Help with testing

[gaz2509]

hi all, just trying to get into some electrics, basics, been working as a free helper to get used to some for a friend of mine but im struggling to get my head around the R1+R2 TEST.

ok i have tested my own house

r1 = 0.63 so divide by 4 = 0.15
rn = 0.60 so divide by 4 = 0.15
r2 = 0.92 so divide by 4 - 0.23

therefore am i right in saying

R1+ R2 = 0.15 + 0.23 = 0.38?

however on the R1+rR2 test i actually get 0.49 at furthest socket on the circuit? so thats where im confused?

all help appreciated

 

[riveralt]

You need to explain how you are conducting the R1+R2 test - in detail?

Lets hope it is a dead test!!!

Which type of circuit you are testing - ring or radial?

Looks like its a ring....

Are you doing testing in the correct sequence.

What are you end to end results.

What is your actual R1+R2 result?

Should you really be testing if you don't understand what you are looking for?

 

[gaz2509]

yes testing im doing is dead testing.

it is a socket ring main 32amp mcb.
to test i.

place a temporary link between earth and live at c/u then test between live and earth at each point on the circuit, as to pg 79 of osg continuity test method 1...


end to end results are.what i listed above

end to end of live = 0.53
end to end of neutral = 0.58 (i believe 0.5 tolerance is allowed)
end to end of cpc = 0.89

 

[riveralt]

Try looking at page 80 of the red OSG paragraph 10.3.2. that actually discusses how to conduct continuity tests on ring circuits, rather than the radial circuits you appear to be referring to.

 

[gaz2509]

yes and that is exactly how my testing has been done, upto step 1, then ive done step 2 and also step 3.

 

[gaz2509]

sorry yes this is how my testing is done for a ring circuit.

i seperate the ring at c/u and test l to l

n to n

e to e

 

[riveralt]

Have a look at this video.

It is conducted on a three phase board but the guy is actually testing a ring circuit.

Couple of issues - he makes a bit of a mess on the safe isolation procedure in so much that he doesn't check the tester before starting -

The line neutral and cpc are all the same size unlike most domestic situations.

http://www.electriciansblog.co.uk/2010/02/ring-main-testing-video/

 

[riveralt]

sorry yes this is how my testing is done for a ring circuit.

i seperate the ring at c/u and test l to l

n to n

e to e

Once you have seen the video it might become a bit clearer.

I take it you understand why you are doing these tests and their relationship to the other tests - like the earth loop impedance Zs, the external earth loop impedance Ze, the Prospective earth fault current and the prospective short circuit current. Not forgetting Insulation resistance.

The purpose of testing is not only to make sure the characteristics of the circuit are within the guidelines and will safely automatically disconnect the supply in the case of a fault - it also there to help diagnose faults.

If you are leaping into testing without understanding the basics of how electrical installations work then I would respectively suggest you stop and enrol at a local college so that you can fully understand what and why we do test.

 

[gaz2509]

HI HAVE LOOKED AT VIDEO, AND THIS IS HOW IM DOING MY TESTING.

i have supplied my end to end results on my first post and also the R1 +R2 result i got at the furthest soclet on the circuit. but im wondering how to check its correct as if i do the equation i stated in first post it doesnt give me the R1~+R2 value i got at last socket

 

[gaz2509]

sorry yes this is how my testing is done for a ring circuit.

i seperate the ring at c/u and test l to l

n to n

e to e

Once you have seen the video it might become a bit clearer.

I take it you understand why you are doing these tests and their relationship to the other tests - like the earth loop impedance Zs, the external earth loop impedance Ze, the Prospective earth fault current and the prospective short circuit current. Not forgetting Insulation resistance.

The purpose of testing is not only to make sure the characteristics of the circuit are within the guidelines and will safely automatically disconnect the supply in the case of a fault - it also there to help diagnose faults.

If you are leaping into testing without understanding the basics of how electrical installations work then I would respectively suggest you stop and enrol at a local college so that you can fully understand what and why we do test.

yes i understand the other tests, it is just this one i cant seem to get to grips with, like i said im helping a friend for free aswell as attending c&g courses and was just after some extra advice

 

[riveralt]

The could be several reasons why your ( R1+R2) does equate to the (r1 + r2)/4 reading you got at the end of the circuit - and this is my point about understanding the basics.

Did you check the readings for R1+RN at each point on the circuit what was the result there?


You could be taking a reading from a spur.
Your may have a loose connection at the terminal.
Is this the only socket where the problem exists - split the circuit and try to determine which side of the circuit the problem originates.
Do the reading rise as you test the sockets away from the CU up to this socket and tail off again as you move back to the CU?

The bottom line is that the reading should generally be the same all the way around the final ring main if not then you need to investigate.

 

[riveralt]

The figures you have given for end to end and those you have spoken about in your first post are different, why?

The end to end line is r1
The end to end neutral is rn
The end to end cpc is r2.

The ratio of cpc to line is spot on - so what are the r1 etc figures in the opening post?

 

[ban-all-sheds]

r1 = 0.63
rn = 0.60
r2 = 0.92

end to end results are.what i listed above

end to end of live = 0.53
end to end of neutral = 0.58 (i believe 0.5 tolerance is allowed)
end to end of cpc = 0.89

 

[riveralt]

r1 = 0.63
rn = 0.60
r2 = 0.92

end to end results are.what i listed above

end to end of live = 0.53
end to end of neutral = 0.58 (i believe 0.5 tolerance is allowed)
end to end of cpc = 0.89

That's what I pointed out to him BAS, wondering why he hasn't replied.

 

[holmslaw]

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