Ring final end to end test

[Maxstone89]

As doing a cu change ,I have a ring final in a house with an end to end reading on r1-r2-Rn are so low that somewhere very close under a floorboard the ring must have been connected together somewhere, customer refused to pay more, so i have put in a 20amp mcb. To comply with current rating of a 2.5mm cable for a radial circuit,

What would you have done.

Regards Kurtis Randle

 

[Leesparkykent]

As doing a cu change ,I have a ring final in a house with an end to end reading on r1-r2-Rn are so low that somewhere very close under a floorboard the ring must have been connected together somewhere, customer refused to pay more, so i have put in a 20amp mcb. To comply with current rating of a 2.5mm cable for a radial circuit,

What would you have done.

Regards Kurtis Randle

Did you test to see if the there was a bridge connection anywhere?

 

[Maxstone89]

It was end of day and they didn't want to pay for anymore, just said make it safe, i had briefly done some tests but didn't have much time, so guessing it was in a junction box. Is changing to a 20a mcb okay. Its safer than before i know that

 

[7029 dave]

As stated, could be an interconnection on circuit.

 

[Maxstone89]

Had thought that but what would people do to make safe, would you down rate to 20a mcb and divide the to ends into 2 x 20a radial circuits ?

 

[Simonslimline]

Carry out the full 3 stage test for a RFC perhaps and locate where the problem lies. JMO though.

 

[Deleted member 9648]

As doing a cu change ,I have a ring final in a house with an end to end reading on r1-r2-Rn are so low that somewhere very close under a floorboard the ring must have been connected together somewhere, customer refused to pay more, so i have put in a 20amp mcb. To comply with current rating of a 2.5mm cable for a radial circuit,

What would you have done.

Regards Kurtis Randle

I think you made a good call. Personally I think testing and verifying RFC's which are an unknown quantity is often very difficult within a reasonable timeframe and without excessive disruption. Verifying spurs from spurs etc and inconsistent continuity readings may well be beyond the scope of what it is reasonable to carry out for a CU change.Note on your EIC that the ring requires further testing because of unexpected readings and that until the ring is properly verified the rating of the OCPD has been reduced to ensure safe operation. --- covered.

 

[Deleted member 9648]

Carry out the full 3 stage test for a RFC perhaps and locate where the problem lies. JMO though.

Time consuming and as the client has stated he wont pay any more the OP will be carrying out voluntary charity work.

 

[Maxstone89]

I think you made a good call. Personally I think testing and verifying RFC's which are an unknown quantity is often very difficult within a reasonable timeframe and without excessive disruption. Verifying spurs from spurs etc and inconsistent continuity readings may well be beyond the scope of what it is reasonable to carry out for a CU change.Note on your EIC that the ring requires further testing because of unexpected readings and that until the ring is properly verified the rating of the OCPD has been reduced to ensure safe operation. --- covered.

Agree, as if the customer wont pay all that can be done is to make as safe as poss in timeframe and cover --- in EIC by noting it down and inform customer.

 

[Dave OCD]

Just out of interest Kurtis, could you post the actual readings ?

 

[Maxstone89]

About 0.14 for r1 and rn cant remember what r2 was from top of my head.

 

[Eddiesparks]

Probably about 0.2388 if my calculations are correct!

 

[Pete999]

As doing a cu change ,I have a ring final in a house with an end to end reading on r1-r2-Rn are so low that somewhere very close under a floorboard the ring must have been connected together somewhere, customer refused to pay more, so i have put in a 20amp mcb. To comply with current rating of a 2.5mm cable for a radial circuit,

What would you have done.

Regards Kurtis Randle

Was the testing carried out prior to the CU change?

 

[SJD]

Is this an old house, e.g. 1960's? Sometimes the RFC is wired so all the socket drops are spurs from junction boxes (under floor or in ceiling) connected off what is then electrically quite a short ring. Then for a single floor, r1=0.14 could be quite a reasonable value.

 

[Jamie Parry]

Like someone has mentioned i would put it on a 20A braker suitable for 2.5 job done.