My Mains fusebox keeps tripping at between 3am and 6am every

[JohnD]

* Can someone explain why the main switch trips and not the individual circuit breakers!!!!!!

It is not a main switch; it is an RCD (which can be used as a main switch but this is not the best design).

By "Individual Circuit Breaker" you mean an MCB. An MCB will be marked "B6" B16" B32" etc. that means it is designed to support a circuit carrying a max load of 6Amps, or 16 amps, or 32Amps. Loads above this will cause the MCB to trip. The greater the overload, the faster it will trip. A short circuit will make it trip very fast.

An RCD is not an Overload device. It is usually rated "30mA" or sometimes "100mA" (other ratings are available for different purposes). That means that if it detects an earth fault of 30 milliamps, or of 100 milliamps respectively, it will cut all power passing through it, usually within 0.03 of a second or less. this is fast enough to prevent you being injured or killed by such a fault.

The fault arising in the thread is an Earth Leakage Fault. This can be caused by e.g. water getting onto connections; or a faulty appliance, or a mouse gnawing a live cable, or someone touching a damaged cable.

 

[Softus]

* Can someone explain why the main switch trips and not the individual circuit breakers!!!!!!

You're missing the point that the main switch is an RCD. This means that it will detect a current leakage fault, whereas each MCB will detect an over-current fault.

 

[JohnD]

tee hee!

Anyway, RCBOs would have avoided this problem

 

[sm1thson]

* Can someone explain why the main switch trips and not the individual circuit breakers!!!!!!

the main switch is an RCD, the breakers are MCB.

the breakers trip if too much current flows such as too many things turned on or a short circuit -their job is to trip before the cable sets on fire.

the RCD detects that there is an imbalace in the current leaving the RCD and the currant coming back so i.e there is a leakage somewhere such as electricity escaping to ground through some condensation -their job is to cut the supply so electricity doesnt find its way to earth through you.

-I think theres more (and better) info on RCD's and MCB's in the wiki. (edit-and above because i was slow posting lol)

 

[Softus]

Anyway, RCBOs would have avoided this problem

You just couldn't let it lie!

 

[diablo1952]

+++ big quote removed - Mod Rupert +++++

Chaps I have now installed a DP to isolate the outbuilding and will switch this off tonight to see if the outbuilding is the problem. Your suggestions have been very helpfull and I have learnt a lot. Will keep you posted tommorrow
Very best regards
Paul

 

[EddieP]

Can we rule out an under floor electric heating fault ? I ask because of the fluctuation in the time of the fault. As I understand it, with an OCR timer on a cold morning the heating kicks in earlier than on a warm morning in order to reach the set operating temperature of the floor by the required time.

 

[diablo1952]

Can we rule out an under floor electric heating fault ? I ask because of the fluctuation in the time of the fault. As I understand it, with an OCR timer on a cold morning the heating kicks in earlier than on a warm morning in order to reach the set operating temperature of the floor by the required time.

thanks for this

but I dont have underfloor heating just a normal gas boiler
Paul

 

[fireman22]

had same problem on my mates house, set rcd tester to half trip could not make it trip with everything on. unplugged everything including fidge freezer when he went on hol's. tripped when he was away so changed rcd and now all fine.

 

[securespark]

Trouble is, a DIY'er cannot test an RCD...

 

[Steve]

Trouble is, a DIY'er cannot test an RCD...

you say that . . . however, a few lamps of different ratings, wired between live and earth will give you an approximate idea of the trip point

 

[sm1thson]

Trouble is, a DIY'er cannot test an RCD...

you say that . . . however, a few lamps of different ratings, wired between live and earth will give you an approximate idea of the trip point

-thats why they call you crafty then!?!

 

[diablo1952]

had same problem on my mates house, set rcd tester to half trip could not make it trip with everything on. unplugged everything including fidge freezer when he went on hol's. tripped when he was away so changed rcd and now all fine.

We isolated the outbuildings last night. and at 1.15am the RCD tripped with only 2 60w lights and a tv on standby, sky box on standby and dvd on standby. when I tried to reset it it would not reset, after 60 seconds it reset and has not tripped so far. !! Should I change thr RCD anyhow !!!

 

[JohnD]

?All your other appliances, especially the washing machine and kettle, were actually unplugged? Your immersion heater, boiler, electric shower, power shower, cooker and outside lights were turned off with DP switches?

Tonight, unplug those stand-by appliances as well.

Next time it trips, turn off all the MCBs and see if it makes any difference (it might, it might not),

What is the brand and age of your RCD (and consumer unit)? Is it marked "30mA" or "100mA?"

(guys, I have a feeling this gentleman may be in the right frame of mind to splash out on some RCBOs )

 

[diablo1952]

+++ big quote removed - Mod Rupert +++++

The RCD is marked at 100ma I will unplug everything I can apart from the two freezers and fridge (obvious ) what I still dont understand is why it never trips in the daytime. I have ruled out condensation as I fitted a DP for all the outside power sources. At night we have the following still connected :-
The main chest freezer/The 2nd Freezer/the fridge/1 60w living room light
1 60w landing light/Internet 4 port router/ we have switched off the boiler and at the moment only use it when we need it.