View Full Version : Any electricians in the house?

Shaggy Sheep Driver
20th Feb 2015, 13:04
Last night at about 04:30 am our house power went off. Investigating this morning I discovered that the main circuit breaker had tripped. On resetting it, all was well.

But - each circuit in the house has its own CB. None of these had tripped. Only the 'master' CB which powers all the others. How could this happen? Surely whatever caused the event should have tripped the CB on that circuit. I can see it might also trip the 'master' CB, but I can't see how the 'master' can trip yet the individual circuit CBs remain untripped.

Can anyone advise how this might happen?

20th Feb 2015, 13:06
I shall follow this with interest as the same happens to my house electrics.

20th Feb 2015, 13:08
A power surge from the juice coming into your home ala the electrical company. This is probably the most likely explanation for this. :ok:

20th Feb 2015, 13:10
I have known the master CB to be triggered when lightning is in the vicinity leaving the individual circuits unaffected.

Shaggy Sheep Driver
20th Feb 2015, 13:23
So the master CB can be tripped by events on the incoming mains. makes sense.Thanks!

20th Feb 2015, 13:23
SSD - it is possible that the combined load on the main c.b. was enough to trip it but none of the individual c.b's were loaded excessively.Did it occur when the central heating was due to come on? The surge when the pump started might have just been enough to cause the problem.

20th Feb 2015, 13:30
Master trip means a problem on the main power supply.

I am presuming you have no appliance switching on at 4:30am which might need checking, which may have overloaded the system.

Possibilities include:
mains power surge (e.g. lightning)
loose connection upstream of the main CB (was it windy that night?)
failing master CB (how old is it?)
short circuit not protected by a CB (i.e. some non-standard wiring somewhere)

This is one thing I would shell out for a qualified electrician to check. If it's a failing main CB or loose connection, it's probably quite cheap to fix.

Your choice as to whether you leave it to see if it was a one-off or it happens again. I would definitely check after a second trip.

n.b. I have an engineering degree and designed my own house electrical system (which passed Inspection!), but I'm not a qualified electrician.

20th Feb 2015, 13:38

All valid possibilities sir. However, from my own experience (short-lived as a Lineman for a power company way back when) most often a power surge on the main line will trip main breakers in homes. Said power surge can be caused by several factors, lightning strike being one of them. Other factors include: faulty transformer upstream, rolling power brownouts not handled correctly by the power utility, etc.

But, like Fox3 wrote, if you experience another main breaker trip I would definitely have it looked at my a certified electrician.

20th Feb 2015, 13:41
when you say main circuit breaker, do you mean the RCD or the big red switch, if it was the RCD that means there was a leak to earth somewhere, the smaller circuit breakers will only trip with excessive load, not an earth fault.

20th Feb 2015, 13:42
The difficulty in analysing an intermittent fault (whether it be an electrical system or a mechanical system) is that the investigator has to guess what the fault might have been.

20th Feb 2015, 13:46
Thanks Sgt Rock.
It would seem the UK power grid isn't in the best of shape anyway.
British power station flunks the test | Datacenter Dynamics (http://www.datacenterdynamics.com/focus/archive/2014/11/british-power-station-flunks-test)

Last time I had some main panel work done in the UK (2007), the power company electrician informed me off the record that several problems like brownouts and overvoltages on circuits which were reported were solved by swapping the poor connection to another customer and hoping they didn't complain.

Shaggy Sheep Driver
20th Feb 2015, 13:58
It wasn't the big red one on the input. Isn't that just an isolating switch? It was the master CB that feeds all the subsidiary CBs. I thought all the CBs, master and subsidiaries, were RCDs? Is that not the case?

Nothing in the house was timed to switch on at that time.

The distribution panel was installed about 3 years ago. Before that we had the old wire fuses!

It hasn't happened before. All that has happened before is the occasional tripping of the CB feeding the kitchen lights on failure of one of the ceiling lights.

If it happens again, I'll get the electrician in to check it, but for now I'll assume it was caused by an event on the incoming mains.

20th Feb 2015, 14:11
I thought all the CBs, master and subsidiaries, were RCDs? Is that not the case?

I believe not. You should be able to check which CBs are RCDs by looking at them. Last couple of places I had in the UK had an RCD-protected section of the board and a non-RCD section.
If done 3 years ago, yours should meet 17th Edition rules which means almost all RCD-protection (alarms may not be).

Good quick summary (with pix) here
AA Electrical Services - do you need a new fuseboard or consumer unit (http://aaelectricalservices.co.uk/consumer_unit.html)

20th Feb 2015, 14:26

My first thought would be to check the ratings of the sub-circuit breakers and the main CB.

As was mentioned earlier could be that the potential load of the house's sub-CBs is greater than the main CB.

Is your house rural or urban? If latter then highly unlikely to be an external line problem but not unheard of.

Shaggy Sheep Driver
20th Feb 2015, 14:36
We are 'semi rural'. On very windy days, the lights sometimes dim or flicker! There must be overhead lines somewhere in our supply chain! I'm going for line supply event unless it happens a few more times (never happened before in the 3 years the panel has been in).

Unlikely to be cumulative load on the master CB in the early hours - not much in the house is drawing current then.

20th Feb 2015, 14:40

There are overhead lines in everyone's supply chain. :ok::E

Shaggy Sheep Driver
20th Feb 2015, 14:43
True, but not everyone's lights flicker on windy days!

20th Feb 2015, 15:30
I'd like to know why SSD waited until this morning to investigate why the power went out at 4.30am the night before...

20th Feb 2015, 15:36
airship? WTF? 04:30 IS this morning.

20th Feb 2015, 15:40
General, his exact words were: Last night at about 04:30 am our house power went off. Investigating this morning I discovered...

You're being spikeful! Get down to earth!

20th Feb 2015, 15:44
Oh airship, don't be so pedantic. People do refer to early morning hours as "last night." I seriously doubt SSD left it a full day to investigate.

Back to Mars with you boy. :}

20th Feb 2015, 15:51

If it is dark it is night. Simples

20th Feb 2015, 15:52
I just thought that SSD might have been doing something else he didn't wish to interrupt at 4.30am. Even something naughty. You're the one making a faulty connection. Please check your circuit-breakers...

20th Feb 2015, 15:52

Cheap lightshades is the cause of light flicker

20th Feb 2015, 15:57
Another plausible reason for flickering bulbs:


Shaggy Sheep Driver
20th Feb 2015, 16:06
At 04:30 today I was sound asleep. Mrs SSD woke me at 07:30 to fix the power problem. 07:30 is as bad a time to have to get up as 04:30 when you're nicely retired!

Flickering lights - I remember those flickery bulbs in 1950s pubs! The same pubs that had table lamps with shades decorated with a painting of Ye Olde Coaching Inne, with the windows cut out so the light shone through. How twee!

20th Feb 2015, 16:13
I have it from a reliable source, that UFO activity is/was/and still is, in abundance over the time frame. Don't let the bas***rds probe you.

20th Feb 2015, 16:18
dazdaz1 wrote:

Don't let the bas***rds probe you.

Brain suck. :}

Shaggy Sheep Driver
20th Feb 2015, 16:21
I hear Millipede went for a brain scan recently, but they found nothing. :}

20th Feb 2015, 16:21
How did you know it was at 0430 if you were asleep?

Shaggy Sheep Driver
20th Feb 2015, 16:22
How did you know it was at 0430 if you were asleep?

How do you think? Go on, guess... it's not 'ard!

20th Feb 2015, 16:24
Maybe the clock cause the power surge.

20th Feb 2015, 16:25
What was Mrs. SSD doing up at 4.30am to notice that the power was out?

20th Feb 2015, 16:27
Do pay attention 007 "How did you know it was at 0430 if you were asleep?"

because he was awake at 0430

20th Feb 2015, 16:28
Wow, lots of Einsteins here today. :}

20th Feb 2015, 16:30
Although Spanish wiring is not the same I have an interest in this. As far as I can see it has not been established if *SSD* refers to his main CB or the RCD (easily identified by the test button).
My RCD trips for no apparent reason and an electrician or two now claim it is the supply.
This licensed Aircraft electrician fails to see how that can be. Anybody ?

Shaggy Sheep Driver
20th Feb 2015, 16:31
Airship, do pay attention. Mrs SSD's intervention was at 07:30 just after she'd got up to a cold house, the central heating not having come on at 07:00 as programmed.

I'll keep it simple. Here's a timeline:

04:30, power fails.

07:30 SSD woken by Mrs SSD.

07:35 Power restored.

07:40 SSD's beauty sleep resumed.

PS - a stopped clock told me the power had failed when it did.

20th Feb 2015, 16:34

Thank you for supplying a timeline for the events of the early morning hours. Perhaps some of the resident Einsteins will now be enlightened. Maybe not.

Shaggy Sheep Driver
20th Feb 2015, 16:39
Just remembered another clue that may or may not be relevant. Adjacent to the distribution panel is the leccy company's LCD-display consumer meter. It has a red light that normally flashes once every few seconds. This light was on solid. It resumed normal flashing once I reset the Master CB.

Anyone know what that solid red light means?

20th Feb 2015, 16:42

The solid red, non-blinking, light is further evidence of a transient surge on the main line. :ok:

20th Feb 2015, 16:42
The OFSO household has similar problems, except it is the ELB that trips.

Frequent explicable causes: power surges, lightening.

Rarer causes:

Rainwater getting into a cable duct and to a junction box hidden deep inside the inaccessible bowels of the house. After first trip all is OK until violent winds outside move the liquid inside the junction box, more trips until water dries up. I found the leak on the outside of the house (it was through an external lamp) and sealed it. And replaced external lamps with solar lamps.

Insects in the cable duct shorting the mains. They only do this once.

Female Staff unable to understand that even with a three phase connection there are limits to how many appliances one can have on at once: pool pumps, heaters, washing machine, tumble dryer, oven. Following appropriate chastisement of female staff this doesn't happen too often.

20th Feb 2015, 16:43
SSD, are you trying to tell us that it was a mains-powered clock or other device which leads you to believe that the power went off at 4.30am then? I must admit to relying on my mobile phone as an alarm clock. And whenever the mains electricity goes off, most of the clocks on my domestic appliances such as TV, freezer etc. just flash 0s without somehow preserving for posterity the time at which the outage occured. ;)

20th Feb 2015, 16:56
I'm confused.....

0430 Power fails.
0730 SSD woken by Mrs. SSB

Q: At 0730 why were you awoken by Mrs. SSB? If you were both in bed, nice and warm, why would Mrs. SSB bring this to your attention?


Insp Jacques Clouseau

20th Feb 2015, 16:56
I had an electrician put some more power points in my workshop/garage last year and whilst here he recommended putting a large copper rod into the ground which then connected to the main board. He tried one rod a metre long but wasn't happy so attached another one and then measured what I'm guessing was the resistance, I'm on very sandy soil. Since then my main CB hasn't tripped so I'm guessing this is a better earth he has put in. He told me at the time but I've forgotten since. :O

Shaggy Sheep Driver
20th Feb 2015, 16:58
That's it, Airship. It's a bit of history I quite like - a mechanical digital clock from the days before electronic displays were common. It's driven by a synchronous motor and has 'flip-over' digits, so stops at the time the power fails. Reminds me of that lovely departures board at Euston that made that rapid running clacking sound running sequentially along its whole length as it periodically updated, the destinations, times, and platform numbers tumbling past.

Everything else in the house in the form of an electric display not only goes blank when the power fails, but re-sets itself to the correct time on restoration of power. Crikey, I remember when you needed racks of TTL logic and a 'Ruby signal receiver' to do that; receive time from Rugby, hold it in a register, compare the register to what the clock is displaying, fast step the clock until clock=register. I almost built one many years ago. It would have cost hundreds!

I did build a TTL digital clock back before anyone else had one. It used mains frequency chopped by a zenner diode to approximate a square wave, fed into a series of TTL decade counter chips and 4 BCD to decimal TTL converter chips to drive the 4 Nixie (gas discharge) display tubes I got out of an early electronic calculator. With its power supply (including a minus 180vdc supply for the Nixies) it ran hot but it worked!

PS - dazdaz's post - I see a timeline didn't do it.

And up until she got up, I was sleeping with my own wife, not Mrs SSB, whoever she is!

20th Feb 2015, 17:07
Note to self: Next time, marry a woman who can reset the main CB herself. :zzz:

20th Feb 2015, 17:08
In BC we not only have ELCBs to cut off circuits where the outlet is near the sink or in a bathroom but we also have to have Arc Fault Circuit Breakers for all bedrooms. These are expensive ($90 each as opposed to regular CBs which are about $5 each,) but also can be very sensitive and can trip when just plugging something in. As outlets don't have switches and often appliances don't either, (It is permissable here for an appliance to be energized by just plugging it in,) these things are a real nuisance.

Often they won't reset if anything in the room is on, including clocks, lights etc. As we have three circuits in each bedroom which include double and triple switched lights you can't tell whether they are on or off from the switch positions. Entails much running up and down stairs to fix.

That's another difference here. It is normal to wire lights into same crcuits as power outlets. Daft system.

20th Feb 2015, 17:11
Generally I don't rate useless (in the 'handy' sense) females, however I made an exception fro Mrs VJ. As she says, "You didn't go out with me because I was handy."

Shaggy Sheep Driver
20th Feb 2015, 17:14
Note to self: Next time, marry a woman who can reset the main CB herself.

Oh, Mrs SSD had identified the tripped breaker and could easily have reset it herself. However, she is bright enough to realise that the real issue wasn't the tripped breaker, but what had tripped it. So she left all 'evidence' in place as she found it, and referred it to me as the house leccy person. She'd even put fresh batteries in the torch by the time I came down!

Good call!

Interesting that rgbrock1 says the solid red light on the consumer unit points to an incoming mains problem. Can anyone else add to that?

20th Feb 2015, 17:19
Many thanks SSD, that explains it! I do remember those clocks. They made quite a nice soothing flop everytime the digit flipped over as I recall it.

PS. dazdaz1 obviously not following closely - perhaps due to early TGIF?

Shaggy Sheep Driver
20th Feb 2015, 17:38
A bit of Googling indicates that the red light on the leccy meter being on all the time might be an indication of no load on the meter, which you'd expect under the circumstances.

20th Feb 2015, 17:50

Yes, and no load on the circuit means...... no load at the meter. A transient spike/surge on the mains: I'll bet on it!

20th Feb 2015, 18:05
SSD - indication here is that the flashes are in sync with the usage rate.

Flashing LED on Electricity Meter - Education (http://www.reuk.co.uk/Flashing-LED-on-Electricity-Meter.htm)

Thus a constant light (infinite time between flashes) could merely show that no energy was being used, which fits your case.

Shaggy Sheep Driver
20th Feb 2015, 18:15
Here's that digital clock I built!

Practical Wireless Magazine April 1972 Build A Digital Clock Transistor Tester | eBay (http://www.ebay.com.au/itm/Practical-Wireless-Magazine-April-1972-Build-a-Digital-Clock-Transistor-Tester-/121474593869?pt=UK_Collectables_RadioTelevision_Telephony_SM&hash=item1c4873344d&nma=true&si=Hvs9OQxkjvTzyor5s79zKUwVKPc%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557)

20th Feb 2015, 18:23

Absolutely no energy being used? No fridge, no heating, no clocks, no nothing? I find that difficult to believe, no?

20th Feb 2015, 18:26
If I read SSD correctly, there was a constant red only when the Master CB was tripped.

20th Feb 2015, 18:30
Roger that, Fox3. Read it incorrectly. Mea culpa.

west lakes
20th Feb 2015, 18:56
It is very, very rare for an "event" on the UK supply system to trip anything in a house. Some of the effects commented on by our US cousins do not exist or occur in the UK (surges, brown outs)

By Main Breaker I assume you are referring to an RCD, easily spotted it has a trip/test button on it (you do test it regularly don't you)
If you look at it it will probably have either 30 or 100mA on the case this is the difference in current between the live & neutral required to cause it to trip and they are designed to prevent injury from electrical shock if anyone in the house makes contact with a live conductor or any other live to earth or neutral to earth fault occurs
The higher rating possibly 63 or 80A,is what it can carry but they are not designed to trip for other than an earth fault at the above value
The other MCBs on the board will be between possibly 6 and 45A and protect from live to neutral or earth faults of above that rating.

If it is an RCD they can trip for a number of reasons: -
Lightning in the area as stated
A developing fault between live or neutral to earth on a kettle or cooker
Damp in an outside light, socket or connector
Too many computer type power supplies connected as they all have a leakage current to earth
A developing wiring fault or damp in a household socket or fitting, maybe in a bathroom or kitchen
Some fridges with an auto defrost feature
Devices with motors that are failing
An insect in an outside or inside fitting.
In older properties or those with outdoor shed power could be a rodent starting to eat cables

And many more

If it's a one off I would ignore it, if it continues or gets worse you may have to fault find by leaving, as far as possible, appliances unplugged (not just switched off) to see if that cures the problem.
Failing all that you may need an electrician

Anyone know what that solid red light means? That there is a supply to the meter but nothing connected to it, the flashing increases as load increases BTW

The solid red, non-blinking, light is further evidence of a transient surge on the main line.Might be in the US, absolutely NOT in the UK

I had an electrician put some more power points in my workshop/garage last year and whilst here he recommended putting a large copper rod into the ground which then connected to the main board. He tried one rod a metre long but wasn't happy so attached another one and then measured what I'm guessing was the resistance, I'm on very sandy soil. Since then my main CB hasn't tripped so I'm guessing this is a better earth he has put in. He told me at the time but I've forgotten sinceMore than likely he spotted that at some point a particular type of UK (and CI) earthing system had been used in the garage (exported from the house) which should not be.
So will have fitted a separate earthing system for the garage to improve overall safety

20th Feb 2015, 19:03
Our power supply comes in on wires overhead. As a result our ELB can detect a thunderstorm several miles away and inform us by cutting off power. UPS back-ups keep computer and other equippy alive.

Shaggy Sheep Driver
20th Feb 2015, 19:15
Thanks west lakes. All of that makes a great deal of sense.

mr fish
20th Feb 2015, 20:08
laying in bed a few weeks back, about 2am, reading away the early hours and I noticed my reading light dimmed VERY low a couple of times.

my bulb is (was!!) a halogen type with a glass bulb cover.
upon the third dim..it brightened above the usual rated level and BANG...the shroud exploded and showered the bed and floor with shards..i very nearly s**t myself!!

clearing the mess from my surroundings I failed to notice 5p sized piece was burning a hole in my skin resulting in a cute mustardgas style blister the following morning.

took days to heal and I now have a nice scar to remind me to switch off the next time we have a surge...


west lakes
20th Feb 2015, 20:50
to switch off the next time we have a surge.

I'm guessing you may live in or near a rural area.
The dimming was caused by a fault on the high voltage network where the voltage was depressed until the circuit tripped.

Imagine it as a hole in a water pipe, all the water rushes to that hole so reduces the pressure (voltage) everywhere

The brightening was caused by the resistance of the bulb filament reducing as it was failing. To be hones most bukbs should contain a small fuse to prevent them exploding, far, far too many don't. This is also why a bulb blowing can blow fuses or circuit breakers in consumer units.

There is only one, and I do mean one situation where some households in the UK see excessive voltages and this was not it.

20th Feb 2015, 21:23
Suggest you have a look in your garage.
When our RCD tripped out at 2.30 am (discovered on waking, and calculated from stopped clocks), the cause was eventually traced to a fallen light in the garage which had shorted and tripped the RCD. And it hadn;t fallen, it had been broken by the thieves who needed some privacy to steal my TVR. They failed.

cockney steve
20th Feb 2015, 23:40
Bear in mind that the IEE (leccy installer's governing body) keep changing the rules every few years to keep the tills ringing.....OOPS, I meant "to enhance consumer safety"....so, no longer is it a RCCD...it's now called a RCBO

Also, the whole thing has proven what I suspected with the introduction of these devices....THEY ARE A DAMNED NUISANCE!
When we originally just had one, Irons, Immersions, kettles and washing-machines were particularly prone , due to mineral-powder insulated elements, to absorbing damp.... I new a guy, built a state-of art house and his wife bought 3 new irons in the first 9 months.....i suggested to keep the iron in the airing-cupboard (warm and dry).... Switch on appliance....heat drives moisture towards cooler ends where it condenses or reaches sufficient concentration to pass 30 Ma to earth.....trip knocks out......wifey trundles off to garage accesses main distribution board and resets....sometimes this takes a while , as the moisture has to "thin out" in the faulty appliance in order to reduce it's leakage current....gets back to the job in hand and the trip blows again....rins/repeat until the element insulation has fully dried out.....As a Kludge (personal opinion) we now have to have our supply-boards split , with 2 separate RCCD/RCBO -protected sets of trips....AND EACH FLOOR HAS TO HAVE IT'S CIRCUITS DIVIDED BETWEEN THE TWO.
To me, that is an implied tacit admission that the system was flawed, as a minor fault could leave the whole property without power.....now, theoretically, , a fault will only disable PART of the power-supply to each floor.

In the case of Alarms, fire detectors and freezers, one is allowed to have a third, unprotected by earth-leakage section on the board...so, only a major fault will trip a circuit -breaker fed from that section....this is termed a "High Integrity " board......don't start me on the cable colour-code change..... blue used to be "Live"....now neutral....Black used to be neutral....now live :eek:

as is brown (a natural "earthy" colour! ) world's gone mad.

me- not qualified either, but having seen a number of "professionals" make fundamental bodges.......

20th Feb 2015, 23:56
I recall helping one of my students with the stage lighting at school one Sunday. He was the 'expert', having done the National Theatre Stage Technician course. He received a electric shock whilst operating the mains panel. No serious harm done; he asked me what he'd done wrong. I examined his actions, and the panel from a distance, and could find nothing wrong.
"Shall I try it again?"
"Can you try it?"
"No. We'll call the electrician"
Loss of my credibility as an engineer with student (he said much later).

Three hours later, professional electrician turns up, laughs at us, repeats student's actions. Gets mains shock also.

My credibility with student regained, plus a bit.

An ex- is a has-been, and a spurt is a drip under pressure.

Ground loop is my best guess. Lighting rigs are capricious beasts.

21st Feb 2015, 00:06
When I built my own house I installed a two row distribution box. The upper row looked after power in the upper floor, in this case the lounge, kitchen etc, and the other looked after the power on the lower floor, bedrooms etc. The lights were wired the other way round. Each row had its own RCCB so if that tripped it meant that either the lights OR the power went out on one floor.

I lived in it for ten years and there were about three outrages that caused an RCCB to trip. Not that much of a problem because either a table light or a ceiling light was going to work.

21st Feb 2015, 00:34
A slight comment, nothing to do with the thread.

One of my jobs I had, in fact the second, was as an assistant in a wholesale electrical supplier in Bulawayo in 1958. At that time ALL new buildings in the city were required to have CBs on every circuit. They were not ring main as per the UK system, they used metal conduit and 14.1087 wiring. Coming back to the UK I found that the old wire fuse systems were still being used.

I lived in China for many years and I learned the Chinese system so I could restore power in short order. This is not helped by the fact that Chinese electricians qualifications are time served, i.e. got the hang of it.

On one particular day the power in my apartment went thud. They had a row of circuit breakers in the box so I went through them progressively trying to find out which circuit was throwing the main RCCB. This was unsuccessful so I called the landlord and he sent out an electrician. He did the same as I did and then he picked up his tools and walked out. I asked the landlord what was the problem. "Too difficult" was his reply.

It was now up to me so I then went around the sockets pulling them out to assess whether there was a wiring fault. The standard of wiring was appalling! The colour coding seemed to depend on which reel was handy at the time and the box was full of joints sealed with insulation tape. Even with the power off two of the sockets were live because they were wired into the apartment next door. Eventually I traced the fault to a bathroom shaver socket. The wall had not been chased out enough and the wires had been pressed again the blocks. The socket was still not solid so pushing a shaver plug in an out had caused the wires to chafe and ground to earth. Two minutes with a screwdriver and a flat iron and the problem was solved.

Loose rivets
21st Feb 2015, 01:09
What may I ask did you use the flat iron for?

How did you know it was at 0430 if you were asleep?
How do you think? Go on, guess... it's not 'ard! [/QUOTE]

We DON'T wish to know that!

clearing the mess from my surroundings I failed to notice 5p sized piece was burning a hole in my skin resulting in a cute mustardgas style blister the following morning.

You failed to notice a mustardgas thingy burning a hole in your skin!! :uhoh: Even if it was cute, I'd say you need to get your neurological sensors inspected. :p

Loose rivets
21st Feb 2015, 01:30
UK. New regs it seems require - or will shortly require - ALL circuits to be protected by earth leakage detection. A while back things like the kettle and the oven leaked so much that it would trip the 35ma detection almost on a daily basis. Now, they must not.

It used to be thought that lights should not cut out when you were groping your way to the fuse box. Now, some lights on one RCD and some on the other.

I can't say much about having a torch at hand, I put one of the first Crabtree Starbreaker units in my home and refused to leave the lights unprotected. Within two weeks of the new unit being in, the house was plunged into blackness by a leaky soldering iron. Never felt a tickle, but when I felt it to see if it was warming, (whey did we do that?) all went black. As it happens, it would not reset, and I had to fabricate a link to tide me over until the Crabtree rep turned up. It was their flagship, so he was greatly concerned.

Now a 5 + 5 is typical with both sets of 5 having an RCD. Yes, both have a TEST button. And yes, there are NO unprotected CBs.

Often, 6a CBs will trip when a filament bulb 'pops'. New bulbs are a different story. This is a good thing, though 6a at 240v will kill you stone dead if you don't get kicked away. Indeed, that's why I wanted that circuit protected and bo-lox to the regs.

Why is the OP's unit cutting out?

But - each circuit in the house has its own CB. None of these had tripped. Only the 'master' CB which powers all the others. How could this happen? Surely whatever caused the event should have tripped the CB on that circuit. I can see it might also trip the 'master' CB, but I can't see how the 'master' can trip yet the individual circuit CBs remain untripped.

Smells of an RCB and not a main CB. The latter are often 60, if not 100 amps. You'd know if something popped that. It has to be a RCB of one flavor or another . . . doesn't it?

As said above, the RCB / RCCB or what-have-you will have a test button on it. Right next to the RESET button. Some Distribution boxes don't even have a main switch/breaker, though most do, a big red one at one end.

21st Feb 2015, 01:41
airship? WTF? 04:30 IS this morning.

Not to a civvy bedwetter :p:p:p

21st Feb 2015, 01:49
Is it possible that you have a surge protector after the main CB and before the branch CBs? That would pop the main CB on an incoming surge.

After an excellent landing etc...

21st Feb 2015, 05:55
I had one of these things pop when someone slammed the front door.:confused::confused:

21st Feb 2015, 06:39
Weird stuff happens.

I recall being in an office block that was under construction. One floor was fitted out and was being used as the site office. As far as I could see the electrical installation was final. I looked after a small server which had a associated battery backed uninterruptable power supply (UPS). The battery in it was about the size of a car battery. I needed to add a new network switch and had in my hands a fairly meaty Cisco Catalyst 3750. Ideally I wanted to use the UPS for it. As I was standing there cables in hand it occurred to me that perhaps the load might be too much for the UPS.

A few seconds consideration later I plugged it in. It's only a little switch after all.


Entire floor of 100 people each with a computer now blacked out.

Read label on switch, oops! A bigger number that I expected. Too much for the UPS but no fuse or breaker tripped on UPS or even its 13A plug.

Building full of people who knew about t'electric. No breakers tripped on floor, much head scratching. Tripped master breaker found in basement and power restored.

I, finding it inconceivable that my little switch/UPS had tripped such a big circuit plugged thing in again - just to confirm that it wasn't me. Same result. Many very worried looking people scurrying about, me creeping out quietly to return when stuff had cooled off.

Seems impossible I know, but it happened.

My assumption is that there was some resonance/oscillation created in the circuit that tripped the more distant and higher capacity breaker. It may have been an RCD.

21st Feb 2015, 07:43
Some UPS's have a lot of earth leakage.I've had a 2.8kVa UPS trip out the first 30mA RCD up the line before.And again when reset.And again.....

21st Feb 2015, 08:43
Lightning occasionally trips the breaker for our electric gates but because it is in a separate panel in the pool house we don't notice it until we arrive and they won't open. It always seems to happen in the dark, and raining, when we are on the outside. We learned quickly to keep the special key to open them manually in the car, but fumbling to find the slot for it, through the bars, on the opposite side, is a challenge. :*

Echo Romeo
21st Feb 2015, 16:42
Get a sparks to come round and perform an insulation resistance test. If you have a leakage to earth, and he knows what he's doing he'll find it in next to no time.

victor tango
21st Feb 2015, 17:40
Need an electrician to go round Millibands house.
All the lights are on but nobodys at home ?:rolleyes:

Loose rivets
21st Feb 2015, 23:13
I lived in it for ten years and there were about three outrages that caused an RCCB to trip

F E Driver . . . what on Earth did you do? ;)

22nd Feb 2015, 08:17
Yes, we had to change our filters when RCDs were introduced - but that was over 30 years ago IIRC.

cockney steve
22nd Feb 2015, 11:21
F E Driver . . . what on Earth did you do? 
Obvious, innit? he sparked-off a load of outages.