Mains trips randomly

muckybutt

Old Wylex unit

I would imagine more likely than not you have an intermittent Neutral - Earth fault.

It wont be an over current fault or a short circuit fault as the MCB's are not tripping unless they are kippered !

Ideally you want a full inspection doing to see if that flags up the fault, then from there rectify the fault or faults and then get the board swapped for something a little more up to date.

The fault its self could either be a wiring fault or an appliance fault so you might need to get things like your microwave - oven - fridge etc PAT tested as well, I have come across fridges and freezers tripping RCD's a few times over the years.

shays_mum

This happened to my mum recently, finally managed to pin it to a new smart price asda kettle that was shorting the place!!:eek:

ValHaller

pcgtron wrote: »

Picture of fuse board. The mains switch on the right trips, but the rings are all still on

Switch on the right is a RCD.

The fuse board looks tatty, but changing it will almost certainly not fix the problem unless it is an issue with the wiring inside. It is actually doing its job fine. Your problem is to isolate the source of the fault.

It could be any circuit, I would tend to suspect the immersion element or cooker elements. But it could be anywhere - including N-E shorts as mentioned.

pcgtron

The cooker is less than a year old, the immersion ring doesn't have anything on it. The old owners fitted a combi boiler and cut the pipes to the old water tank which is still in the loft. I have yet to find anything on the immersion ring

Ectophile

That's definitely an RCD main switch. The "test" button and the "30mA trip" label are the giveaways.

The chances are that some appliance is going bad. Most likely, it's either something with a motor (which could include the central heating system) producing current spikes, or else something with a heating element (e.g. cooker or immersion heater) with failing insulation.

It could also be damp in the electrics causing a higher than normal leakage to earth.

It's going to be a sod to fault-find. Either try leaving un-needed circuits switched off to try and isolate it, or get in a qualified electrician with all the test kit.

cyclonebri1

My apologies re the RCD switch, when someone says they don't have one gullible here accepts it,

I should have expected that. Once when plasterboarding a new extension with the power off, I managed to put a nail edgeways across all 3 conductors of a ring main.

Powered up, didn't take mains out but did blow elec boards main fuse:o

And yes, it was mid winter and 4.00pm:eek:

Moss5

I had a similar problem in my house. I replaced the 63A RCD with a 100A main switch and each MCB with an RCBO.

http://www.electricalcomponentsdirect.co.uk/acatalog/ECD-100A-DP-ISOLATOR-83.html#SID=2



http://www.electricalcomponentsdirect.co.uk/acatalog/RCBO-ECD-1E-1PB32-B-curve-32A-RCBO-30mA--4.html#SID=2



An RCBO provides earth leakage protection/press-to-test facility/over-current protection for each circuit.

A faultcondition will trip just the faulty circuit, not the whole house.

I may still have a faulty circuit to fix, or faulty appliance, only time will tell.

fluffpot

since the fault is very intermittent it might not show up on testing and could be an appliance which is disconnected when the tests are carried out anway.... so I'd be inclined to recommend a board change to all rcbo's (circuits tested of course!)

Then if the fault occurs again, at least it can be narrowed down to an individual circuit and investigation proceeds from there

pcgtron

Any idea of a rough price of changing the board?

[Deleted User]

I think it's well worth changing the main RCD first. When they're old and knackered they can start dropping out at random for no reason at all.

I wouldn't be inclined to read too much into the fact that it's only the main breaker going either. If there's a transient surge causing the problem, it may be the fastest acting breaker that drops out first, not necessarily the one feeding the individual circuit. If transients are large enough and sudden enough, the effects can be quite peculiar sometimes.

If you don't have the expertise or test gear, you're going to be calling someone in anyway, so it will be for them to sort out.

Also consider putting your freezer on a separate circuit of its own, protected by a good old fashioned fuse, rather than sensitive circuit breakers.