An electrical/ELCB issue..

C_Mababejive

Hi all,

I have had a long standing an rare/intermittent issue with a main incomer that keeps flicking off.

The house is 80's built and the consumer unit is an MK grey metal type. It has a main isolator switch over on the right which i think is an ELCB with a small yellow push to test button.

The CU may have had rewireable fuses at one time but these have been replaced by MCBs.


I have an issue that might only happen a couple of times a year.

The Main incomer will just randomly flick off cutting all power to the house.

I have had a couple of people attempt to isolate the cause but no solution.

Inevitably it may happen when the house is empty cutting power to the fridge/freezer !

The other day i came home from a weekend away and it had tripped. This time the MCB for the downstairs ring main had also popped out.

I had it suggested that i should have a new CU fitted but then someone else said it might actually get worse as they are more sensitive.

Im now thinking a possible solution might be to fit a single MCB external unit fed from the elec meter output and with a socket outlet into which i can plug the fridge when going away

any thoughts?

Fightsback

Is there an RCD on the main incomer ?

If so you might have something there with an intermittent earth fault or short. Intermittent faults are a pig to diagnose.

Have you had a sparks look at it ?

There are so many possibilities here it's hard to say without first fully checking the condition of the existing wiring. Before the external MCB is fitted you really should root cause what's causing the trip.

bluesnake

Mine years ago also tripped a few times a year, but it was due to lightening storms. A few times though it was not lightening, but the element on the water boiler element and corroded internally, also to had a kettle do similar. The weird one was the water boiler as it was intermittent. The water boiler was hard to track down, but the kettle was easy. just flip all the circuit breakers off then, one by one switch them on again until it tripped and that isolated the kitchen. Then it was just a matter of unplugging everything and flipping the mains switch back on, then plug each item in again. The water boiler issue was tracked down by using a multimeter https://forums.moneysavingexpert.com/discussion/5298217

grumbler

Fightsback wrote: »

Is there an RCD on the main incomer ?

Is ELCB not essentially the same as more modern RCD? AFAIK, both do essentially the same job.

C_Mababejive

yes there is an ELB on the main incomer only. The original wired fuses have been replaced with mcb's with pop out buttons.

I had a couple of electricians to try and solve the issue but to no avail.

In the past when going away, i have unplugged lots of stuff,operated isolators,even popped out all the mcbs on unused circuits.

This time the mcb on the down stairs ring main also popped out along with the main incomer ELCB.

Im thinking the issue must be on the downstairs ring main but there seems to be no fixing it.

Fightsback

grumbler wrote: »

Is ELCB not essentially the same as more modern RCD? AFAIK, both do essentially the same job.

Moot point, MCB tripped on the downstairs ringmain with nobody in the house. The downstairs ringmain would be a good place to focus first.

Is it a suspended floor or solid concrete downstairs ?

C_Mababejive

Fightsback wrote: »

Moot point, MCB tripped on the downstairs ringmain with nobody in the house. The downstairs ringmain would be a good place to focus first.

Is it a suspended floor or solid concrete downstairs ?

Its concrete. All the downstairs power to sockets is dropped.

Fightsback

There is no magic simple answer to this one, it's a tick list.

Sockets, wiring, appliances, faulty MCB etc.

Do bear in mind as well a blown light bulb can trip a MCB, halogens being the worst offenders - didn't leave any lamps on connected to the ring main did you ? I know unlikely but just a thought to eliminate it.

System

Hi

If it is indeed an old ELCB, then it may be a VOLTAGE trip type. Which means voltage on the earth wire trips it out.

This can be from a neighbour, YES really, nuisance tripping your device.

Modern units are CURRENT operated, usually 30 milli-amps within 30 milli-seconds. 30 is for the protection of people, larger tolerances 80 and upwards are for property only.

Nuisance tripping on these is from 'filters' where a device has a filter that is connected across all the pins in a plug and very occasionally leaks a little bit to earth.

Changing the ELCB for an RCD will remove the neighbour nuisance tripping, but not anything with filtering.

Old ELCB's could hum, not because they don't know the words, but because of a partial leak running through the trip coil. I would listen for such a thing with all fuses in and then all fuses out, just in case.

Mains filters with values like this

Max. Working Voltage: 250V a.c. 50-400Hz 250V a.c. 50-400Hz
Earth Leakage Current: <0.35mA (250V, 50Hz) <0.35mA (250V, 50Hz)



would leak upto 35mA, on rare occasions it could trip your device.

Strider590

Get a plug in power usage meter, preferably one that has max/min memory, set it to read volts and watch your mains voltage periodically over the course of a few days.

Most foreign made appliances/etc are designed and built for 220-230v AC, but UK mains voltages can reach 250v AC at certain times of the day.

Almost all electronic goods will have VDR/Varistors to protect against transient voltage spikes, the job of these is to short excessive voltage spikes to ground and protect the equipment in the event of a mains fault or lightening strike.
Most of the above mentioned devices/etc are protected by 250v varistors, so you can now see a problem, in the UK these devices are often running at very near their limit or triggering point and after years of service can become a little too sensitive, they start to leak voltage, overheat and degrade further, at which point even a tiny mains spike could easily cause one to take out an MCB.

Check those mains voltages and make a complaint if they're too high, the UK standard is 240v +6% and -10% (about 255v AC maximum).

Mine can reach up to 253v AC and i've lost 2 PC power supplies in the last 3 years, both to blown varistors.

Fightsback

Strider,

It could even be careless nailing or screwing which has penetrated one of the cables.

In my current house when I first moved in (old 1920s house) there were mice in the loft thanks to header tank piping which was swiftly resolved with a pressurised new boiler and an excellent mousing cat. My point about a suspended floor is that you are much more likely to have mice and the beggers are prolific cable chewers.

PS that's one hell of spike to trip a 32amp ring-main circuit breaker