Consumer unit question trip

[spoony77]

Hi there
My main switch tripped on my consumer unit last night meaning the whole house was without electricity.
This was while we were asleep, what can cause this to happen?
Its never happened before on a power cut, and therefore is quite worrying as we dont want it going while we are on holiday etc.

Any advice appreciated

 

[ban-all-sheds]

Did you have any appliances running overnight?

 

[spoony77]

Only the fridge and all the usual things on standby (tv, sky, phones etc)

 

[PrenticeBoyofDerry]

Is the CU protected by an RCD? and it that that has tripped rather than the main isolator?

 

[kai]

Only the fridge and all the usual things on standby (tv, sky, phones etc)

I had the same problem, leaving TV's and Skyboxes on standby causes the main RCD to trip out, unplugging them or switching them off at the wall solves the problem - and saves you money off your electricity bill.

I run my fridge/freezer off a separate 2 way consumer unit on a NON RCD protected circuit, feeding two specially labelled socket outlets.

 

[JohnD]

I have known it happen when work was being done on the power lines near my house. The work started after midnight at weekends and the trips occurred during Saturday night/Sunday morning

I have RCBOs and usually only one tripped at a time.

 

[Steve]

I had the same problem, leaving TV's and Skyboxes on standby causes the main RCD to trip out, unplugging them or switching them off at the wall solves the problem - and saves you money off your electricity bill.

But if you have sky multiroom it is a condition of the contract that you leave all your skyboxes able to dial out on the same phone line 24/7, so they can check they are at the same property. If you turn them off at the wall, your effectively violating your contract.

 

[spoony77]

I had the same problem, leaving TV's and Skyboxes on standby causes the main RCD to trip out, unplugging them or switching them off at the wall solves the problem - and saves you money off your electricity bill.

But if you have sky multiroom it is a condition of the contract that you leave all your skyboxes able to dial out on the same phone line 24/7, so they can check they are at the same property. If you turn them off at the wall, your effectively violating your contract.

I disconnected my sky box from the telephone line as soon as my year was up i didnt agree with connecting it in the first place.

The only other thing thats happened recently is the wife let a plugged in electrical appliance fall in the sink which obviously tripped the main fuse/breaker (and could have killed her i know). Could this have damaged any circuitry?

 

[Steve]

I disconnected my sky box from the telephone line as soon as my year was up i didnt agree with connecting it in the first place.

You dont have multiroom then.

If you do this on multiroom, they will send you letters threatening to charge two full monthly bills instead of one and a half.

 

[securespark]

Avoid all that hassle & a huge bill by only having Freeview!!

 

[sparkyspike]

It doesn't have to be an appliance that is at fault - it could be fixed wiring. RCD trips are caused by the following-

- water ingress (outside lights/sockets etc)
- fridges, freezers, immersion heaters etc towards the end of their useful life
- damaged wiring (mice, abrasion etc)
- faulty RCD
- accumulative earth leakage caused by many multimedia devices/PCs etc being connected
- some other faulty appliance

My money is on the fridge.

The best way to find out the cause is to have an electrician test the circuits. A cheaper way would be to disconnect appliances one at a time and use elimination. This won't always find the fault and can take a long time even if it does. If it happened at night, try any timed devices such as immersion heaters and also automatic appliances like fridges etc.

Opening a circuit breaker won't necessarily clear a fault on a circuit as an RCD can still be tripped by a neutral to earth fault on a disconnected circuit.

 

[ericmark]

1) I have never seen a main switch trip. Go on fire yes but never trip. So I would assume you are talking about a RCD unit not main switch.
2) Where one RCD is used for many items then small leakage in each can add up and cause an RCD to trip.
3) Switch mode power supplies often have filters on supply to stop spikes and these do have some leakage this would include items like TV, DVD, VCR, and Sky box so these could cause problems when combined with other items which also leak like filtered sockets.
4) The Sky box only really needs to be connected to a phone line to order movies and this is very important with Sky+ where you don't pay for a movie until you watch it so unplugging the phone line could be a sign of someone trying to defraud Sky. But unless these pay to view services are used I would not think they would care.
5) Standby on Sky is a laugh as on standby it still uses 7 Watt even though there was an agreement that all new TV's VCR's etc should be 1W or less. Running they use between 12 and 16W with Sky+ box.
If you compare this to my Free to Air satellite box when on 4W and in standby the watt and ammeter reading are too low to register being less than 1W or 0.001A.

It seems Sky boxes do not turn off supply to LNB while in standby. So if turning all Sky boxes to standby will save enough electricity to power Birmingham and a single 500KVA transformer will power 35,000 Sky boxes and a 500KVA transformer will supply around 100 houses so with around 1/2 million population in Birmingham say average 4 per house then there must be by time we include factories around 100 million Sky boxes in the UK. i.e 2 Sky boxes per person average if we consider what Sky says about switching into standby is connect. And I would think there would be an outcry if all these were causing RCD's to trip.

Mind you I have that feeling that Sky's statement that if we all switch our sky boxes into standby it will save enough power to power Birmingham may be flawed!!!

 

[Steve]

Eric, I couldnt follow that. You shouldnt post such complex theorem after 11pm

 

[flameport]

The only other thing thats happened recently is the wife let a plugged in electrical appliance fall in the sink which obviously tripped the main fuse/breaker (and could have killed her i know). Could this have damaged any circuitry?

Damaged - very unlikely.

However if the RCD had not been tested for a long time, it the mechanism may have become partially stuck or jammed. The appliance in the sink likely created a current imbalance many times greater than the RCD tripping current, so it did trip.
However because the mechanism has now been moved it may have been loosened/unstuck so the minimum current required to trip it now could be less than before.

 

[spoony77]

Ok so this has happened twice today and its not the night-time and barely anything was on (the fridge is a newish one) if you look at this pic its the big RCCB on the left that keeps tripping out.

However if the RCD had not been tested for a long time, it the mechanism may have become partially stuck or jammed. The appliance in the sink likely created a current imbalance many times greater than the RCD tripping current, so it did trip.
However because the mechanism has now been moved it may have been loosened/unstuck so the minimum current required to trip it now could be less than before.

How would i test/repair for this possibility?