ELECSA Certification Scheme Ring final continuity readings and Elecsa assessment looming...

[mpoy222]

Hi
I have my Elecsa assessment in under two weeks and ive never felt so stressed in my life! I've changed my C.U. to use as my job as i thought it would be easier but im really struggling with the testing especially on the downstairs ring final sockets. Ive done end to ends and got Line 0.61ohms Neutral 0.60ohms cpc 0.40ohms. I done crossover test on L-N and got fairly consistent readings of between 0.30 and 0.35ohms. Then i done the line-cpc crossover and at the C.U. got 0.28ohms then the first few sockets (in the kitchen) where around 0.35ohms then the next few jumped to around 0.43ohms (not even spurs). Im certain i have the opposite legs connected in the C.U. and ive checked almost every connection i can especially where there is a sudden rise. Main earth and bonding was disconnected to stop parallel paths. The house is only 7 years old so 'shouldn't' have any nasty wiring surprises. Any ideas??? Anything im missing or should try? If i cant find any faults will i just put it on the EIC. Panic is setting in and i feel very stupid. Any help would be greatly appreciated.
Michael

 

[Sharpend]

Was there any alterations to the electrics when kitchen was done?

sorry now read rest of post,
Is it the original Kitchen?
have you worked the split ring method?

 

[mpoy222]

No its the original kitchen from when the house was built.

 

[Sharpend]

Have you got GN3 inspecting and testing?
what other tests have you carried out on circuit?

 

[markc123]

Are the sockets wired in 2.5/1.5 ?

If so, the cpc value (you have 0.40ohms) should be 1.67 x greater than the 0.60value you've got for the line.

This would tie in with your other readings that are funny - line to cpc crossover.

You checked for parallel paths?

 

[Richard Burns]

Your end to end resistance for the cpc is very low it should be about 1 - 1.2 ohm (from the L and N readings), so there may be an interconnection on the cpc, possibly via supplementary bonding somewhere into a socket.

However based on your readings taken then you should be getting about 0.25 ohms for L-E ring test.

It is possible that you are just getting contact resistance at the plugs and if you push the tester in and out of the socket a few times, or switch the switch back and forth it may reduce the reading.
Alternatively try testing at the back of the sockets.

 

[mpoy222]

There are a lot of FCU's in kitchen feeding everything from washing machine to under cupboard lights, fan, hob, cooker hood etc. No i dont have GN3 i thought i had spent enough on books and couldnt justify another £26 lol I havent carried out any other tests on the circuit as i run out of time. I havent tried the split ring method do you mean break the circuit down and test between sockets?

 

[Octopus]

There are a lot of FCU's in kitchen feeding everything from washing machine to under cupboard lights, fan, hob, cooker hood etc. No i dont have GN3 i thought i had spent enough on books and couldnt justify another £26 lol I havent carried out any other tests on the circuit as i run out of time. I havent tried the split ring method do you mean break the circuit down and test between sockets?

£26.00 that would be well worth spending IMHO.

 

[SirKit Breaker]

r1 = 0.60 and rn = 0.61, i would expect r2 if it is 2.5/1.5 to be about 1 ohm off the top of my head. If this is so, then R1 +R2 should be about 0.4 if the "ring" is a ring. The readings will jump about, due to poor leads, shaky fingers and a whole host of other reasons, dead testing is not an exact science. What is the EFLI like at each outlet, this may be a better indication of any faults present.

Cheers............Howard

 

[markc123]

They rob us all mate, you're not the only one - every ammendment is roughly £150 down the pan. GN3 would be advisable.

 

[SirKit Breaker]

£26.00 that would be well worth spending IMHO.

A lot cheaper than chucking the £500 plus quid that Elecsa will charge for a revisit down the bog, if he cant explain any given test procedure with some confidence!

 

[mpoy222]

Are the sockets wired in 2.5/1.5 ?

Yeah standard 2.5/1.5

Your end to end resistance for the cpc is very low it should be about 1 - 1.2 ohm (from the L and N readings), so there may be an interconnection on the cpc, possibly via supplementary bonding somewhere into a socket.

However based on your readings taken then you should be getting about 0.25 ohms for L-E ring test.

Yeah i thought thats what i would get from calcs and thought i was on track with the 0.28 reading at the board. Why would there be supplementary bonding into a socket?

It is possible that you are just getting contact resistance at the plugs and if you push the tester in and out of the socket a few times, or switch the switch back and forth it may reduce the reading.
Alternatively try testing at the back of the sockets.

​

Tested at back of sockets too and got the same.

 

[Richard Burns]

You need to find out what has happened with the cpc, if you have checked the sockets then you would have noticed extra cables so a bit lost without seeing the site.

Try and cpc end to end at a socket and see if you get different values from the CU. Might help narrow down the problem.

 

[mpoy222]

A lot cheaper than chucking the £500 plus quid that Elecsa will charge for a revisit down the bog, if he cant explain any given test procedure with some confidence!

To be honest i am lacking confidence in testing hence why im asking for help. Its been a while since i done any and its easy when you get the results your expecting but my lack of experience shows through when things aren't how they should be. I have numerous testing books as well as the necessary regs books etc including an NICEIC testing book i was given when i done my C&G 2392 (also have 17th and C&G2330 L3 etc) , this is pretty thorough and i think covered everything the GN3 book had so i didnt want to buy it just because people were saying its another book i should have. The money i have spent is not worth thinking about just be able to offer to work!

 

[mpoy222]

You need to find out what has happened with the cpc, if you have checked the sockets then you would have noticed extra cables so a bit lost without seeing the site.

Try and cpc end to end at a socket and see if you get different values from the CU. Might help narrow down the problem.

Yeah i didnt think of trying that it does look like theres a parallel path then if the readings low then? Some of the FCUs are to integrated appliances so I cant get to the actual socket or connection for them. I dont know where or why there would be supplementary bonding going to any of the sockets though. I'll get to the bottom of it though so cheers for your help.
​

 

[markc123]

You got a heater in the bathroom thats bonded on a FCU, anything like that?

It's difficult when we're not on the job with you to say for certain over the web.

 

[mpoy222]

You got a heater in the bathroom thats bonded on a FCU, anything like that?

It's difficult when we're not on the job with you to say for certain over the web.

No nothing like that, I've disconnected main and sup bonding in C.U. too. I cant think of what else would be bonded to a socket and if ive disconnected bonding in C.U. would it still have a parallel path? I know what you mean though i bet if one of you guys was here you would be able to sort it in 5 minutes lol Its just frustrating i cant find the fault quicker.
​

 

[markc123]

You're just going to have to energise again, and switch off the ring-main (the one in question if you have several) and go around with a plug in tester (or a kettle if you don't have one lol) around absolutley every socket thats on the circuit and jot them down...then switch off and go around each one checking for connections to earth.

One of the things you need to understand is that a Parallel earth path will bring the cpc reading (R2) down towards 0. Your cpc value is at 0.40 compared to 0.60 and 0.61 with line and neutral. This is why im leaning towards a parallel earth somewhere.

You got SWA on the ring at all anywhere?

 

[onions1066]

Stand back and take a few mins, strip it down, can you actually see you have the right earths? Is the heating system on the ring? If it is that is prime for bringing your reading down reading through all the pipe work connected to the boiler .

 

[markc123]

It's late, and i'm not quite sure why i've just told you to energise the circuit. Have you had the power back on at all on the circuit since you've done the CU change...? If you have then crack on and do it again so you know whats what.