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Electrical Circuit
crisp
Posts: 435 Forumite
We have a consumer unit that is about 8 years old.
On it the downstairs sockets, lights, boiler, outside lights, upstairs sockets and lights all have a separate circuit listed on the unit.
How do i know if the downstairs socket is actually on a circuit? Are there signs or behavourial patterns to determine this?
On it the downstairs sockets, lights, boiler, outside lights, upstairs sockets and lights all have a separate circuit listed on the unit.
How do i know if the downstairs socket is actually on a circuit? Are there signs or behavourial patterns to determine this?
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Comments
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Stick a lamp in the socket, turn it on, and then turn the circuits off at the consumer unit in turn. Whichever one turns the light out is the circuit that socket is on.Adventure before Dementia!0
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apologies, maybe I should have said ring.
we had a qualified electrician over and he said that the "ring circuit for kitchen was broken" :huh:0 -
As it's a "ring" it can still work if it's broken, it's just not a ring anymore! Problem is current can only flow one way not both ways round the ring, so the wires could overheat...probably best not to have too many high power appliances on at the same time (eg kettle, washing machine, dishwasher, microwave, toaster etc) till it's sorted. Would have thought the elecrtician would have explained that?0
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I'll do my best to explain:
There are two types of circuit (for the purposes of this, anyway) - 1) Radial 2) Ring. And outlet refers to anything which uses it - so a socket, light, immersion, cooker etc.
A radial circuit is best imagined as a straight line - you have a start at the consumer unit and then it feeds one or more outlets along the line then stops. A good example of a radial circuit would be a cooker outlet, say.
A ring circuit is best imagined as a rubber band, where outlets are placed around the perimeter and it both starts and finishes at the consumer unit. The reason that in the UK (we are predominantly the only country in Europe which uses ring circuits) they are used is because for the same size/grade of cable buried in the wall as for a radial circuit, they can be loaded around 30% higher because each outlet draws from both ways around the ring at the same time, thus lowering the demand on the cable.
Therefore, if we take a typical circuit for sockets, the cable used in a house will most likely be 2.5mm (cross sectional area) per conductor - so each bit of cable has 1 x 2.5mm Live, 1 x 2.5mm Neutral and a 1.5mm Earth. I'll spare why the earth is smaller, it's a technical issue.
The maximum current (or demand) that a 2.5mm cable is allowed to deal with according to the electrical regulations (BS7671) is 27 Amps, therefore the fuse or circuit breaker needs to be 27A or below in order to protect that cable. Because no-one makes a 27A fuse or breaker then the nearest lower value is 20A. So, the maximum load on a single radial circuit (supplying sockets) is therefore 20A (roughly 5kW).
Because our ring circuit is able to function more efficiently by sharing the load around two cables, if we take our 30% figure then we get 35A for the same grade of cable - again, the nearest lower value of circuit breaker available is 32A.
Right - I hope you're still awake because without having gone through the above, then the below (which is your question!) would make no sense....
A broken ring basically means that one or more of the conductors (L, N or E) isn't making it right around our rubber band - there's a break somewhere - but we never get to know in ordinary use because the outlets still work as they are still connected back to the consumer unit, just not necessarily to each other.
Why this matters is because if you imagine we take a pair of scissors and cut our rubber band, what we have left is 2 x straight lines....in other words, 2 x radial circuits. Except, because we haven't changed anything in our consumer unit we now have 2 x radial circuits, which we established above should be protected at 20A now being fed from the same 32A protective device. Therefore, it is conceivable to inadvertently overload the cable which will lead to it overheating which is principally a fire risk, but also in the event of an electrical fault where many hundreds or thousands of amps flow for a very short time in order to trip the circuit out and make it safe if the cable is too hot then it might stop that from happening.
So, in short, it's a safety issue.
What to do about it.... well, there's two most likely causes of the break - either a loose or missed connection at the back of the outlet/s or a physical break in the cable somewhere. The former is simply a case of needing to pull each outlet off the wall and have a look, the latter can be invasive and expensive to resolve.
A decent electrician with the right test equipment will be able to find where the break is [between] fairly quickly, so that's relatively inexpensive to diagnose. If there is a damaged cable in the wall then you have three options - 1) dig it out and replace, 2) disconnect that section out of the ring at the outlets and then either 2a) downgrade the circuit breaker to a 20A (which in a kitchen could be problematic as you could get nuisance tripping due to the greater demands of all the white goods, kettles etc) or 2b) if you have a spare way in the consumer unit then have it split into 2 x 20A radials (which could in the electrical sense actually be viewed as an upgrade).
Hope that's made sense for you and helped!0 -
Good explanation. Of course, 2b) could be a downgrade if 1 of the 2 resulting radials is all of the sockets in a kitchen and the other is a single socket behind a cupboard. This would suffer the same drawback as 2a)1) dig it out and replace, 2) disconnect that section out of the ring at the outlets and then either 2a) downgrade the circuit breaker to a 20A (which in a kitchen could be problematic as you could get nuisance tripping due to the greater demands of all the white goods, kettles etc) or 2b) if you have a spare way in the consumer unit then have it split into 2 x 20A radials (which could in the electrical sense actually be viewed as an upgrade).You might as well ask the Wizard of Oz to give you a big number as pay a Credit Referencing Agency for a so-called 'credit-score'0 -
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I'll do my best to explain:
There are two types of circuit (for the purposes of this, anyway) - 1) Radial 2) Ring. And outlet refers to anything which uses it - so a socket, light, immersion, cooker etc.
A radial circuit is best imagined as a straight line - you have a start at the consumer unit and then it feeds one or more outlets along the line then stops. A good example of a radial circuit would be a cooker outlet, say.
A ring circuit is best imagined as a rubber band, where outlets are placed around the perimeter and it both starts and finishes at the consumer unit. The reason that in the UK (we are predominantly the only country in Europe which uses ring circuits) they are used is because for the same size/grade of cable buried in the wall as for a radial circuit, they can be loaded around 30% higher because each outlet draws from both ways around the ring at the same time, thus lowering the demand on the cable.
Therefore, if we take a typical circuit for sockets, the cable used in a house will most likely be 2.5mm (cross sectional area) per conductor - so each bit of cable has 1 x 2.5mm Live, 1 x 2.5mm Neutral and a 1.5mm Earth. I'll spare why the earth is smaller, it's a technical issue.
The maximum current (or demand) that a 2.5mm cable is allowed to deal with according to the electrical regulations (BS7671) is 27 Amps, therefore the fuse or circuit breaker needs to be 27A or below in order to protect that cable. Because no-one makes a 27A fuse or breaker then the nearest lower value is 20A. So, the maximum load on a single radial circuit (supplying sockets) is therefore 20A (roughly 5kW).
Because our ring circuit is able to function more efficiently by sharing the load around two cables, if we take our 30% figure then we get 35A for the same grade of cable - again, the nearest lower value of circuit breaker available is 32A.
Right - I hope you're still awake because without having gone through the above, then the below (which is your question!) would make no sense....
A broken ring basically means that one or more of the conductors (L, N or E) isn't making it right around our rubber band - there's a break somewhere - but we never get to know in ordinary use because the outlets still work as they are still connected back to the consumer unit, just not necessarily to each other.
Why this matters is because if you imagine we take a pair of scissors and cut our rubber band, what we have left is 2 x straight lines....in other words, 2 x radial circuits. Except, because we haven't changed anything in our consumer unit we now have 2 x radial circuits, which we established above should be protected at 20A now being fed from the same 32A protective device. Therefore, it is conceivable to inadvertently overload the cable which will lead to it overheating which is principally a fire risk, but also in the event of an electrical fault where many hundreds or thousands of amps flow for a very short time in order to trip the circuit out and make it safe if the cable is too hot then it might stop that from happening.
So, in short, it's a safety issue.
What to do about it.... well, there's two most likely causes of the break - either a loose or missed connection at the back of the outlet/s or a physical break in the cable somewhere. The former is simply a case of needing to pull each outlet off the wall and have a look, the latter can be invasive and expensive to resolve.
A decent electrician with the right test equipment will be able to find where the break is [between] fairly quickly, so that's relatively inexpensive to diagnose. If there is a damaged cable in the wall then you have three options - 1) dig it out and replace, 2) disconnect that section out of the ring at the outlets and then either 2a) downgrade the circuit breaker to a 20A (which in a kitchen could be problematic as you could get nuisance tripping due to the greater demands of all the white goods, kettles etc) or 2b) if you have a spare way in the consumer unit then have it split into 2 x 20A radials (which could in the electrical sense actually be viewed as an upgrade).
Hope that's made sense for you and helped!
Thank you very much for taking the time and effort to reply.
The explanation is really helpful
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Last month we had a load bearing wall removed and our kitchen rerranged.
As part of the work we had to relocate some existing sockets, cancel some sockets and add a couple of new ones.
Last week I called my own qualified electrician to inspect the work.
He pointed out a 7 faults including broken ring.
The contractors are blaming the previous electrical work for this error, however, what was tested was the electrical work left behind - touched and untouched by them but in the immediate area.
As part of the work they assured me that everything would be completed to current standard and I advised that I would be seeking an Electrical Report on the installation.
I recall it was their decision to use some of the existing wiring instead of new wiring in certain areas.
I would have thought they would have tested everything themselves before and after to avoid this exact issue.
Am I being naiive?0 -
Am I being naiive?
Not in the slightest!
It sounds to me like your builders / their electrician have messed up here big time.
BS7671:2008 Section 110.1
"[The regulations apply to.... ]"
(xx) additions and alterations to installations and also parts of the existing installation affected by an addition or alteration.
What they should have done is test the circuit before it was altered about, in which case they should be able to show you a test sheet. Save your time and breath - they won't have one. However, as per regulations 610.1 - 610.5 they should be able to produce a test sheet and an installation certificate for the work they have done (irrespective of your own inspection - and top marks for being thorough and checking!).
Of particular use to you here is 610.4 - "For an addition or alteration to an existing installation, it shall be verified that the addition or alteration complies with the Regulations and does not impair the safety of the existing installation".
Had they have tested, then it would have been instantly obvious - continuity (technically known as an "r1r2" test), which checks this, is the first one done in the sequence of tests and is also the easiest - normally takes me about 30 seconds.
I would suggest that if you have no joy in getting them to correct all faults on that circuit (which might entail some painful undoing of new work!) at their cost then you just take it straight to Trading Standards and also find what Part P scheme provider they are with (Elecsa, Napit, NICEIC are the main three) and take it up with the complaints section. Ultimately they should be insured under a guarantee of work system whereby if needs be then another contractor is instructed to put right.
Feel free to PM me for more advice - I get completely hacked off by cowboys bringing our industry into disrepute!0
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