Urgent Electric Problem

Came back from the pub quiz last night to find the downstairs in darkness.
The RCD had tripped. It would not reset unless we had all the light switches off.
The lights are on a 6A RCBO with an 80A 30mA RCD
Strangely though we found out that I can have a small number of lights on, but beyond that point, the RCD or RCBO goes. It doesn't like fluorescents, they will trip every time, yet 5 incandescents on a dimmer in the front room are OK. Although some of the lights that will stay on are are energy savers (so fluorescents!)
The Megger shows live earth and live neutral OK! (With all light switches turned off - so is it a fitting?)
This has me puzzled.
Any thoughts?
Cheers
Peter

puffernutter wrote:
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Right, it's a Neutral Earth short - just got to find it!
Cheers
Peter

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Strange - in that case, why would it depend on whether the light switch(es) were on or off ?

puffernutter wrote:
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That suggests that some of your light switches are switching the neutral? or is that you have a neutral earth leak that is insufficient to trigger the trip as well as some other leakage path which is switched in by some of your lights. Have you got enough real lamps to use for now in place of the crap CFLs. Might buy you some peace and quiet over the festering season!!
Good luck
Bob

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Start with any outside lights or any fittings that you have recently fitted or changed lamps in.
Adam

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have you hung any pictures or anything on the wall in the last few days and may be caught a wire under the surface?
switch your lights on one at a time to try and narrow down the fault
good luck

Bob wrote:
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An interesting one, not least for the totally illogical way that the previous owner had wired it! (He was a builder, so I should have expected it I suppose!)
I live in an 1890s terrace. From front to back we have 2 lights in the hall, one in the living room, two in the dining room, one in the kitchen, one in the utility room one in the cloakroom and one outside.
With the Megger I quickly established that the back of the house (from the kitchen was OK). I had to get most of the upstairs bathroom and landing floors up to work out the feed from the fusebox goes to the living room first (5 incandescents on a dimmer and worked fine) then to the dining room (one three arm fitting that only worked with one energy saver fitted) a double fitting that tripped with anything in) then splits back to the hall and forward to the kitchen etc.
To cut a long story short and after about 4 hours of testing (removing wires, Meggering etc.) it turned out to be an overheated chocolate block (poor connection?) in the three arm fitting in the dining room that was shorting earth/neutral (yes the one that was working!) and once that repaired, all was OK)
What a sod to find though, not helped by the fact it "seemed" OK!
Anyway all sorted and a Happy Christmas to all on UK DIY
Cheers
Peter

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HI,
I'm in the US and it sounds like you're in the UK or some other European country so I know our wiring is different, but ... maybe you can clarify my confusion in this post; always interested in things different from my own situation<G>.
I fail to see how a neutral/earth short could cause any visible problems. Depending on resistances back to the electrical panel, they should simply share the neutral current, or if the resistances are different, the lowest resistance path would carry the current back to the panel. Normally Earth leads should carry zero current.
I suspect my confusion is due to things like "The lights are on a 6A RCBO with an 80A 30mA RCD", which are absolutely meaningless to this yank<g>! So apparently the key words you're using are not ckt breakers, but some other form of protection that relies on other than simple current overloads; right?
Hmm, I may have worked it out. Google was no help with its gazillion hits of Roman Catholic ... , but Wikipedia seems to have filled in the blanks! And here I thought I understood your ring ckts and all that! lol.
I know for instance that RCBO = Residual Current Circuit Breaker with Overcurrent Protection. THAT sounds like a ckt breaker but Residual Current fits in there how?
Wikipedia seems to indicate that RCD stands for "Residual Current Circuit Breaker "; is that right? Now that sounds like what we might call a GFCI or Ground Fault Ckt Interruptor, a product that keeps a measure of the current in the hot and neutral lines and if they vary by more than a few milliamps, opens the ckt., assuming there is a fault at some point. Would RCBO be the same thing, the only difference between the two being that one is located at the point of use, and the other at the Mains electrical panel?
Thanks for any clarification anyone is willing to provide,
Twayne`

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RCD's, or Residual Current Devices (fomerly known as earth leakage circuit breakers,) are very common in 240V areas. Remember much of your electrical supply is 110V - sometimes even 55-0-55 - with 240V across phases used for higher power equipment. In Europe we use a (nominal) 230V single phase supply for everything - nominal because we are supposed to be standardised across the EU. In practice Europe mainly uses 220V and the UK and Ireland use 240V but both fall within the permitted tolerances on 230V.
In the UK domestically we use a single phase supply which is usually single pole switched and carries a small cartridge fuse in the plug to protect the cable and appliance. The plug is three-pin with earth, although the earth spike may not be local. It has to be said that most domestic electrical kit - brown goods such as hi-fi and TV, portables such as hairdriers and shavers, and many electrical tools such as drills - are these days fitted with two-core cable and are double insulated with a double pole switch. This is because there is no polarity awareness in most of the EU - they often use two-pin Schuko plugs which can be reversed on insertion. IME even if the outlet has an earth pin - as often found in France - there is still no standard wiring for the polarity of the other two pins. This is a problem if three-pin weatherproof connectors are used - which are supposedly standard across Europe (we know them as BS4343 in the UK) - which we use with our touring caravan: they are clearly polarity marked on the body but I have only experienced three (out of many) sites correctly wired. I often wonder if they are even earthed!
A RCD is basically a pick-up coil through which the L and N cables both run. If the current through both cables is the same then there will be nothing induced in the pickup coil. If there is a current imbalance - some is flowing through you - then there will be a current imbalance in the main cables which the pickup coil will detect and trip the supply. Normally that current difference is 30mA, but for 'at risk' places such as an electronics work bench 10mA is often used. It is usual for the RCD to be on the main supply - it is often also the main supply switch as it is double pole - so if it is tripped everything goes off, not just the one circuit. More modern installations have split rings so that wired-in appliances and lighting are not protected and you don't get plunged into darkness for a simple electrical fault.
Incidently, if you wonder why our electrical outlets are such it is a historical cost thing. Most European wiring is radial - i.e. every outlet has it's own cable back to the supply board and is individually fused (or breaker) and some places (such as Germany) have outlets that are mechanically slightly different and are supplied at 6A rather than the 'normal' 16A. British and Irish wiring is almost always in a ring so the ring is fused or switched at 30A or 32A but the plug carries a fuse which may be 1/2/3/5/7/10/13A, although the Great British Public, being generally thick and unknowing, use moastly 3A or 13A.
Hope that clears your understanding?

Woody wrote:
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Woody,
You gave a rather good answer right up until your "the Great British Public, being generally thick and unknowing, use moastly (sic) 3A or 13A).
Does that make you the only intelligent Brit out of 65,000,000 or so then?
I think not, and I would be interested how you have managed to come to that conclusion without inspection every piece of domestic electrical equipment in the country
Unbeliever

Unbeliever wrote:
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Amendment!
My last paragraph should have read:
I think not, and I would be interested how you have managed to come to that conclusion without *INSPECTING* every piece of domestic electrical equipment in the country.
Unbeliever

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Simples.
Have you ever seen any equipment on sale or tried to buy a plug retail with anything other than a 3A or a 13A fuse? Equally have you ever tried to buy fuses retail other than 3A or 13A? Ergo most (non-understanding) people will use 3A or 13A fuses as they either know no better or don't have the knowledge to go buy something else.
From a personal standpoint I tend to use 2A and 5A fuses as, IME, 3A fuses - especially on portable equipments - seem to have mechanical problems. Drop the plug and the fuse fails mechanically, but 2A and 5A don't.

wrote in message>>>
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3A and 13A fuses are perfectly suitable standard fuses for all new equipment. An appliance takes one or the other depending upon it's power rating.
And you do know that you should not put a 1A fuse into a plug don't you?
Adam

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Yes, I am an engineer by education and experience and we used to design product for the UK and EU countries. We're NA. I'm retired now for health reasons, but I remember being surprised the first time I came across the plug fuses. I was also surprised to discover that most equipment was sold sans power cords; it was up to the user to get those. This experience was gained as manager for a telecom compliance testing laboratory. We served NA, Europe, UK and the Pac Rim down to Australia. Every country would be similar "except" and it used to be "interesting" keeping them straight<g>.
...
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It's the same here in NA in some places, especially w/r to the earth. Hot and neutral have to be right though or you won't pass inspection. That doesn't stop the do it yourselfers from doing their own work, though, without regard to polairty. Here only generators would be often miswired, even often use multi-branches with a common neutral to make wiring easier. Some bands love the miswires because they're sure their amps are working when they hear that hum<G>>
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Ah, we'd call that whole-house protection over here. I never thought about what their trips might be current-wise. They're fairly new over the last few years. Then we also have arc-fault-interruptors; should an arc occur anywhere, even without being able to ever pop the breakers, they'll open. I haven't installed any yet but plan to - arcs are what start fires.
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That's news to me. I didn't know the individual ring ckts were fused or switched. It sort of makes me shudder to think about trying to locate a ring ckt's fuse or switch.
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Thanks for the response; we seldom got near the actual bldg wiring in my business unless we had to figure out an earth or neutral problem that screwed up a PBX. We had a plant for R&D and Repair in Wales and I always loved having to make a trip over there. Well, except for that long, boring trip across the pond, that is! I never got anywhere other than Wales for sightseeing and a couple trips into London some evenings, but I loved it.
Regards,
Twayne

Twayne wrote:
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You have spotted the name of this group I trust?
Andy

In typed:
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Yup; but occasionally some things tend to get lost in my case I guess<G>. I enjoy this group and often read it but don't post very often. Mae culpa.
Twayne

Twayne wrote:
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Twayne,
A question about US installations from an interested UK reader.
If you have 3 phase power installed into a property in the US, do you get three lots of 220/110 v split phase supplies eg 110v 3phase as well as 220v 3 phase?
Or how does it installed if not?
Second question How do US power consumption meters work for 110v and 220 v split phase? or do you have two meters in the home?
TIA
Bob

In typed:
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Oof! That's a tricky one because there are several different kinds of wye and delta arrangements for 3-phase power. You can get 120, 208, 220, 240, 360 and 480 and sometimes higher voltages for specialized industries. You'll never find any of these wye or delta arrangements in the home though. Probably the easiest way to answer is to provide a link or two. Also, these would never be found in a residence. Residential is always single-phase, split-phases into the home with 110Vac per leg,or 220Vac between the split (xfmr is center tapped for neutral and that's bonded to earth with an electrode driven into the ground).
http://www.elec-toolbox.com/usefulinfo/xfmr-3ph.htm
http://en.wikipedia.org/wiki/Three-phase_electric_power
http://www.tpub.com/content/construction/14026/css/14026_245.htm
http://mysite.du.edu/~jcalvert/tech/threeph.htm
http://www.mikeholt.com/mojonewsarchive/EC -
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lol, that depends too! Yes every home or apartment has its own electric meter. I said it depends because the old analog meters are presently being switched out in favor of newer digital meters which can provide a lot more information. To read the digital meters, they only need to drive by in their vehicles and which then transmits the address and power usage details to them. The transmissions are even encrypted.
I'm sure they probably all work as in the UK, measuring kilowatt-hours. With a residence, there is no accounting for power factor of course; you take what it measures<g>. In reality it gets explained iike it would make little difference, but from some of the electric motor (furnace, fans, etc) power factors that run for long periods of time that I see in my own house, I'm not so sure it's negligible!
Power from the grid, high voltage, is connected to the grid's transformer. This is a center-tapped transformer, which converts the single-phase input voltate into split-phase ( two 120Vac outputs w/r to the centertap (which is neutral/earth and bonded at the pole)). So coming TO the house from the transformer are three wires: The two out of phase hots, and neutral. Once in the meter, there is no ground nameing any longer since earth ground for the house is derived from a separate electrode driven into the ground. From the meter, the two hots go into the Mains panel Mains Breakers or Fuses along with the third wire, which connects to the Earth bar within the panel and which all internal ckts return their earth grounds to. Earth and Neutral are only allowed to be tied together within the Mains panel and nowhere else unless a special exception is claimed. Where the breakers hang, there are two busbars giving every other breaker the opposite phase of 120Vac. So to get 240Vac, you use a "ganged" double breaker where two adjacent buses are connected. Thus, the difference between the output side of breaker to breaker then will measure 240Vac since they are out of phase. A LOT of people like to mislabel this as 2-phase power, but that's wrong: It's called split-phase. One phase is split via the centertapped transformer providing the power from the grid. In most cases people don't care, but don't call it two phase when you're talking to anyone in the business or who is a little egotistical<G>. Thus, residences are only equipped with 120 or 240 @ 60 Hz in the US and Canada. The 240Vac only gets used for major appliances such as our well pump, clothes drier, water heaters, things that otherwise would require very large, heavy cabling. Lights and all normal receptacle in the living areas are almost exclusively 120Vac. In 240Vac install, the Neutral isn't used though there are exceptions. Earth is always connected to anything that's not class II design.
In the event I haven't put you to sleep, which I know my verbosity has a habit of doing to people, you might check out Mike Holt's site if you'd like some good, down to earth definitions and descriptions of the many different variables that are possible. I highly recommend him and it's a "safe" site, pushing nothing nefarious or covertly.
http://www.mikeholt.com/technical.php?id=technicalgeneral
Hmm, looks like he's made the forums major, too; http://forums.mikeholt.com/archive/index.php/t-68677.html It's been a long time since I visited his site.
And here's a popular product here in the US; don't know if they make other localized product. "Kill-a-watt meter". http://michaelbluejay.com/electricity/measure.html
I bet that's all clear as mud, huh? I tried!
Twayne
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120 ----------- ---------Mains Sw ---------Breakers Buss 120Vac to Neutral meter 240Vac Hot to Hot 120 ----------- ----------Mains Sw----------Breakers Buss 120Vac to Neutral
Neutral -----------------------------------------Bonded to Mains breaker panel

Twayne wrote:
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Hi Twayne,
I'm with you so far and i understand the difference between 2 phase and split phase. Returning to my questions though.... Meter question.
How does one meter measure the power pulled from both legs of the split phase supply?
THREE phase question.
If a property has THREE phase power installed do they get all three 110v phases with respect to neutral as well as all three 220v phases?
Bob

In typed:
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Hmm, I think the wikipedia link touched on that; it's just measuring the VA (kWH) of both hot leads. More power makes the meter click faster, basically. The site "How Stuff Works" might have something for you in more detail. I don't pretend to know the cktry inside a meter but it seems to be rather simple. It's not meter design, which I don't seem to be able to find quickly, but it may help too: http://electrical.about.com/od/panelsdistribution/qt/electricmetermeasurements.htm
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No. IME anyway, the phases are all 120 Vac but each is slightly out of phase (but not 180 degrees) from each other. A 208V ac system is shown here, comprised of the three 120Vac phases: http://www.allaboutcircuits.com/vol_2/chpt_10/2.html
As for 220, remember, our systems are different than yours. 240 (here) is "built" from two 120V lines from a center-tapped xfmr, being called 'split phase' since the phase shifting is done via the xfmr on the pole. There are several WYE and DELTA situations which, again, are easy to look up on Google or your favorite search engine. This is an advertisement, but with good information, all based on 220Vac sourced from 120V: http://www.spadepot.com/spacyclopedia/wiring-hot-tub-spa.htm
In industrial buildings, you'll often find humongous wires coming from the xfmr to a quick disconnect and then splitting off to several panels, each panel meant for a separate part of the plant, and within those, heavier panels for the hi-curent equipment. Somewhere in the mix will be large capacitor banks used to correct for power factor and the meters are usually in that same vicinity IME. That's a generality of course, and things vary, but ... that's the gist of it.
I trust that helps a little. It's hard to explain some parts of these things without writing a book that duplicates what's already been written, which is why I use the links for references. You might want to look a tad further into some of the original links I provided you too; occasionally the meat of the info isn't onscreen when you open the page.
HTH,
Twayne
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