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Discuss No R1 on ring main? in the Periodic Inspection Reporting & Certification area at ElectriciansForums.net

C

Cirrus

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Wired a kitchen this week and the earthing system is TT with a 30mA RCD up front. Got round to testing and everything was going fine until I tried to test for R1. The reading I got was >2000 so basically showing open circuit. I have continuity and Zs but cannot seem to get my R1 +R2. I had this last week on a TT system and I know it can be calculated but can't work out why the Fluke MFT won't give me a reading when I don't get probs on any other earthing system such as TNCS / TNS. Is it just a fact that this happens with TT systems?
 
U

Unregistered

  • Thread Starter Thread Starter
  • #2
sorry to pick faults but if its showing open circuit on R1 how have you got continiuty?
 
G

Grae79

  • Thread Starter Thread Starter
  • #3
Or Zs?
 
T

TonyM58

  • Thread Starter Thread Starter
  • #4
Cirrus,

ok my head is fried now

R1?

how do you measure R1? or why?:rolleyes:

R2 yes, R1+R2 yes, but R1????

like to help fella, but i think you would need to explain this test to me:)

the type of earthing system will only affect your Ze,Zs, PFC's and possibly your RCD times.

and a 30mA up front? oh dear, may as well throw the regs away:eek:
 
C

Cirrus

  • Thread Starter Thread Starter
  • #5
Sorry, was typing this on the way out so think I have screwed up what I was trying to explain. Will have a look at the test sheet and come back to you. As for 30mA up front - it is an existing crabtree starbreaker board. I have just added a new ring and cooker circuit.
 
T

TonyM58

  • Thread Starter Thread Starter
  • #6
when you say 'up front', is the RCd being used as the main isolator in the CU?

be interesting to know about the R1 thingy.......:rolleyes:
 
C

Cirrus

  • Thread Starter Thread Starter
  • #7
yes, the rcd is also the main switch. Board is probs about 20 years old but am now confusing myself and think that it is a 100mA rcd
 
T

TonyM58

  • Thread Starter Thread Starter
  • #8
if its the main switch then it should be a 100mA S-Type
 

ian.settle1

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Mentor
Arms
Cirrus,

ok my head is fried now

R1?

how do you measure R1? or why?:rolleyes:

R2 yes, R1+R2 yes, but R1????

like to help fella, but i think you would need to explain this test to me:)

the type of earthing system will only affect your Ze,Zs, PFC's and possibly your RCD times.

and a 30mA up front? oh dear, may as well throw the regs away:eek:
Tony

If it's a ring circuit then he has got to measure r1, r2 & rn for ring continuity.

Maybe he is getting mixed up with upper and lower case letters.
 
T

TonyM58

  • Thread Starter Thread Starter
  • #10
could well be Ian,

of course if its r1 and its open circuit, then this would epxlain why hes still getting Zs (although at an untrue value)

just shows that the three stage ring test works!

regards

Tony
 
C

Cirrus

  • Thread Starter Thread Starter
  • #11
Ok, sorted. I was using a plug top with a link between live and Earth and the link had come out. Now, what worries me is the boards. They are old crabtree boards. The main earth is 6mm and the boards have a 80Amp 30mA RCD up front. I know it is ideal to renew the board but the council won't pay unless it is Cat 1 and essential. Surely this isn't 'essential' as it just means that when the RCD trips, every circuit is affected.
Thoughts gents.......
 

ian.settle1

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Mentor
Arms
Ok, sorted. I was using a plug top with a link between live and Earth and the link had come out. Now, what worries me is the boards. They are old crabtree boards. The main earth is 6mm and the boards have a 80Amp 30mA RCD up front. I know it is ideal to renew the board but the council won't pay unless it is Cat 1 and essential. Surely this isn't 'essential' as it just means that when the RCD trips, every circuit is affected.
Thoughts gents.......
And the council LABC are supposed to certify work is ok under Part P when notified..:rolleyes::rolleyes::rolleyes:

What a bloody good laugh sounds like do as I say but not as I do...:rolleyes::rolleyes::rolleyes:
 
T

TonyM58

  • Thread Starter Thread Starter
  • #13
Ok, sorted. I was using a plug top with a link between live and Earth and the link had come out. Now, what worries me is the boards. They are old crabtree boards. The main earth is 6mm and the boards have a 80Amp 30mA RCD up front. I know it is ideal to renew the board but the council won't pay unless it is Cat 1 and essential. Surely this isn't 'essential' as it just means that when the RCD trips, every circuit is affected.
Thoughts gents.......

Ok,

glad you got your readings sorted

bottom line is that this breaks a number of regs (16th edition). It depends if the council 'defines' what Cat I is. When an old dear falls down the stairs due loss of lights due to a spurious trip on an unrelated circuit, they may take notice, particularly if sued.......
 
C

Cirrus

  • Thread Starter Thread Starter
  • #14
I know Tony - so what do the regs state?
 
T

TonyM58

  • Thread Starter Thread Starter
  • #15
Ok, sorted. I was using a plug top with a link between live and Earth and the link had come out. Now, what worries me is the boards. They are old crabtree boards. The main earth is 6mm and the boards have a 80Amp 30mA RCD up front. I know it is ideal to renew the board but the council won't pay unless it is Cat 1 and essential. Surely this isn't 'essential' as it just means that when the RCD trips, every circuit is affected.
Thoughts gents.......
well it breaks a number of regs (16th edition) and is a safety matter if an old dear falls down the stairs due to loss of lights after a spurious fault on an unrelated circuit trips the RCD
 
C

Cirrus

  • Thread Starter Thread Starter
  • #16
I understand the H&S aspect but am not sure exaclt what regs it contravenes:eek:
 
T

TonyM58

  • Thread Starter Thread Starter
  • #17
Cirrus

i can quote the regs to you tomorrow when i got the book in front of me

main one is seperation of circuits, then theres the requirement for an RCD used as amain isolator to minimum 100mA S type

If, for example, you had smokes installed you can also be contravening seperate BS regs

get back to you tommorrow
 
M

Mutts

  • Thread Starter Thread Starter
  • #18
Hey cirrus

sorry to get involved this late but i have only just started to use this forum, Anyway heres my understanding of what going on.

r1 = the end to end reading on the phase conductor on the ring
r2 = the end to end reading on the on the cpc (earth) conductor on the ring
rn = the end to end reading on the nuetral conductor on the ring

these readings should be taken at the consumer unit using a low ohms continuity tester.

so if you are not getting an end to end reading on the phase conductor you are not getting an r1 reading. which would suggest that somewhere on the ring circuit the phase coductors have seperated. (eg fallen out of the back of a socket outlet or been damaged in some way) ive also had cases where the grubb screw on the socket outlet has been screwed against the insulation and is not making contact with the copper conductor inside so look carefully. if your really unlucky the problem could be in a junction box somewhere.

The reason why you are still getting a zs reading is because the ring circuit is fed from both "legs" of the ring

hopefully you'll find it but if you don't you need to seperate the ring main and create 2 x 16 amp radial circuits.

As for the RCD protection on a TT system. You need to have a 100ma RCD time delay mainswitch But you need to make sure you also have 30ma RCD protection on the usaul circuits ie Socket outlets, showers etc. Are there RCBO's available for the consumer unit you are dealing with?

Its always worth doing all your essentail tests before working on existing circuits as well as after at least you know what your up against from the beginnig

Good luck dude.........Mutts
 
S

Shakey

  • Thread Starter Thread Starter
  • #19
Hey cirrus

sorry to get involved this late but i have only just started to use this forum, Anyway heres my understanding of what going on.

r1 = the end to end reading on the phase conductor on the ring
r2 = the end to end reading on the on the cpc (earth) conductor on the ring
rn = the end to end reading on the nuetral conductor on the ring

these readings should be taken at the consumer unit using a low ohms continuity tester.

so if you are not getting an end to end reading on the phase conductor you are not getting an r1 reading. which would suggest that somewhere on the ring circuit the phase coductors have seperated. (eg fallen out of the back of a socket outlet or been damaged in some way) ive also had cases where the grubb screw on the socket outlet has been screwed against the insulation and is not making contact with the copper conductor inside so look carefully. if your really unlucky the problem could be in a junction box somewhere.

The reason why you are still getting a zs reading is because the ring circuit is fed from both "legs" of the ring

hopefully you'll find it but if you don't you need to seperate the ring main and create 2 x 16 amp radial circuits.

As for the RCD protection on a TT system. You need to have a 100ma RCD time delay mainswitch But you need to make sure you also have 30ma RCD protection on the usaul circuits ie Socket outlets, showers etc. Are there RCBO's available for the consumer unit you are dealing with?

Its always worth doing all your essentail tests before working on existing circuits as well as after at least you know what your up against from the beginnig

Good luck dude.........Mutts

Mutts, probably a typo, but surely you meant create two 20A radials?

And a 30mA on a shower, when was this a requirement? (unless of course you've gone 17th, in which case you can bin the 100mA for starters.......):)
 

Had8Lives

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Arms
How are you connecting the ends of the ring at the board when you test?

Regarding the 6mm earth, I'd Code/Cat 1 it and replace with 10mm.
 
Last edited:
A

alan

  • Thread Starter Thread Starter
  • #21
I understand it is a TT system. If the main earth cable is not buried it need only be 4mm
If buried should be 16mm.

Table 10c OSG.
 
C

Cirrus

  • Thread Starter Thread Starter
  • #22
10mm standard;)
 
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