Testing lollipop circuit

[Midwest]

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.

I'm not saying I'm right, just wondering how to test this circuit's R1+R2 as prescribed by BS7671?

 

[TJ Anderson]

I'm not saying I'm right, just wondering how to test this circuit's R1+R2 as prescribed by BS7671?

I would put R1 + R2 as a limitation in this circumstance. I would record r1, rn , r2 and Zs.

 

[Pete999]

I would put R1 + R2 as a limitation in this circumstance. I would record r1, rn , r2 and Zs.

I agree with Mr Anderson (WWE) on this one,

 

[TJ Anderson]

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?


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

Amd 3 EIC is way too long winded for single circuit mods. You could spend half hour just writing N/A!!

 

[Leesparkykent]

when I spoke to my assessor about recording the results of a hybrid/lollipop circuit he said use two lines....R1+R2 for the 6mm part of the circuit and on the other line record r1,rn,r2 and R1+R2 for the ring final part of the circuit. Obviously this doesn't help the OP as he cant access the joint....You cant record a limitation on an EIC so If this is a new circuit I would go as far to say it shouldn't of been installed with an inaccessible joint.

 

[Midwest]

Think that's the rub on this, can't access the joint, so can't properly test this hybrid/ lollipop circuit. Not sure that its a new circuit, in this case, but never the less should be properly tested before its energised?

 

[Des 56]

The joint is inaccessible,the joint was apparently made and located by a, n, other
It may be a permanent joint ! it may even be terminal screwed in a JB,he doesn't know and he can't find out,so the joint question is out of his control other than if it effects his readings

The circuit is a 6.0mm/2.5mm jointed to effectively a 5.0mm/3.0mm (2 x 2.5/1.5mm parallel ish conductors from the joint onwards)

It can be treated as a radial circuit with its minimum sizes of L + N and cpc
Size wise its a 5.0mm/2.5mm radial

I would test it as you would a 4.0mm/1.5mm standard radial, if the readings are good for that,you are well within what is required by the regs

A single R1+R2 reading at a socket will be fine for filling in the often needles boxes on the certification,thats as long as the ring has been proven to be intact in the first instance

 

[Pete999]

The joint is inaccessible,the joint was apparently made and located by a, n, other
It may be a permanent joint ! it may even be terminal screwed in a JB,he doesn't know and he can't find out,so the joint question is out of his control other than if it effects his readings

The circuit is a 6.0mm/2.5mm jointed to effectively a 5.0mm/3.0mm (2 x 2.5/1.5mm parallel ish conductors from the joint onwards)

It can be treated as a radial circuit with its minimum sizes of L + N and cpc
Size wise its a 5.0mm/2.5mm radial

I would test it as you would a 4.0mm/1.5mm standard radial, if the readings are good for that,you are well within what is required by the regs

A single R1+R2 reading at a socket will be fine for filling in the often needles boxes on the certification,thats as long as the ring has been proven to be intact in the first instance

OK so what size for the line and cpc conductors would you put on the cert? hardly 5mm because there is no such animal.

 

[Midwest]

The joint is inaccessible,the joint was apparently made and located by a, n, other
It may be a permanent joint ! it may even be terminal screwed in a JB,he doesn't know and he can't find out,so the joint question is out of his control other than if it effects his readings

The circuit is a 6.0mm/2.5mm jointed to effectively a 5.0mm/3.0mm (2 x 2.5/1.5mm parallel ish conductors from the joint onwards)

It can be treated as a radial circuit with its minimum sizes of L + N and cpc
Size wise its a 5.0mm/2.5mm radial

I would test it as you would a 4.0mm/1.5mm standard radial, if the readings are good for that,you are well within what is required by the regs

A single R1+R2 reading at a socket will be fine for filling in the often needles boxes on the certification,thats as long as the ring has been proven to be intact in the first instance

Your suppose to be telling the truth on the certificate, not making up a fairy story. A hybrid circuit consists of two very different circuit designs and should be reflected in the certificate. That way it might make things easier for the next electrician who comes along?

 

[Des 56]

OK so what size for the line and cpc conductors would you put on the cert? hardly 5mm because there is no such animal.

The circuit would be listed as 6.0/2.5 live and 2.5/1.5 Cpc
The circuit would be tested for comparison with the 4.0mm/1.5mm as I described

Your suppose to be telling the truth on the certificate, not making up a fairy story. A hybrid circuit consists of two very different circuit designs
You are supposed to relaying information that reflects the practicality of what is there,the results will then be compared to what is required
The forms have a comments box for your own fairy stories or in this case a description of the non standard circuit
The cable sizes are noted,the test results noted,the comparison with what is required can be made for the worst case scenario,that being(for those who rely on the read it by numbers on site guide) standard cable size 4.0mm/1.5mm

Tell me what you do when you take readings of an existing installation where imperial size cable is installed?
I would hazard a guess you do not check the characteristics of an obsolete 3/.029,rather you use an equivalent metric table of 1.5/1.0mm,if so,have you been spinning fairy stories as well lol

The trade has become a play it by numbers game,it would be refreshing to find electricians thinking for themselves, rather than the over reliance on guides, where in many cases the real world practical problems do not sometimes have a neat On site guide table to follow

 

[HandySparks]

A single R1+R2 reading at a socket will be fine for filling in the often needles boxes on the certification,thats as long as the ring has been proven to be intact in the first instance

Measure R1+R2 at every socket in the same way as you would for a radial circuit and use the maximum value on the cert. If there's a socket at the middle of the ring, the measurement will be the true value (assuming no spurs). If not, the socket nearest the middle will generally give a sufficiently close figure.

 

[Richard Burns]

If this is an existing circuit then Zs testing at each point would be sufficient to test the circuit, a note of the circuit construction as a 6mm² radial and 2.5mm² ring can be made and there is no need to measure R1+R2.

If it were a new circuit then the junction box would have to be accessed and made available for testing as it should not be inaccessible if required for testing.
If the junction box were available then an overall R1+R2 could be obtained by addition of the (r1+r2/4) value or the ring and the R1+R2 value of the 6mm² radial.
There is no practical method of gaining an accurate value if the junction is inaccessible.
However an estimate could be made by linking out L+E at the nearest socket to the junction box, on the disconnected ring, and measuring R1+R2 back to the CU and then estimating the length of the 2.5mm² cable run to the junction box and subtracting the theoretical value of resistance for this section.
However this all seems far too much effort (and subject to inaccuracy) unless there is a known problem on the circuit.

 

[Midwest]

Your suppose to be telling the truth on the certificate, not making up a fairy story. A hybrid circuit consists of two very different circuit designs

Tell me what you do when you take readings of an existing installation where imperial size cable is installed?
I would hazard a guess you do not check the characteristics of an obsolete 3/.029,rather you use an equivalent metric table of 1.5/1.0mm,if so,have you been spinning fairy stories as well lol

The trade has become a play it by numbers game,it would be refreshing to find electricians thinking for themselves, rather than the over reliance on guides, where in many cases the real world practical problems do not sometimes have a neat On site guide table to follow

You have a point there except when I do, I am obtaining a measurement, whereas in this case the OP can't access the joint to obtain a measurement. Apologies for the fairy stories remark, been reading far too many EU Referendum articles.

 

[7029 dave]

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.

I agree Pete, was never taught this method by my old sweats or at college or in any of my Electrical craft principles books.

 

[davesparks]

I've only ever come across a lollipop circuit used where an isolating switch is required for the whole circuit. So a 6mm twin was run to a DP switch and a ring taken from the dead side of the switch. This was in recording studios and classrooms where the layout of the sockets was pretty much a circle around the room so suited a ring circuit.

 

[Dan Brown]

Well thank you everyone for your input so many helpfull people on here

 

[Had8Lives]

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.

The danger with testing end to end at a socket is you never know if a wire has fallen out of a terminal when you refit the socket. I always test end to end at the consumer unit.

 

[davesparks]

The danger with testing end to end at a socket is you never know if a wire has fallen out of a terminal when you refit the socket. I always test end to end at the consumer unit.

If you can't tighten a terminal screw properly then you shouldn't be doing the job in the first place.

 

[westward10]

I've only ever come across a lollipop circuit used where an isolating switch is required for the whole circuit. So a 6mm twin was run to a DP switch and a ring taken from the dead side of the switch. This was in recording studios and classrooms where the layout of the sockets was pretty much a circle around the room so suited a ring circuit.

This is common practice in schools so teacher can have control over the sockets. Me, if you cannot trace where the 6.0 becomes a possible RF I would put a 20A device in because you have no way of knowing how it is configured and as previously stated it may reduce in csa before it becomes a RF anyway.