Electrical supply tripping out

kev7378 said:
Have we all made it this far?
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Obviously, otherwise we wouldn't all be on the forum!

Do you have any statistics for how many deaths there were before RCDs became commonplace which would have been prevented by an RCD? I've not died yet, and my house (nor any previous houses) is not fitted with one (I admit to using one for my garden power tools, but I do not accept that it would be needed even if the power cord was sliced through by my double-insulated mower).

I suspect this is a case of "we have the technology to do this, so we'll make it compulsory". No, I do not believe in protecting people from being blithering idiots. Tonsils and adenoids are supposed to have a protective function, but they get whipped out if they are causing any trouble, on the basis that we can manage without them. Ditto an RCD - we can manage without it, and if it is a cause of inconvenience it is more trouble than it is worth.

However, as you must surely realise by now I specialise in playing devil's advocate, and raise points which otherwise go accepted without question. RCDs may very well be a Very Good Thing from the point of view of electrical safety, but they come with a cost - both in the additional expense of their fitting and as an additional point of potential failure. Thus their mandated installation is not without its down side.

The Welsh government intend to make sprinkler systems compulsory in all new-build houses - but damned if I want one. It is more likely that a fault in the sprinkler system would result in possessions lost by water damage than lost through fire (and then the sprinkler system would ruin everything else by water damage anyway). I've never had a fire, but I have had plumbing leaks (and the more plumbing there is, the more likely it is there will be a leak).

As far as Martin's problem is concerned, the easiest way forward is simply to replace the RCD and see what happens.
 
Black Hole said:
As far as Martin's problem is concerned, the easiest way forward is simply to replace the RCD and see what happens.
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Agreed. If it is the RCD that has tripped. He said he lost all electrics, but is it normal to put lighting circuits on the RCD? I thought not. If that is the case, it seems that it is the main breaker that is tripping.
 
MartinLiddle said:
Incidentally there were power cuts in the surrounding homes at about the time the breaker will have tripped (due to road works and contractors damaging supply cables) but none of the neighbours had tripped breakers. Could a power cut (or more likely a surge as the power came on) cause a breaker to trip?
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My opinion is yes (based on experience and talking to others): power cuts can cause things to trip (usually the RCDs, maybe the MCBs (but not the "Main Switch")).

As it happens we had a lot of power cuts here a few weeks back. When the power went off cleanly and came back on cleanly, the RCDs were fine. However, there were also cases where the power died down before going off, or flicked on/off rapidly (and so on), or did not come back on cleanly: then some RCDs tended to trip. Neighbours were, I was told, affected in the same way. The MCBs may have tripped also (I cannot recall). Eventually I switched off the "Main Switch" for the rest of the morning to save on the wear and tear.​

There was also some "electrical work" locally a while back that caused RCDs to trip (that is, not just in my house); which suggests to me that things occurring outside of the house can also cause them to trip.​

Talking of the effect on neighbours: a few winters back there were power fluctuations for a few days, then it went off and stayed off for several days (it took them a while to acknowledge/locate/fix the fault). The thing was, out in the street it was only every second (or was it every third? I cannot recall) house that had no power. The reason was, it seems, that each of the cables supplying the power ran to alternate houses and the fault was that one of these cables had "burned out" somewhere. So it is possible to have a power cut; but for neighbouring houses/houses across the road to have power/cleaner power.​

MartinLiddle said:
1. How do we diagnose what is causing the trips? When the property is unoccupied we turn off as much as possible so the possible culprits would be the central heating system, the fridge/freezer, the burglar alarm, the HDR-2000T PVR and the telephone answering machine (plus anything I have forgotten). We have consulted an electrician who said trial and error was the only way; any more scientific test we could try?
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We have our freezer on a completely separate circuit and consumer unit; and so far it has never tripped (except when the bulb inside blew); even with the "messy power" of a few weeks ago.

In case it ends up being deemed to be "power cut induced" trips: I think you need to unplug stuff as well (not just switch off) if you don't already. Extension leads and surge/filter strips and so on can all add to the "problem" (or be an item at fault). I did once have a surge/filter strip with an occasional problem (pre-conversion of house from fuse box to "consumer unit with RCDs/MCBs": but I used plugin RCDs at that time which made testing "easy")...

It is only a few years since I had the house wiring "tested"; I think it was like £175, so you could consider that in case there actually is a wiring fault?

The more scientific way: It would also be possible to have individual pieces of equipment and so on tested; its probably not really DIY as I think sufficiently accurate equipment is still very expensive.

Other than that, "guided" trial and error appears to be the only way left when looking for a fault (including swapping out the RCD/MCB devices). As MikeSh said, you'll need to know which device(s) actually tripped and identify what is on each one to be able to plan a strategy (or it may even offer a clue). Some easy, some not. But it sounds like, this is only a problem if there has been a power cut? (although I guess you could use the "Main Switch" to test; although that is a clean break test only)?

Are "the fridge/freezer, the burglar alarm, the HDR-2000T PVR and the telephone answering" all on the same ring (cumulative leakage)? If possible split them up. If they are not all on the same circuit, can you move any of them them? Divide and conquer. No "broadband"?

Your "consumer unit" should be labelled (as to what is on each RCD/MCB combo); although mine was found to be incorrect, so I had to test it all and relabel.

MartinLiddle said:
but none of the neighbours had tripped breakers.
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I think it is likely to also be equipment dependant.

And, possibly, examples of other things might help to cause a problem/increase the "imbalance/leakage":

Birds/bats nesting on the down lighters in the loft.
Rodent has chewed on some cables.
Cat/Dog/other pet has chewed on an extension lead/power cord.
Earth loops?
​
Hope this all make sense and is correct (it was a simple reply to start with!).
 
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kev7378 said:
Talking of the effect on neighbours: a few winters back there were power fluctuations for a few days, then it went off and stayed off for several days (it took them a while to acknowledge/locate/fix the fault). The thing was, out in the street it was only every second (or was it every third? I cannot recall) house that had no power. The reason was, it seems, that each of the cables supplying the power ran to alternate houses and the fault was that one of these cables had "burned out" somewhere. So it is possible to have a power cut; but for neighbouring houses/houses across the road to have power/cleaner power.
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The main feed in the road is a 415V, 3 phase feed from the local distribution transformer. Domestic properties usually have a single phase feed taken from one phase and the neutral, which gives the 230V supply. To keep the load on the phases reasonably balanced it is normal to connect each property along a road to the 'next' phase from the previous one. Hence if there is a fault in one phase (eg. a fuse in a distribution cabinet pops) then you will see one in three houses, and possibly street lights, are out. (This is useful information to pass up if you are reporting a fault as it tells the power company they are probably looking at a fairly local issue but not at your house.)
 
Black Hole said:
(I admit to using one for my garden power tools, but I do not accept that it would be needed even if the power cord was sliced through by my double-insulated mower).
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You are missing the point. As you cut through the power cord, it is likely that the blades of the mower and any other conductive parts can become live and lethal. The double insulation feature is completely irrelevant in this case.

http://www.electricalsafetyfirst.or...ds-thousands-of-gardeners-in-hospital-a-year/
 
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Mine would be completely safe, even in those circumstances, unless you were to grab the end of the exposed cable. This is correct product design.
 
Cutting the cable will trip the MCB not the RDC if there is high live/neutral current with, hopefully, no path to earth through the user thanks to the secondary element of the double insulation (i.e. plastic outer casing).
Ah, thinking hedge trimmers here, not mowers.
 
Fuse/MCB is not effective when there is no earth conductor to take the fault current - you are relying on the severing blade being conductive and shorting the live to neutral. Were the blade earthed, the fault current would be diverted safely and cause the fuse to blow.

An RCD doesn't prevent exposed live parts (if there is no path to earth), or being shocked by contact with them (for the time it takes the RCD to trip). It would however prevent a rescuer also being shocked.

Far better that products are properly designed to be safe under foreseeable failure circumstances, including the entirely predictable situation of a mower/trimmer slicing the power cord, or a drill going through the cable in a wall, than for the manufacturer to rely on 'safety' being provided externally. This was absolute mantra when I was working in standards compliance, and it's built into product standards requirements such as CE. If people are getting electrocuted by simply having an accident with the power cord, the mower in question should never have been on the market.

The fuses/trips in the house distribution board are not there to protect things plugged into the sockets, they are there to protect the house wiring from overload. The fuse in the plug is there to protect the lead, and any protection the actual equipment requires should be built into the equipment (not rely on the plug fuse).
 
MikeSh said:
The main feed in the road is a 415V, 3 phase feed from the local distribution transformer. Domestic properties usually have a single phase feed taken from one phase and the neutral, which gives the 230V supply. To keep the load on the phases reasonably balanced it is normal to connect each property along a road to the 'next' phase from the previous one. Hence if there is a fault in one phase (eg. a fuse in a distribution cabinet pops) then you will see one in three houses, and possibly street lights, are out.
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Yes I have seen exactly this effect. I have only stayed in Buxton (nice place) twice in my life. On the first occasion we had rented a house for a family party and when we arrived the power was off. As dusk arrived it was obvious that power was off to every third house along the street. The owner was very apologetic and provided a couple of bottles of wine and a supply of candles. the power came back on the next day. The second time was earlier this year when we were staying in a large hotel in Buxton. At first the power in the room was fine and we boiled the kettle without problem. Later in the day I tried to put the lights on and realised that all the power to the room had failed. Luckily the there was a consumer unit in the room and so I could experiment to find the culprit. It turned out to be the kettle base. It was an unusual design that had the based mounted in to a tray and the tray was mounted on rollers so that you could pull it forward out of the unit to make it easier to remove the kettle. I had pulled the tray forward after it boiled and I think that was when the supply tripped. It looked to me as though the base had been repaired at some point and I suspect the repair was bodged.
 
Thank you to everybody who has replied. I will be visiting the house later this week so I can check exactly what happens when the relevant breaker is tripped. Assuming it is the RCD I will investigate replacing it. I will also implement Wallace's monitoring strategy.
 
Just as an aside, I have hard wired an rcd onto a brand new toaster that cost over £100. Why they can't fit one inside for that much I can't imagine. I had to fit one to a neighbour's toaster too. We only have one rcd in our consumer unit but at least the neighbour only lost some power when a teacake tripped an rcd, whereas ours knocked the whole house out.
 
Trev said:
Agreed. If it is the RCD that has tripped. He said he lost all electrics, but is it normal to put lighting circuits on the RCD? I thought not. If that is the case, it seems that it is the main breaker that is tripping.
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If you only have one rcd, it is. Plus, a faulty bulb could electrocute you, so best include bulbs too.
 
So when the mains trips at night, you have to stumble around in the dark? No thanks. You are beginning to sound like a H&S man gone mad. (They all are).
If the bulb is faulty, then switch it off before you try to change it. If you are that frightened of lecky, always switch off at the main breaker before you touch anything. (That's the 'royal you')
"Caution, floor slippery when wet." I bloody well know that. I want to know when it is wet. Another stupid H&S 'thing'.
 
BH has a point about design, but how do you force fridge manufacturers to design fridges and freezers that do not catch fire? You can legislate, of course, but then you are in exactly the same situation of having to legislate safety as with rcds.

In all the talk of Grenville, I can't remember any talk of making appliances safer, just talk of stopping a tower from burning down because a fridge freezer was poorly designed.
 
Oh dear. One of the most dangerous mixtures - hazardous substance plus arrogance.
What happens if the mower cable is damaged and you don't realise? Add a bit of damp ... you grab it to move it ... Bye bye BH/Trev.
What about bulbs fed by two switches such as over stairs? Is it actually off?
The rules are there to try and protect everyone, even Darwin award contenders, but even sensible people make mistakes occasionally.
As someone who worked professionally with electricity I've used 'whole house' RCD systems for at least 40 years without any problems. Number of times RCD tripped in the middle of the night - 0; number of times the mains supply went off during darkness - many. Like me I'm sure most people can find their way to the loo and back to bed in the dark.

But we are now in the 21st century and things have moved on. My consumer unit now has 9 RCDs (RCBOs); one for each/every circuit.
And the lawnmower is battery :)
 
Mike0001 said:
Just as an aside, I have hard wired an rcd onto a brand new toaster that cost over £100. Why they can't fit one inside for that much I can't imagine. I had to fit one to a neighbour's toaster too. We only have one rcd in our consumer unit but at least the neighbour only lost some power when a teacake tripped an rcd, whereas ours knocked the whole house out.
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If a toaster tripped an RCD I would be taking it back immediately! How are these things getting through compliance testing???

The problem with an over-reliance on H&S is that nobody has to bother with "being sensible" any more, and they don't know how to be aware of danger when faced with it. Witness the kids (and older) quite blasé about walking across a road without a glance at the traffic, totally absorbed with their phone or whatever, happy to assume the traffic will spot them and stop.

What about the backlash that judge got recently, when quite reasonably she said that people out on the lash had a degree of responsibility not to put themselves in harm's way - and the plaintiff in the case agreed?

Cyclists appear to have a death wish - surely if they were aware of the accident statistics they would take more care to be seen at night?

With a burgeoning world population and no possibility of resources stretching, I'm surprised you lot don't think a little more hazard in our lives to weed out the poorer specimens wouldn't be a good idea. It's a reasonable bet it wouldn't be us!
 
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