Socket circuit fault - Can an electrician help me?

[Dillz]

I have a strange problem with my socket circuit. Occasionally the circuit trips. It only happens during the Winter, has only happened in the evening and the the only consistent factor is that the central heating is on when it happens, althought the gas boiler is on a separate circuit to the sockets. When the circuit trips it won't switch on again until the following morning. It can happen a couple of times in a week and is then fine for a fortnight! I have replaced the MCB (the limit of my know how!), tried unplugging all appliances in the circuit all to no avail. It has only happened since a new heating systen was intalled a couple of years ago. Would a hot water pipe touching a cable cause this?

Unless I call an electrician out of hours then the circuit would be working fine when he arrives. Would it be worth me calling an electrician when it is working? Would he be able to test each section of the circuit to identify a fault if the circuit was working OK? Is an electricians test equipment more sensitve than whatever threshold is tripping the MCB?

Any advice appreciated. Thanks

 

[Dillz]

I should also mention that I have an RCD that also trips when the MCB trips but I can switch this back on providing I leave the MCB off for a few hours / overnight.

 

[bongos]

More info needed!

Have you got an outside light/socket spurred from the ring circuit? If the MCB & RCD are tripping simultaneously then I believe this could signify a L/E fault. What is plugged in on this circuit? Do you only have one RCD for the whole CU? It's also possible that if you are running alot of appliances (which you would tend to in the evening in winter) that the combined earth leakage would be enough to trip a 30mA RCD.

Would it be worth me calling an electrician when it is working? Would he be able to test each section of the circuit to identify a fault if the circuit was working OK? Is an electricians test equipment more sensitve than whatever threshold is tripping the MCB?

An electrician will be able to insulation resistance test the faulty circuit to see if there is any short or breakdown in insulation between L/N/E. They should be able to locate the fault although intermittent faults like this can be a nightmare to diagnose. They will also be able to ramp test the RCD to make sure that it is working within the correct tolerances.

 

[JohnD]

Earth Leakage faults are most often caused by watery appliances such as kettles, immersion heaters, tea urns... and boiler, their pumps and motorised valves.

Look carefully for signs of water leakage around the pump, valves, thermostat, cables. You may not be able to safely look inside the boiler casing (it may be room-sealed for safety and need a Gas Safe heating engineer) but if you try switching off the DP switch (not the boiler controls) or pulling the plug for 24 hours, you may detect if the fault stops happening. You can also isolate the power and look inside the Cylinder Stat and Room stat covers in case there is a loose wire.

Also look for signs of leaks around rad valves or underfloor pipes, they may be dripping onto a socket or cable. This sort of leak may start and stop with temperature changes, and may take some hours to dry out.

Sometimes a hot pipe can be installed pressing against an electric cable, and yes, this softens and damages the PVC insulation and can lead to live contact and unpleasant results. This usually occurs when neither plumber nor electrician has positioned their part carefully, and the pipe and cable are tight under the floorboard. If you like to take up floorboards you may be able to trace it. It will probably be fairly obvious which boards have been taken up. Have a good sniff for any smell of burning or sounds of sparking (it can be very dangerous). A professional insulation test would have a fair chance of finding it if the cable has been damaged like this.

BTW you can always turn the heating up after the electrician arrives

p.s. sorry this sounds vague... intermittent faults are especially hard to find

 

[martinxxxxxx]

When the circuit trips it won't switch on again until the following morning.

If the RCD will reset but won't with the MCB reset and they both pop out together then it is my opinion that you have more than a build up of earth leakages here. You, in my opinion have an intermittent short circuit - phase to earth.

A simple insulation resistance test will identify the circuit where it is happening. Splitting the circuit and testing half at a go should allow the electrician to find it in a jiffy.

It does sound as if the short may be caused by water as it takes overnight to dry out. Even so there is probably enough carbonisation where the short has occurred to still still give a low IR reading even when the fault is not evident.

This is a fairly bread and butter job for an electrician, but as a someone with out experience or tools for the job it will be difficult to get to the bottom of,

Martin

 

[ban-all-sheds]

This is a fairly bread and butter job for an electrician

Assuming he's a real electrician, not an NVQ DI who would have had zero training (formal or informal) in fault finding and would not have needed to demonstrate any competence or experience in it to get registered.

 

[Dillz]

Well thanks for the replies. The circuit tripped again this evening so I was on a mission and I set about making sure that everything I could possibly disconnect from the circuit was disconnected. I had previously unplugged all the appliances but forgot about a fused spur to a bathroom macerator, a burglar alarm and the power supply to the clock on the gas cooker.

When I pulled out the gas cooker, which is plugged into a 13amp socket down the back of it I found that there was condensation from the elbow joint of the cold water pipe dripping directly onto the socket. (the pipe comes from under the sink and then goes up the wall directly behind the cooker) Unplugged it and hey presto the circuit could be switched back on again.

I am still going to have to get an electrician in though as I also found a 30amp cable just dangling from the wall with a bit of insulating tape round the end, fortunately the 30amp circuit is switched off and will obviously stay that way until it is made safe.

As a temporary measure I now have the gas cooker electrics plugged into an extension lead well away from the drippy pipe.

Thanks for the replies I was relieved to find the problem - would have felt a bit stupid to have an electrician pull out the cooker and point out the obvious!

 

[ColJack]

it's a plumber you want, not a sparky..
the electric is staying in the cables where it's supposed to be.. it's the water that's being naughty and escaping..

 

[ban-all-sheds]

I found that there was condensation from the elbow joint of the cold water pipe dripping directly onto the socket.

Get some pipe insulation.

I am still going to have to get an electrician in though as I also found a 30amp cable just dangling from the wall with a bit of insulating tape round the end, fortunately the 30amp circuit is switched off and will obviously stay that way until it is made safe.

You really should be able to make that safe yourself - does the cable come directly out of the wall, or from a cooker outlet plate?

If the former then put a junction box on the end and fix it to the wall, if the latter then just remove it.

It's notifiable of course, but.....

 

[ColJack]

It's notifiable of course, but.....

what a stupid comment BAS..
since when has making something safe that does not include any intallation been notifiable?

in fact doesn't it expressly say...

(b) replacing a damaged cable for a single circuit only;
(c) re-fixing or replacing enclosures of existing installation components, where the circuit protective measures are unaffected;
(d) providing mechanical protection to an existing fixed installation, where the circuit protective measures and current carrying capacity of conductors are unaffected by the increased thermal insulation.

is not notifiable?

 

[mikhailfaradayski]

deleted after reading the OP second post properly.

 

[martinxxxxxx]

This is a fairly bread and butter job for an electrician

Assuming he's a real electrician, not an NVQ DI who would have had zero training (formal or informal) in fault finding and would not have needed to demonstrate any competence or experience in it to get registered.

Yes i agree with the above, though it is a bit long winded to spell out in the context of what I was saying. In fact the bit Bas has quoted; I only added because there are those who believe the cost of employing an electrician is to be avoided. Where as I maintain that the right experience and training will get to the root of the matter more quickly.

So use a recommended electrician if poss and avoid pretend ones who cannot show you qualifications and experience stretching back a few years. Ask for a run down of their quals when past and their work history. Then you should be safe to let them investigate the fault for you.

 

[ban-all-sheds]

what a stupid comment BAS..
since when has making something safe that does not include any intallation been notifiable?

“building work” has the meaning given in regulation 3(1);
.
.
“controlled service or fitting” means a service or fitting in relation to which Part G, H, J, L or
P of Schedule 1 imposes a requirement;
.
.
“electrical installation” means fixed electrical cables or fixed electrical equipment located on
the consumer’s side of the electricity supply meter;
.
.
Meaning of building work

3.—(1) In these Regulations “building work” means—
(a) the erection or extension of a building;
(b) the provision or extension of a controlled service or fitting in or in connection with a
building;
.
.
Giving of a building notice or deposit of plans

12.—.
(1) . .
(2) This regulation applies to a person who intends to—
(a) carry out building work;
.
.
(5) A person who intends to carry out building work is not required to give a building notice or
deposit full plans where the work consists only of work—
(a) described in column 1 of the Table in Schedule 2A if the work is to be carried out by a
person described in the corresponding entry in column 2 of that Table; or
(b) described in Schedule 2B.

And Schedule 2B does not list installing a JB as exempt from notification.

in fact doesn't it expressly say...
(b) replacing a damaged cable for a single circuit only;

Adding a JB is not that.

(c) re-fixing or replacing enclosures of existing installation components, where the circuit protective measures are unaffected;

There isn't an existing enclosure.

(d) providing mechanical protection to an existing fixed installation, where the circuit protective measures and current carrying capacity of conductors are unaffected by the increased thermal insulation.

Does a JB count as mechanical protection?

 

[ColJack]

there was an existing enclosure, whatever was on the end of that cable..
it doesn't say existing enclosure anyway..

on the basis that you are putting an enclosure onto the end of an existing ( and probably unsafe ) cable hanging out of the wall, I'd say it doesn't apply..

can you really see him getting done for making a cable safe?

he doesn't even know if the thing is live or connected at the other end..

it'll look good when he pays the £200 to have the LABC guy come round to test and say.. " yeah, it's disconnected at the board and cut off.. "

and...

Does a JB count as mechanical protection?

yes it does.. otherwise we'd still be able to just stuff terminal blocks up into the ceiling without putting the connections in a box..

 

[ban-all-sheds]

there was an existing enclosure, whatever was on the end of that cable..

Sticky tape is not an enclosure.

it doesn't say existing enclosure anyway..

"re-fixing or replacing enclosures"; you can't re-fix or replace something that wasn't already there.

can you really see him getting done for making a cable safe?

No, and I never suggested that he would or might.

and...

Does a JB count as mechanical protection?

yes it does.. otherwise we'd still be able to just stuff terminal blocks up into the ceiling without putting the connections in a box..

It provides mechanical protection along with other things. Adding one is not only providing MP, it is adding electrical termination.