continuity of ring circuit

[bigQ]

Hi,
I carried out a test on the downstairs ring.
R1 read as 0.58 ohms
Rn read as1.39 kilo ohms
R2 read as 1.19 ohms.

A socket test of L-N gave readings ranging between 0.11 ohms through to 0.45 ohms.
one socket gave a reading of 2.30 ohms.
I have checked it and there are no loose connections, and is wired correctly.
there are 2 cables feeding it.
when I tested the L-cpc, readings ranged from 0.33 ohms to1.18 ohms.
the pre mentioned socket read as 1.61 ohms.


I have a megger 1552 mft.
other tests on it give expected readings.
sometimes when I check something a second time straight away for peace of mind, I might get a slightly differant reading.
I have put a plug in socket tester on all of the sockets, and it indicates everything is ok, and when used, nothing trips.
is there some fault with the neutral?, or is my mft in need of a check.

and just another quick question, when I tested the external loop impedence, it tripped the main switch. Could this be because of the rcd's, or do I need to disconnect the bonding for the main water and gas first, would not disconnecting them cause the test to trip.
all other tests were fine. Rcd, ramp etc.

 

[Taylortwocities]

Hi,

R1 read as 0.58 ohms
Rn read as1.39 kilo ohms
R2 read as 1.19 ohms.

You need to sort out the rn issue. it should be about the same as r1.

when I tested the external loop impedence, it tripped the main switch. Could this be because of the rcd's, or do I need to disconnect the bonding for the main water and gas first, would not disconnecting them cause the test to trip.
all other tests were fine. Rcd, ramp etc.

Tripped the MAIN SWITCH? MAin switches do not trip, they are supposed to be just SWITCHES. Unless you are using an RCD as the incomer…..that is not recommended as it wrecks the concept of segregation of circuits.

 

[bigQ]

Hi, thanks for replying,
I'm aware the rn should be the same as r1, which is why I'm asking if anyone knows if its a fault in the circuit or not.

There is a separate main switch between the meter and cu. Is that what would be tripping the test?

 

[bigQ]

Hi, thanks for replying,
I'm aware the rn should be the same as r1, which is why I'm asking if anyone knows if its a fault in the circuit or not.

There is a separate main switch between the meter and cu. Is that what would be tripping the test?

 

[Taylortwocities]

Hi, thanks for replying,
I'm aware the rn should be the same as r1, which is why I'm asking if anyone knows if its a fault in the circuit or not.

There is a separate main switch between the meter and cu. Is that what would be tripping the test?

Its a fault in the circuit.
Continuity is the very first dead test before anything else. Fix the fault and carry on dead testing. Live testing comes MUCH LATER.

 

[bigQ]

I changed the cu, and did the tests in order. I just can't fathom this fault. Do you think it's a fault at a socket, or a fault hidden under the floor boards.
There is a old switched fuse in the ring, no idea what it was for, not used now.
The wiring is at least 30 yrs old,

 

[Gaz the Sparky]

I changed the cu, and did the tests in order. I just can't fathom this fault. Do you think it's a fault at a socket, or a fault hidden under the floor boards.
There is a old switched fuse in the ring, no idea what it was for, not used now.
The wiring is at least 30 yrs old,

Are you a qualified electrician ? This is simple stuff if you are there's a fault on the ring main somewhere you have to carry out simple fault finding to find it

If carrying out a earth fault loop test it will trip RCDs due to the test current hence why you have to test using a low no trip setting on the tester

If you have a RCD main switch protecting the whole board this doesn't comply as it doesn't give you segregation of circuits


G.T.S

 

[bigQ]

I have just passed all my courses, so yes to qualified.
in addition to that, think back to when you first started, did you know everything!
I know there's a fault, just wondering if anyone know's what it could be, save me loads of time searching for the fault.
that's all.

 

[Gaz the Sparky]

I have just passed all my courses, so yes to qualified.
in addition to that, think back to when you first started, did you know everything!
I know there's a fault, just wondering if anyone know's what it could be, save me loads of time searching for the fault.
that's all.

I rember when I first started it's actually not that long ago

Right you have a fault on the ring circuit if you have just recently qualified this should be fresh I'm your head.

Bearing in mind that you have continuity on r1 ,rn and r2 this confirms that the ring is indeed a ring if there was no continuity at all on any this confirms a phiscical brake in the cable.

Due to having continuity on r1,rn and r2 I would hazard a guess as a loose connection on the neutral connection and you have to take the socket fronts off and check the tightness of the connections. Due to a lose connection it's making continuity but is giving a high resistance joint.

It's just a matter of physically checking sockets to start off with check any that look dodgy or look like they have been removed recently. Any that are broken, covered in Water ect

You will probably find the neutrals pop out of the socket

 

[AndrewDavie]

What I'd do is disconnect at CU, connect L-N on one side.
On that side of the circuit, test Rn on each socket in order until the resistance jumps by an unexpected amount - that socket or the one previous will (probably) be the culprit.
Or at least that's another way of doing it without unscrewing and checking every socket.

 

[PrenticeBoyofDerry]

I changed the cu

Did you not carry out these tests prior to changing the CU?

and did the tests in order.

Well once you came to the Rn fault the testing should really then be stopped and remedial work done, as the rest of the tests are not much use until the Rn issue is resolved.

I just can't fathom this fault. Do you think it's a fault at a socket, or a fault hidden under the floor boards.

Could be a number of things, bad connection at joints I would look for first, doubt that a faulty socket would affect end to end readings!

 

[bigQ]

Thanks for the advice guys, will have another look at the connections.

 

[PrenticeBoyofDerry]

I assume you are testing T&E and have the correct legs of the circuit?

 

[RF Lighting]

and just another quick question, when I tested the external loop impedence, it tripped the main switch. Could this be because of the rcd's, or do I need to disconnect the bonding for the main water and gas first

You can not test for Ze with bonding connected.

FFS this is the most basic of basic stuff. It's the most important test on an installation, and you can't even get that right.

 

[flyingsparks]

May not be loose connection on the neutral but that it's pinched onto the insulation somewhere.