High EFLI

[bigtom]

Hello DIYnotters

I'm planning a career change into domestic electrics, and have bought a multi-tester so that I can practise onmy own house while training. I thought I should start with a safety check, so the first thing I did was to measyre EFLI using a socket, and i'm worred with the result. I don't know if the socket is on a ring main circuit, but I want to check that in daylight.

I followed the instructions to the letter, so checked first that earth of the socket supply is actually conencted to the main earth at the fuse box. The readings I got were between 2.5 and 2.85 ohms, but I was expecting no more than 1.5ohm.

Is this bad, and what do i do if it'is bad?

Hope someone can help.

 

[333rocky333]

was the lead plugged in a socket to test.
Check a few more sockets the others may give lower readings

 

[ColJack]

did you zero the leads?

do a Ze at the board and tell us what you get?
you also don't mention anything about the installation..
what earthing arrangement do you have?

 

[bigtom]

Hi thanks yes it was a kitchen socket. I've just looked in the fusebox and the kitchen seems to be on 3 direct cables. I tried all sockes on one cable and theyre all in that range i said before.

I'm goinf to measure other cables and see what they do.

Thanks.

 

[kai]

If the kitchen socket is off a single B16 breaker, the EFLI can be anything up to 3 ohms, so are you measuring off the fridge socket run from a B16 breaker perhaps? (My kitchen freezer circuit is off a single B16 breaker).

However the EFLI reading on my freezer circuit is 0.27ohms on a PME system.

 

[bigtom]

I've just been told in no uncertein terms to stop unplugging the fridg and everything so the other tests will have to wait til shes out.

 

[sparkyspike]

The reading you are getting is high for a ring final. As you are getting the same reading on the other sockets then it is probably a genuine ring (although it sounds like there is a spur wired into the breaker as well).

Do you know how to perform a loop test on the supply (Ze)? Also do you know how to do a continuity test on a dead ring circuit? You can add the Ze to the continuity result to calculate the Zs. If you don't want to test the live supply, then subtract the continuity reading from the Zs reading to get the expected Ze.

By doing this you will find whether the problem is from the supply or part of your installation. For example a TNS loop test normally comes out at something like 0.3 ohms. Anything over 0.8 ohms is too high. For B type breakers the maximum loop impedance is 46ohms divided by the rated current.

 

[bigtom]

Thanks kai the 2.85 was just a countertop socket not the fridge socket.

This socket is a double one and another double is on the same cable. Then there are 2 more double sockets on another cable and a single double on one cable. All 3 cables are in one MCB marked Wylex B32.

 

[bigtom]

Thanks sparkyspike I dont know yet how to do a continuity test but these sockets don't sem to be on a ring circuit cable.

How do I measure Ze? Can I do it without unplugging the fridg and losing my testacles?

 

[ColJack]

no..
you can't..

you take the cover off the CU, turn the big red switch off, pull the main earth out and do a loop test on the live side of the main switch and the earth..

not something recomended for someone who doesn't know what Ze is to start with..

 

[sparkyspike]

No, you have to turn the power off. It is a live test using probes and not recommended without some guidance. You can call your supplier for a reading if you like, or read up on Ze testing and working with live conductors before you attempt it. You also need to read up on supply types (TN, TT).

Also read up on testing ring continuity and circuit impedance.

 

[bigtom]

Thaks coljack I didn't know what Ze was, but am reading about it and I'm a fast learner.

 

[spark1]

Bigtom it looks to me you have a TNCS or TNS supply system with a Ze of maybe approx 0.16 ohms [ speculative statement]
I would say the two cables with two sockets on each are two ends of an original ring final circuit which somebody has split somewhere...the other cables with one socket on it is a spur direct from the mcb.
You will need to do a full continuity test on the ring circuit L-L. N-N. and CPC-CPC. and also eventually calculate R1+R2. With a bit of luck you will find part of the ring conductors still forming a loop. you will have to back off all the sockets to find this split and rectify it. If all the conductor loops are broken then you will have to remake the ring or derate the mcb to 16A or 20A.

 

[Spark123]

As others have said, do a Ze test and post the result.

 

[niceguy235]

I cannot actually believe what i am reading..

Are ANY of you qualified electricians??????

Not ONE of you has asked what type of earthing system he has.

And you are telling him to do a Ze and he hasnt even got a clue what that is.

May i suggest to the OP that he gets himself enrolled in a training centre and learns from the beginning properly rather than through a forum, before he kills himself or his family.

I despair.

Its no wonder this industry is in the **** state that it is.