Why is the 80A trip switch being triggered

[Nick Thorley]

A couple of times now I have returned to home from work and found the power is off. On checking the electrical cupboard I found that the main 80A trip switch had tripped but the individual circuits - lighting, sockets etc hadnt and were fine. Could anyone suggest why the main trip switch should trigger - it has happened with no-one in the house and no large electrical items running except a sky box and fridge.

It has done it a few times now

 

[alpha spark]

Is it a rcd does it say on it 100ma or 30ma on I'm guessing it does it's a rcd and likely there is an appliance like a fridge or washing machine that's causing it to trip

 

[Zeespark]

Where in the UK are you Nick?

AndyGuinness

 

[SLIPSHOD & SLAPDASH]

If its an appliance causing this (even if it is plugged in but not turned on) its usually something with water. Firstly the kettle, then an immersion heater, steam iron, washing machine & dishwasher- thats the order i would check

On the other hand it could be vermin chewing your cables.

 

[Nick Thorley]

I am in Staffordshire

Where in the UK are you Nick?AndyGuinness

---------- Post Auto-Merged at 14:59 ---------- Previous post was made at 14:58 ----------

I will check those applicances suggested. Lets say it was a kettle - wouldnt it trip the socket circuit first before hitting the large 80A main RCD?

 

[SLIPSHOD & SLAPDASH]

No, if its an earth leakage fault.

 

[paul b b]

Hi Nick. Could you post a pic of your consumer unit?

 

[christhe]

If its an appliance causing this (even if it is plugged in but not turned on) its usually something with water. Firstly the kettle, then an immersion heater, steam iron, washing machine & dishwasher- thats the order i would checkOn the other hand it could be vermin chewing your cables.

Then the boiler pump and if its been pouring with rain where you live check any outside lights dont resemble fish tanks full of water!

 

[steptoe]

what you need to understand is that the main switch [RCD] is rated to carry 80A,

it will in fact 'trip' if there is a fault to earth of 0.03amps , so, as you can see, much much smaller than the 32[or30] amps that the socket breaker is rated at.

 

[OnOff]

It sounds like you have an older installation where an "upfront" RCD protects all the separate circuits against earth leakage. It's not ideal as you have found as a fault on one circuit takes out the lot as you are finding out. First thing is to determine whether it's an appliance or a wiring fault. Could be one of MANY things, dodgy fridge, boiler, a loose connection in for instance a socket etc. Why not have someone local to you on here quote for / do an EICR - Electrical Inspection Condition Report. You may also want to consider upgrading the consumer unit to minimise such inconvenience.

 

[Doc Hudson]

A couple of times now I have returned to home from work and found the power is off. On checking the electrical cupboard I found that the main 80A trip switch had tripped but the individual circuits - lighting, sockets etc hadnt and were fine. Could anyone suggest why the main trip switch should trigger - it has happened with no-one in the house and no large electrical items running except a sky box and fridge.It has done it a few times now

The switch is a 30ma or 100ma earth leakage detection device, also called an RCD. It is tripping due to a very small current, less than half an amp flowing to earth. Probably a faulty appliance rather than faulty wiring. Doc H

 

[monkey5]

like slips says you must unplug the appliance to eliminate it not just turn it off at the switch, as if its a neutral to earth fault (which were assuming its an RCD/ELCB tripping - post a pic and we can tell straight away as long as its not too late as there will be a few members with the beer goggles on later id have though!) the faulty appliance could still cause a trip.

 

[Sharpend]

Why don't you just unplug everything other than fridge/freezer for one day, if you get home and find it has tripped then you know that it is one of those appliances, if it has not tripped then the following day leave fridge, freezer and kettle plugged in, each day add a an appliance until you get home and find it has tripped again. Failing this get your appliances PAT tested to eliminate them. Would defiantly put it down to suspect appliance as opposed to any wiring issue, although not impossible as someone has mentioned rodent damage is possible.

 

[OnOff]

As you go to unplug the individual appliances, and BEFORE you switch them off (via the socket switch) check they're not loose i.e. the socket isn't loose. Might be a loose connection in the back of one. My most recent recollections:

- loose neutral wire on a spur socket for a washing machine.

- a kettle under a VERY low wall unit. Seems that occasionally the lid on the kettle wasn't being pushed in properly and copious amounts of steam was condensating.

- dishwasher element. Would heat up then trip the RCD. Actually took the time to show my son by doing an IR test with the removed element in a jug of cold water then in a jug of boiling water. In effect a contraction / expansion issue. You haven't put any nails / screws in wall lately for pictures etc have you?