Leccy randomly shutting off

[ODB]

Hi there

This is a bit of a weird one. I have moved into a new house and it seems as though the main fuse/switch for the wall sockets trip completely at random.

Sometimes I can make it happen by turning on/off some strip lights I have in the conservatory so I started there.
One time I notced on the light switch for these lights a tiny flash of light coming from inside when turning the light off, so I changed the switch but the situation hasn't improved.

It seems to be worse over the last few weeks since I've had the central heating on, but even then I've come home when I know the central heating hasn't been on and I'll find all the sockets off.

Indeed, this happens when I've been at home with no significant load on the mains (all light switches off etc). I have some basic stuff permanently connected (modem/router/fridge/microwave etc) but nothing I would have thought would trip anything or have wildly fluctuating power usage.

This is pretty much happening daily now, was wondering if there's anything I should be looking out for? I've got one of those modern consumer units under the stairs...

 

[Chri5]

Could you post some details on the fuse board / consumer unit.

Ideally the make, the fuse size and designation (light, sockets, cooker etc) and let us know if the board is a split unit with some fuses working on an RCD and others working from the main fuse cut off.

You haven't made it clear regarding what is tripping off, is it constantly the same fuse / MCB or is it an RCD that managed a bank of MCB's.

It does seem odd that lighting switches are affecting ring main fuses, are you sure the lights for the problem area aren't wired in to a socket circuit via a fused spur box somewhere.

If you are able to take a picture of the fuse board that might help. Oh, and you mention the house is new, does that mean brand new? And if so would it not be simpler to invoke the warranty offered on a new property and get the sparks firm that did the work to come and check the whole electrical installation?

 

[ODB]

Wow, thanks for the speedy reply!

House isn't brand new, maybe 1920's. I'll take some pictures of the unit when I get in tonight.

I have the feeling the lights in the conservatory may be wired in to a socket somewhere, will try to trace the wires as well...

 

[ODB]

OK this is what's under the stairs:

I have circled the switch that keeps tripping...

 

[Cremeegg]

Remote diagnosis can be tricky but I'd suggest starting with the conservatory strip (presumably flourescent) lights. A combination of a high start up current and lately some pretty damp misty weather getting into the fittings could be causing the RCD to trip if they are wired off teh power circuit.

Always a good idea to get your "permanent" power supplies to teh likes of alarms. routers, freezers put on the non RCD side (the right hand side) of your board. Otherwise with a problem like you have and over a weekend if it all trips out you'll have a freezer full of mush.

 

[JohnD]

the RCD is tripping. this is caused by earth leakage. The lighting circuits ar usually not protected by the RCD, since total darkness can be dangerous.

If your conservatory lights go off they are probably, as you say, connected to a socket circuit, hopefully through an FCU fused at 5Amps.

Leakage is most often caused by watery appliances such as kettles, immersion heaters, boilers and their pumps, steam irons.

For a start, UNPLUG (don't just switch of) all appliances except when they are being used.

If your boiler or immersion heater are protected by the RCD, turn them off at their FCU which (if reasonably modern) will have a 2-pole switch.

Look for any signs of water getting into a cable or accessory, especially outdoor lighting, pond pumps, garden sockets.

If unplugging and switching things off cures the problem, try plugging half of them back in for a day. If the trouble immediately restarts, you have probably included a faulty appliance. If not, unplug the first lot and plug in the second lot.

Do a search on "RCD nuisance tripping" it is a very common problem.


What circuits have you got on the RCD side of your consumer unit?

Don't go poking your fingers into those holes - they should be closed off with blanks. I imagine Wylex NH blanks would cost you about 50p each at an Electrical Supplies outlet. the absence of blanks is not a good sign of professionalism in the person who fitted it.

 

[ODB]

This is what puzzles me, it shuts off even when nothing else is on, halfway through the day (not at the same time each day).

 

[ODB]

Many thanks for all your comments, this has given me plenty of things to look into on my day off tomorrow!

 

[Chri5]

Here's a link for the Wylex blanks

http://www.tlc-direct.co.uk/Products/WYNS00.html They are 30p each. They clip in and will prevent fingers poking in holes, that might bite back

To id where the lights in the conservatory are fed from turn off all the MCB's and by simple process of elimination your fine which MCB supports the wiring that feed them.

Since these are suspect, I'd leave the MCB off and see if the normal trip routine stops. If they are on a fused spur, which is a must if they feed via a socket circuit switch that off and isolate just the lights,

Again waiting for a 12/24 hour period and seeing if the phantom trip of the RCD stops.

Please report back and please be careful.

 

[Steve]

This is what puzzles me, it shuts off even when nothing else is on, halfway through the day (not at the same time each day).

How old is your fridge?

What you should understand is the switch you have circled is a very sensitive earth leakage monitor. Its primary purpose is to protect from electric shocks. It takes 50mA to kill - thats milli-amps. That device is rated at 30mA.

However, it is common for older fridge and freezer compressors to develop high earth leakages as their carbon brushes wear away and create conductive dust. This can happen in any motor or pump too.

It is also common in heating elements for the insulation to break down and realise a leakage to the earthed sheath of the element.