mains circuit and rcd tripping

[BigMacUK]

Brief history, the house was built circa '99 and I've lived here since '01. There has been no electrical work ( such as changing sockets / light fittings ) for several years.

Twice now, I've had the rcd and 1 circuit trip where I've lost power to the mains sockets downstairs in the house. That is to say, upstairs mains and the lighting circuits are all fine.

I think the important point to cover is, I've bought no new appliances recently and on both instances was doing nothing out of the ordinary.

The first incident was on Sunday, I was playing games on PC and the power tripped out. It wouldn't re-engage at the fuse box, tripping immediate when I reset the fuse. Went around the various mains sockets turning them off. Reset the fuse box, and turned the sockets back on. Everything back to normal.

Tonight, I was in bed. Such things as the TV were in standby mode, the PC humming away idle, monitor off and such. Followed the same drill as Sunday, sockets off - reset fuse - sockets on, and now I'm back and able to post this message.

I remember years back, the "fun" when my mother would plug in the iron and not always but often the circuit would trip needing resetting. I can only emphaise in both cases nothing like that was happening, certainly not while I'd been in bed for couple hours - I live alone!

Obviously I have concerns! It's one thing to lose power when the supplier has a fault, but something internal to the house tripping it? I don't understand what's going on and need suggestions here on ways forward.

Thanks.

 

[Paul Barker]

No expert by any means but:-

too many devices with small leakage current from emi filters add up to >20ma which in time can trip an rcd. Such items as microwave washing machine (anything that otherwise would send emi back down mains has to be filtered the filter causes leakage current.

your playstation will have such a filter as liely to protect itself as the mains (works both ways).

Secondly kettels and other wet environment appliances can cause leakage.

There is a case for seperate rcd protected radials to kitchen appliances, non rcd radial for freezer, and computers (games consoles).

 

[JohnD]

you use the words "fuse" "RCD" and "circuit"

What is the thing that is tripping? Is it more than one thing?

If you can post a pic of your consumer unit, and identify which things(s) is/are tripping, it will help.

It will also be useful to have a wide-view pic showing your supplier's service head, the main fuse and earthing wires , meter and consumer unit to get an idea of your installation.

If you UNPLUG (not just switch off) your washing machine and any other suspect appliances, it will probably make a difference. Then you can plug them back in one at a time for a night night and see if one of them brings the fault back. If you have an oven or water heater on the socket circuit, unplug it or turn off at the big switch at the wall.

Also look out for any external lamps, sockets or garden equipment that comes off that circuit. It might be getting wet from rain. Also look for any signs of mice gnawing the cables, including under the floor or in a garage or shed.

 

[BigMacUK]

Thanks for the feedback so far. I may not know the right terms of reference and so may get them wrong, sorry for that. Also not in a position to post a picture just now but will see about it later if necessary.

To describe the "fuse box" it lives above the front door in the house. Drop down flap which has a series of switches. On left side, a couple of red and to the right I think was green, marked RCD. In between there are a series of switches, that I consider to control power to various "circuits". Through trial back in '01 I marked them as being for lighting circuits, and the wall sockets for cooker, downstairs & upstairs.

When things are working, the switches are in the up position. This morning, when the power tripped, all were up bar two of them. The switch I marked for downstairs wall sockets and the RCD.

After turning off various wall sockets, I returned the RCD to up position, the "downstairs socket" switch to up position. Then proceeded to turn back on the appliances had turned off at their wall switches in kitchen and living room.

When I left the house this morning, some 5 hours later all things still running. But then, it had ran from Sunday even till this morning fine. Prior to Sunday, I've had no troubles since moving in back in '01.

 

[JohnD]

The Main Switch is generally twice as wide as the "switches" for individual circuits.

These "switches" are called MCBs (Miniature Circuit Breakers). They are marked with numbers indicating their rated load current (e.g. B06 for a 6 amp lighting circuit, B32 for a 32 amp socket circuit, B16 for an immersion heater). If there is a current overload exceeding the rating it will trip the MCB.

The RCD is usually two or more times wider than the MCBs. It will have a button on it marked "T" or "Test" and will say "Press T Quarterly to test" (if an RCD is not regularly tested it may stick and fail to trip when needed). The RCD does not trip on current overload, but on a leakage of current to earth, typically from a water leak or a damaged cable.

I understand you to say that both the MCB and the RCD have tripped. this suggests severe damage, most likely to a cable, e.g where a nail or screw has put put through a wall, or occasionally where rodents have gnawed through the insulation. It is rarely caused by water leaks since the power available is enough to boil away water. It could also be caused by a loose connection allowing wires to come into contact inside a socket.

A fault significant enough to trip a 32A MCB will be quite big (equivalent to three or more electric toasters), there may be sparking or wires glowing red hot, and there may be smoke or smells of burning. If you cannot see this at any of your sockets, it may be under the floor. It can also happen if the flex to an appliance is crushed, e.g. if the washing machine has been put down on its own cable, although this would often also blow the fuse in the plug.

If you have a supply to a shed, garage or outbuilding on the circuit, look for damage or bad connections there. If are able to turn off outbuilding supplies until checked, it may help.

If it is not a simple loose wire in a socket, or nail through a cable, or damaged flex,you will probably not find it easy to trace and repair yourself. While you are looking for the fault, start asking round friends and neighbours for a recommended local electrician.

When phoning, ask first if they are a member of a "Self Certification Scheme", ask which one, and how long they have been a member (write this down, as you can check it). Although not a perfect test, this will tell you if they are sufficiently qualified and approved to install in houses without needing their work to be inspected and tested by the local authority, and they will issue documentation for work they do, showing test results.

Note: If the breakers stop tripping, this does not indicate that the fault has magically corrected itself. it means that the wires have burnt away and are no longer touching, but are still dangerous.

If you have any suspect appliances, pull out the plug. Don't rely on the switch.

In the interest of safety, it would be best to leave the faulty circuit "off" at the MCB until the fault is found and corrected. Also check the batteries in you smoke alarms

 

[BigMacUK]

Hi Guys,

I've had opportunity to take a picture of what I consider to be the "fuse box". One of these days I'll know the right term!

This morning, all switches were in the up position bar no 5 and the RCD, which were both down.

For completeness of info's that I can give. Switches 2 & 3, are for the downstairs and upstairs lights respective. Switch 7 marked for the cooker. with 6 and 5 marked as sockets. Whilst didn't note it at the time, I believe 6 to be upstairs and 5 downstairs wall sockets. Going by your description of the B6 / B32, that would tally up as well. Great, i've learned something new!

 

[Adam_151]

Generally these days we call it a 'consumer unit (CU)', the term also can be used to refer to one of the old types (often a wylex standard: http://www.tlc-direct.co.uk/Images/Products/size_3/WY304.JPG ... also made in brown) which took rewireable fuses ( http://www.tlc-direct.co.uk/Products/WYR5.html ) although cartridge fuses (bigger version of what goes in a 13A plug were available and MCBs could be retrofitted a few years back)

[You can still get carriers for the cartridge fuses for modern boards, but they arn't often used, but they have their uses from time to time]

You one you pictured is a DIN rail based CU (the DIN rail is at the back and the MCBs clip onto it) its also a split load board as the RCD protects only some of the circuits (the three 6A ones are *not*on the MCB, this is normal, don't normally put lights on RCD)

It might also get called a distrubution board (DB) or just board for short, generally CU is prefered since it implies a special type of distribution board (one intended for domestic and other light usage applications)

We try not to call it a fusebox as there arn't actually any fuses in it, and that conqures up images of the old type of CU that actually did have fuses in it

 

[JohnD]

p.s. I just remembered to say...

A wiring fault in a Ring Circuit (as used for most UK sockets) can continue to work even if there is cable damaged or burned through, so don't assume that it is safe just because it still works. However, your friendly local electrician can quickly track down the area where the damage is, even if it is not visible.

 

[BigMacUK]

Thanks once again for the information.

Taking folks advice, I've let my fingers do the walking, and phoned a company from yellow pages. The advert has logos for such "NIC EIC" and makes claims to have been in the business for 30 odd years.

The guy is due to call around in the morning. Little concerned as it was mentioned could be 5 minutes, an hour or all day!! I've seen guys test kit in the office for health n safety purposes, some portable appliance test or so. So I'm full of curiosity as to what will happen tomorrow and how fault will be tracked down.

In my trade, the one word I hate to hear is "intermittent" when talking of faults. As this has happened twice, inside of 36 hours, yet I've lived here little over 6 years with no problems.

Is there any advice for how tomorrow should be tackled?

 

[JohnD]

buy some biscuits

boil the kettle and make him tea before the power goes off

keep the freezer closed

make yourself sandwiches for lunch in case the cooker is still off

take an interest wthout standing over him

find out the charging structure before he starts

be aware that he might have to get at wires under the floor or in the walls, and he will not be an expert plasterer or carpetlayer so you may need to make good afterwards.

 

[pbar]

.....and he will not be an expert plasterer or carpetlayer so you may need to make good afterwards.

That's one of the best pieces of honesty and advice I've seen on here.

 

[BigMacUK]

Hi guys.

He has been, and gone. The tests he carried out were all based from the consumer unit. The various circuits he said were "ok", and testing from there showed the cabling and the appliances plugged in were fine. He did mention the cooker, which was cabled into 7, was a low score of 3, and as it hadn't tripped, nor was it active doing anything during either incident he didn't consider to be a problem as such.

When he tested the RCD itself, he said it was faulty. Something to do with it tripping instantly and he mentioned some scores. Think it was 0, and eventually went to 49 after several tests. This in his opinion warranted a replacement RCD.

The consumer unit has spare slot, as can see in bank 4 of the picture earlier. Therefore he made use of this.

Think he said the alarm was in slot 8, so moves this over to slot 4 and introduced a new mcb into slot 8. Into the new mcb, he's split up some of the house power sockets that were being serviced by 5.

To be honest, I'm a little confused by the wiring now, but he showed that the new number 8 was power for downstairs.

The sparky couldn't advise what the bill would be for the work, other than time for travel / on the job and parts, to which I'd get an invoice in the next few days.

Does this marry up to folks expectations? With folks thinking there is cable damage I'm wondering why he didn't think so and only worked from the consumer unit.

 

[BigMacUK]

Ok - so i got real curious and did some quick tests.

8 - downstairs sockets.
7 - cooker
6 - shower
5 - upstairs sockets.

From this, I can but deduce my former information was inaccurate. That is, the downstairs and upstairs mains sockets must have all been from 5.

 

[JohnD]

I'd suggest you label up the CU circuits for the future.

I find you can make a neat label strip like this:

Buy a roll of white vinyl tape (about 20mm wide) and a fine or medium fibre-tip permanent marker

Measure and cut off a length of tape that will fit on the CU above (or under) the MCBs without obstructing the numbers

Stick it to a clean, hard surface like a laminate worktop

Measure and mark off divisions

Inside the block for each MCB, write (e.g.) B6 upstairs lights" "B32 Cooker" etc

Draw a bright green line along all the divisions that are controlled by the RCD, and a red line for those that are not.

When finished, peel the tape off your worktop, wipe the CU clean and stick the strip of tape neatly into place.

This will save guesswork or relying on memory next time you need to isolate a circuit or identify a fault.


Verify your labelling by turning them all off, then, with a light or a radio or something turned on in every room, turn them on one at a time and verify what comes on.

You might wonder why I don't suggest writing on the strip on the CU? it's because it's difficult to write clearly and neatly in such an awkward position, and if anything changes, you can easily mark up a new strip of tape.

 

[BigMacUK]

Hi John

The flip down door has a chart on it that I'd written on previously in pencil, back in '01 when bought the place. The notes made at the time were enough to highlight the circuits for lights upstairs and downstairs. At the time I marked 5 & 6 as "sockets". I must have figured then to get power off for all sockets needed both off; and in the time since believed that 5 is downstairs and 6 upstairs only to have that corrected today!

But rest assured, they have been labelled up accordingly - and the "quick tests" i mentioned earlier, were exactly as you've suggested. Turned off and had one on, then went around to see what i could use.

The left hand set aren't covered by RCD, so that's the lights and alarm ( 1 to 4 ). The right hand set are, ( 8 - 5 ), that being downstairs sockets, cooker, shower and upstairs sockets.

Did a bit google, and found the RCD is about £36 from some folks and the MCB about £5. So, thinking I may get invoice £120-140 or so.