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[renluop]

Our wiring is protected by a Memera2000 consumer unit. Twice in last week, once when we were out and last night while we slept, we found that all apparatus covered by the power circuit (not lighting) was not working.

None of the switches had tripped, however, and, given the situation of the occurrences, overloading seems unlikely (at least to me ).

Is someone here less electricity challenged than me, who might be able to suggest why  we are having this problem?

BTW I am also wondering if some of the computer problems of late might somehow be related to power supply.

[roseway]

If the power circuit is out but the MCB (miniature circuit breaker) hasn't tripped, then it sounds as though the MCB has failed and needs replacing. It's an easy DIY job if you know what you're doing, but it's probably best to call in a sparks to do it.

BTW I am also wondering if some of the computer problems of late might somehow be related to power supply.

Quite possibly. If the MCB has been intermittent (sparking perhaps) that would certainly disrupt any computer.

[renluop]

I'm guessing the MCBs are the little brown switches? But how does one find which is the culprit, when none has tripped?

Yes, it will likely be a sparks job, but I like to try to understand, however useless that might be.

[roseway]

The MCBs are labelled, although I can't read the labels in your picture. The labels should make it clear which MCB controls which part of the circuit. You may have separate power circuits for upstairs and down, and maybe a separate one for the kitchen.

By the way, although a failed (or failing) MCB seems the most likely explanation, it could also be a loose wire somewhere. Do get the sparks in.

[renluop]

I should have said the pic was not of my set up, just lifted from a pdf.

Will now find what local bloke is recommended.

[broadstairs]

I agree with Eric, get a sparks in. If that is very similar to your consumer unit it looks like a split load one which complicates things. If you have more than 1 power MCB and all of the power circuits went off then I'd suspect the consumer unit itself and you dont want to mess inside that as all hell could break loose if you get it wrong, touching the wrong thing in there is LETHAL!

Stuart

[renluop]

Got someone coming at 2, the chap who deals with our church electrics.

[sheddyian]

Glad it's being looked at, best not to mess with these things if you're even slightly unsure.

Out of interest - you say that twice last week the power circuit was out, but nothing had tripped.  How did you get it to come back again?  Or did it do so in it's own time?

Ian

[renluop]

He thought it may have tripped but I hadn't noticed the slight movement of the red switch. Advised to pull to "off" and use reset button if in similar situation. Also said that the equipment is very sensitive to current changes and other things like even slight dampness, so faults like mine are more frequent in winter. Other possibilities were older fridges', freezers' deterioration in the switching area. ( As ours are just over 10 yo and the washer dryer somewhat older that might not be unlikely). Suggested that if the situation does not recur for some time not to worry, but if it does in the near future to call him and have tests done.

[sheddyian]

Yes, damp would cause "leakage" to earth, which would trip a breaker.  And agree with the thing about older fridges/freezers, used to be quite a problem I understand.

Also a problem, possibly not affecting you, is too many computers on the same circuit.  Not because they overload it (as such), but the PSUs all leak a little bit of current to earth as part of the filtering in them.  Too many of them makes the leakage current exceed what the breaker regards as fault condition current, and so it trips!

Electrician friend who was wiring up local college used to bemoan this.

Ian

[c6em]

Standard domestic RCD unit in consumer units is set to allow up to 30milliamp leakage current to occur before tripping.  (you can get them at different ratings for special applications if you go to a industrial supplier  - and you know what you are doing!)
Obviously this is 30ma the the sum of all leakages in all circuits fed through them.

The individual trips are merely current overload trips - these are known to nusiance trip out when an incadescent bulb in the cct blows as the sudden surge of current as it goes exceeds the trips time/current relationship curve and off it goes.
Again you can get breakers with a slight delay in them when reacting to short term overcurrents to solve the problem, but no one uses them (domestically anyway) mainly 'cos some blithering idiot who can't read the rating designation on them will eventually fit one in a power circuit where a delay is NOT required.

Garage circuits are another notorious cause of nusiance tripping (damp etc) if they are wired into the main consumer unit and not from a separate board....too expensive to do it properly innnit.

The exact cause of seemingly random occassional nusiance trips of the RCD are very difficult to find - I don't envy you.

[renluop]

Thanks for the info (and encouragement ), but it's not looking good as another incident at 10:10 last night. Wifey noticed when she returned later from grandkid sitting that the fridge door had not sealed shut, something it's been prone to of late.

[sevenlayermuddle]

In my own experience of tripping RCDs, while there may be other causes, first and foremost be suspicious of any appliance that involves water.  Specifically, in the 20 odd years these things have been around, I have tracked seemingly random faults as follows...

1). The 2-way valve in the central heating system.  Clue was the trips sometimes followed after the room thermostat triggered.   Easy to demonstrate once sussed, but seemed totally random until I fugured it out.

2). A cordless plastic electric kettle than had sprung a leak, allowing water to drip onto the base unit.  Tripped ten minutes or so after boiling the kettle.

3). A dishwasher which was leaking water from an intrnal hose, dripping onto a circuit board.  Clue was that it tripped about half hour into the dishwasher cycle, but took me an embarassingly long time to figure.

I hope maybe that provides some inspiration?

[Ezzer]

Some trip switches have 3 positions, on , off , and in the middle tripped. So it may not look to obvious that a trip has occured. But the switch should need manual resetting back to the on position. This is so you can tell it was a tripped switch as opposed being turned off manualy.

Some appliances give a spike in consumption. AC Motors, Ballasts, etc These should have the relavent protection to cover the momentary surge built into the device. This shouldn't pass through to earth unless there's something amiss. Sevenlayermuddle listed some good exsamples.

If the Fridge is the culprit then it does have an AC compressor motor. Each time this starts it draws for a split second much higher amps than normal. But as other have said, may be better for a qualified 'leccy to have a look so you can be sure all is well and hopefully isolate the culprit.

[renluop]

Until the freezer can be emptied etc, we have inserted a plug in RCD in the hope it prevents the main one trippimg.