

for this I deffo need to disconect the main earthing conductor as we dont want any paralel paths. I take my megger and select the external earth fault loop impedance setting and attach one crocidille clipped lead to the main earthing condutor that I removed from the main earth bar in the consumer unit and then with the other lead put the probe on the incomeing line conductor.

depending on the earthing system I have i should expect reading that are lower then the following for each earthign sytem

tncs <0.35 ohms tns ,o.80 ohms tt < 200 ohms

fingers crossed thats right

 

[Sparky Ninja]

ok next I think is checking that the polarity of circuits is correct which i think I would have done useing method 1 when checking the contiunity of protective conductors and continuity of ring final circuits

I will still need to confirm that the breaker and switch are on the line conductor, how do I do this

is it

to test the polarit of the supply

for this I will want to test between the distributors incomeing line and neautral conductors looking for a 230V reading

and then between the Line and Earth looking again for 230v

finally the Neautral and earth but this time I should get a reading of 0 volts if the poalrity of the supply is correct

Dead Polarity -

Verified by method 1 excluding socket outlets, however R1&RN will confirm polarity. So R1&RN will be a MUST for rings & radials.
Confirm switching in the Line conductor only can be partially verified by method 1, but in the case of double pole isolators and motors, functional checks will also contribute.
Also consider the switching of multi pole devices, shower fan isolators etc.
Plus the centre contact of an ES lampholder must be connected to the Line conductor.

Live Polarity -

Is as you've described, but be sure to apply the indicator to the Line last, and remove it from the Line first. - 'Line on last, Line off first' - Try to remind yourself of that.
If you carry out test between the Earth and Neutral last, then recheck the detector by re-applying it to Line to verify it' working (proving on a known live supply).

 

[Sparky Ninja]

i dont know how many tests in I am at this point but next I think is the external earth fault loop impedane test Ze

for this I deffo need to disconect the main earthing conductor as we dont want any paralel paths. I take my megger and select the external earth fault loop impedance setting and attach one crocidille clipped lead to the main earthing condutor that I removed from the main earth bar in the consumer unit and then with the other lead put the probe on the incomeing line conductor.

depending on the earthing system I have i should expect reading that are lower then the following for each earthign sytem

tncs <0.35 ohms tns ,o.80 ohms tt < 200 ohms

fingers crossed thats right

That's fairly spot on. Nice to hear someone using two lead meggers in training now.

If you had to remove the lock off to remove the cover, be sure to replace it before removing the Earthing conductor.
You may measure a higher value than anticipated, this would depend on weather the test rig is close to the origin or downstream plugged into a final circuit of some kind. If the latter is the case then be aware that it's not the true Ze you are measuring.
The college may provide you with a more accurate Ze value if this is the case.

 

[lofty84]

is anyone able to tell me how to do the PEFC test please

 

[i=p/u]

just flick the switch on your megger after your performing Ze test but have bonding conductor connected for this....

 

[lofty84]

after the pefc test it time to move on to the live tests which are the earth fault loop impedance test which is simply a case of selecting the no trip setting and plugging the tester into all sockets takeing the highest reading i think ???


finaly its the rcd tests where i need to test 1/2 1 and 5 x I delta n at both o and 180 degrees.


i hope i can remeber all this as all ive got left is these two practicals

 

[lofty84]

just flick the switch on your megger after your performing Ze test but have bonding conductor connected for this....

so basically after dong the ZE test reconnect the main earthing condutor and select the pefc setting on the megger hit test and it will tell me the result ..

 

[Des 56]

Remember
Prospective fault current is the highest value of the results of
Prospective short circuit current and
Prospective earth fault current
and that value should be recorded on the test results

 

[telectrix]

after the pefc test it time to move on to the live tests which are the earth fault loop impedance test which is simply a case of selecting the no trip setting and plugging the tester into all sockets takeing the highest reading i think ???


finaly its the rcd tests where i need to test 1/2 1 and 5 x I delta n at both o and 180 degrees.


i hope i can remeber all this as all ive got left is these two practicals

don't forget to test with test button as well