Testing lollipop circuit

[Dan Brown]

Just wondering how to go about testing continity on a lollipop circuit, radial to ring. But no access to junction box (not my fault), obviosly there are only one set of twin earth at the breaker, which was 40amp and I downgraded it to a 32amp because I didn't think it was safe to have the 40 who ever did this must of not thought about it.

It's 2.5 ring
6mm radial

 

[telectrix]

IR test as normal. get your Zs readings at sockets, record highest. the downsizing to 32A is correct, as you need to fit OCPD to heve a lower In than the Iz of the smallest cable/s, so that's the 2.5mm "ring" on the circuit. make note in comments.

 

[hightower]

You can always carry out an end-to-end behind any socket on the ring. Good tip I picked up not so long back to save opening the consumer unit.

 

[Midwest]

Seem to remember reading somewhere, that the individual circuits, radial part & RFC part should be tested separately and the results recorded separately on a cert'; which because of the nature of recording the test results would have to be an EIC. That is, the R1+R2 values for the radial and loop values for the RFC?

PS, which is going to be difficult if you can't access the JB.

 

[hightower]

Elecsa offer a cert for up to 3 circuits on minor works - couldn't this be used?

 

[Midwest]

Elecsa offer a cert for up to 3 circuits on minor works - couldn't this be used?

Not with their electronic certs, cheeky monkeys! Mind you same price, just a bit more form filling.

 

[TJ Anderson]

Seem to remember reading somewhere, that the individual circuits, radial part & RFC part should be tested separately and the results recorded separately on a cert'; which because of the nature of recording the test results would have to be an EIC. That is, the R1+R2 values for the radial and loop values for the RFC?

PS, which is going to be difficult if you can't access the JB.

You would not need to do that, it would not acheive anything other than burning time. Although not standard practice, at the end of the day, It is still one circuit and should just be recorded as such. The Zs recorded would just be the highest value at a socket as usual. Note on minor works that there is a 6mm2 cable jointed to 2.5mm ring final and that junction is inaccessible.

 

[bigspark17]

i woul say an end to end test at the back of one socket outlet is essential here, otherwise there could well be 32A radial on 2.5mm t&e. I would also add i agree with you downgrading from 40-32 mcb is a good move but you shouldnt have done before confirming the ring otherwise it could need a 20A mcb

 

[Midwest]

You would not need to do that, it would not acheive anything other than burning time. Although not standard practice, at the end of the day, It is still one circuit and should just be recorded as such. The Zs recorded would just be the highest value at a socket as usual. Note on minor works that there is a 6mm2 cable jointed to 2.5mm ring final and that junction is inaccessible.

Not sure your right, but then again neither am I.

This is what I'm thinking; It is not just one circuit, it's a hyrbrid circuit. Certainly the RFC part of the circuit would be need to be tested insequence as normal, to establish if it is installed and connected correctly. This can be achived without access to where the circuits join, if the radial circuit is isolated at the supply. But there is no method of accurately confirming the measurement of the radial cpc R1+R2 or R2, without access to the joint?
Hence the reason for the testing & recording the two circuits separately.

 

[Pete999]

You would not need to do that, it would not acheive anything other than burning time. Although not standard practice, at the end of the day, It is still one circuit and should just be recorded as such. The Zs recorded would just be the highest value at a socket as usual. Note on minor works that there is a 6mm2 cable jointed to 2.5mm ring final and that junction is inaccessible.

TJ not sure where the Minor works certificate come into play on this post,

 

[TJ Anderson]

TJ not sure where the Minor works certificate come into play on this post,

My thinking was he has modified a single by changing OCPD from 40A to 32A so he should certify it.

 

[Pete999]

My thinking was he has modified a single by changing OCPD from 40A to 32A so he should certify it.

OK good point

 

[Midwest]

My thinking was he has modified a single by changing OCPD from 40A to 32A so he should certify it.

Not sure if that's a like for like replacement?

 

[TJ Anderson]

Not sure your right, but then again neither am I.

This is what I'm thinking; It is not just one circuit, it's a hyrbrid circuit. Certainly the RFC part of the circuit would be need to be tested insequence as normal, to establish if it is installed and connected correctly. This can be achived without access to where the circuits join, if the radial circuit is isolated at the supply. But there is no method of accurately confirming the measurement of the radial cpc R1+R2 or R2, without access to the joint?
Hence the reason for the testing & recording the two circuits separately.

I do see where you are coming from and I am not saying I am right either. The way I see it though is it is just another termination on the same circuit and the ring can still be proved from end to end testing at a socket outlet. We still still modify other circuits where we know they must have junctions but we can't access them and we just go on our test results which all we can reasonably do sometimes.

 

[TJ Anderson]

Not sure if that's a like for like replacement?

No, definately not, because it is a different rating MCB with different max Zs. It needs to be certified as compliant (Officially obviously ☺, in reality..... that prob won't happen! )

 

[SJD]

With one MCB (or RCBO), it is one circuit, it just happens to have a non-standard wiring arrangement.

Summary, you need to be testing / checking (a) the conductor details are compatible with the overcurrent device, (b) earth continuity at each outlet, (c) polarity at each outlet, (d) Zs is within limits, plus (e) IR tests, and (f) RCD tests if applicable.

If you can prove the 2.5mm2 cable is wired as a ring, and it is directly on the end of a 6mm2 radial, then that should be sufficient for (a). However, not being able to access the join, you are assuming this is the case. I did once find a lollipop ring where the 6mm2 was first extended by a few metres in a single 2.5mm2, and only then became a ring, it was only found because I was looking under the floorboards prior to other work, I'd have never noticed in a standard test & inspection. [It was an old cooker circuit repurposed for some kitchen sockets.]

The rest of the tests should be straightforward.

 

[Midwest]

I do see where you are coming from and I am not saying I am right either. The way I see it though is it is just another termination on the same circuit and the ring can still be proved from end to end testing at a socket outlet. We still still modify other circuits where we know they must have junctions but we can't access them and we just go on our test results which all we can reasonably do sometimes.

Just cant see how you can get a R1+R2 for the circuit, when one doesn't included the other? You'll be measuring R1+R2 for the RFC part of the circuit, but not the radial, unless you can access the joint, and obtain a separate R1+R2 or R2 for the radial?

No, definately not, because it is a different rating MCB with different max Zs. It needs to be certified as compliant (Officially obviously ☺, in reality..... that prob won't happen! )

I was always under the impression that using a Minor Works cert' for a change of ocpd with different characteristics, was inappropriate?

 

[Pete999]

Seem to remember reading somewhere, that the individual circuits, radial part & RFC part should be tested separately and the results recorded separately on a cert'; which because of the nature of recording the test results would have to be an EIC. That is, the R1+R2 values for the radial and loop values for the RFC?

PS, which is going to be difficult if you can't access the JB.

Regardless of how you test this circuit, it's still only one circuit, and therefor be treated as such, personally I hate Lollypop circuits, it's a Devil's concoction, as can be seen in this thread, I'm not even sure if it's a recognised method, others will, I'm sure, disagree with me, maybe that because I was raised ding things the proper way, go on have a dig, water off a Duck's back.

 

[bigspark17]

Not sure your right, but then again neither am I.

This is what I'm thinking; It is not just one circuit, it's a hyrbrid circuit. Certainly the RFC part of the circuit would be need to be tested insequence as normal, to establish if it is installed and connected correctly. This can be achived without access to where the circuits join, if the radial circuit is isolated at the supply. But there is no method of accurately confirming the measurement of the radial cpc R1+R2 or R2, without access to the joint?
Hence the reason for the testing & recording the two circuits separately.

Hi midwest, you seem to be contredicting yourself here, you want two set of test results but OP cleary posted joint not accessible so thats impossible. There is one set of results for the one ocpd in this scenario imo, the weak part of the circuit on a 32A mcb would be the 2.5mm so if all conductors are a complete ring end to end in the circuit and zs values at each socket outlet are ok then imo the circuit would be ok for continued use under a eicr, if the 6mm wasnt in a satisfactory condition this would show through to the 2.5 ring. IR tests can commence the same,though i would suggest a comment about circuit on cert and i eould never extend a ring with a 6mm to mains myself though have come accross it.

 

[Pete999]

Just wondering how to go about testing continity on a lollipop circuit, radial to ring. But no access to junction box (not my fault), obviosly there are only one set of twin earth at the breaker, which was 40amp and I downgraded it to a 32amp because I didn't think it was safe to have the 40 who ever did this must of not thought about it.

It's 2.5 ring
6mm radial

Dan what was the reason of your visit to this property, was it to carry out an EICR? if so then surely you test the installation, code it to what you think it should be coded, note the deviations from BS 7671, give the cert to the person ordering the work, point out verbally, any major concerns you have, and the possible dangers therein, and let them make the decision, as to to what extent they want you to rectify any faults or deviations, give them your invoice and Bob's Yer Uncle off you go.