Domestic circuit tripping

[NigelDent]

Dear all,

I have had a new kitchen fitted and I am having spurious trips on a single circuit. The trip is not when an appliance is running and tends to be late in the evening or through the night and it is not happening every day. The trip takes out the RCD and the MCB but allows a full reset straightaway. The circuit has on it:-

Dishwasher (new) on an isolation fuse switch

Washing machine (old) on an isolation fuse switch

Velux skylight (new) on fuse without an on/off switch

Extractor hood (new) on an isolation fuse switch

Electrics for gas hob (new) on a plug switch

Microwave plugged into socket

Digi radio plugged into socket

Kettle plugged into socket

Toaster plugged into socket

LED underlights on isolation fuse switch

Dining room radio plugged into socket

The electrician who carried out the work has been back to our house & isolated everything and checked the current and earth and the circuit is clear.

Yesterday (Saturday) was the worst day so far ! we started the morning with everything connected and the fuse blew 15 times from 10.30am to 1am, each time I removed an appliance from the circuit until the last time there was nothing on the circuit at all apart from a dining room plug socket switched in the on position but no plug plugged in (didn't spot it until this morning).

Today (Sunday) fuse blew when turning washing machine isolation switch back on (1pm)  and then again 30 mins later.

The last thing to isolate yesterday was the extractor hood, with the hob electrics before that.

This has been happening now for 2 weeks and we cannot get to the bottom of the problem.

Any help or advice would be much appreciated as this is starting to effect our day to day life as we have to keep resetting the fuse & turning everything back on.

Many thanks

Nigel

 

[ProDave]

Did the "electrician" do any insulation resistance testing?  did he unscrew any of the accessories for a look?  Most likely a trapped wire that has the insulation pinched and on the verge of breaking down. Insulation resistance testign at 500V or even 1000V will normally find that.

I am not sure what he means by "checking the current and the earth" it's insulation resistance testing that will find this fault.

Keep calling them back until it is fixed. If they can't fix it tell them you employ a better electrician and send them the bill.
 

 

[NigelDent]

hi Dave,

thanks for post. The electrician came & isolated the whole circuit & tested for any faults in the line & couldn't find anything. I am assuming this was an insulation test. We now cannot run anything without a trip.

 

[Andy™]

 We now cannot run anything without a trip.

good. if the fault is always there and not intermittent, its much easier to find

 

[Murdoch]

Is it taking out the MCB and RCD every time?

 

[NozSpark]

IMHO unplug the washing machine for a few days and see how you go

 

[Evans Electric]

If everything is unplugged and it still trips , I'd be looking for a kitchen unit fixing screw into a flush cable somewhere.   Try testing to the screws .  Also plumber's pipe clip screws .

 

[Doc Hudson]

Has the RCD been tested to verify it is operating correctly within its specified characteristic?  If the work has been done correctly you should have an electrical certificate (full EIC or Minor) with the test readings he did prior to re-energising the circuit, this would have indicated any low insulation resistance on the fixed wiring.  Assuming this was done correctly and the fixed wiring is all electrically good, there may be a damaged appliance flex trapped under or behind, fridge, washing machine, dishwasher. Have any fitted or under counter appliances been physically slid out to check behind or just switched off from an above counter switch?

Did the MCB actually physically switch off, or do you mean the RCD removed power to the MCB?  RCD's are frequently supplying multiple MCB's. and the neutral and earths are common for all of these circuits. A neutral earth fault on any accessory connected to any of these circuits would trip the RCD when any one of the common MCB's are in use.  You may need to look at everything the RCD supplies.

Doc H.

 

[NigelDent]

Has the RCD been tested to verify it is operating correctly within its specified characteristic?  If the work has been done correctly you should have an electrical certificate (full EIC or Minor) with the test readings he did prior to re-energising the circuit, this would have indicated any low insulation resistance on the fixed wiring.  Assuming this was done correctly and the fixed wiring is all electrically good, there may be a damaged appliance flex trapped under or behind, fridge, washing machine, dishwasher. Have any fitted or under counter appliances been physically slid out to check behind or just switched off from an above counter switch?

Did the MCB actually physically switch off, or do you mean the RCD removed power to the MCB?  RCD's are frequently supplying multiple MCB's. and the neutral and earths are common for all of these circuits. A neutral earth fault on any accessory connected to any of these circuits would trip the RCD when any one of the common MCB's are in use.  You may need to look at everything the RCD supplies.

Doc H.

Hi Doc,

I  am now at the position where if I turn on the RCD that protects that circuit it trips the MCB within 2mins. The electrician is coming this morning as this circuit is isolated now as is tripping without any appliance connected to it.

 

[Sharpend]

This has all the hallmarks of a damaged cable, suspect as said kitchen cabinet fixings in line of electrical outlets, or more likely the fused spur has trapped the live conductor on the lug at the bottom of the back box when fitting back, one reason all unused lugs are hammered flat on spurs when I fit them. 

Look at the kitchen layout and visualise the cables within the wall, they should travel either horizontally or vertically through the centre line of the outlet. A quick method to establish any cable breaches by fixings within this line would be testing fixing for voltage when Mcb is ON. A safer approach would be with insulation testing followed by continuity test to locate. Any GOOD electrician would find this within a short time frame. 

 

[Doc Hudson]

Hi Doc,

I  am now at the position where if I turn on the RCD that protects that circuit it trips the MCB within 2mins. The electrician is coming this morning as this circuit is isolated now as is tripping without any appliance connected to it.

No, it is not isolated. All you will have done is to turn the power off by the MCB, but you still hall all of the neutral and earth wires physically connected back to the fuse box and RCD. 

Doc H.    

 

[ProDave]

Hi Doc,

I  am now at the position where if I turn on the RCD that protects that circuit it trips the MCB within 2mins. The electrician is coming this morning as this circuit is isolated now as is tripping without any appliance connected to it.

If it's tripping the mcb and not the rcd, it's more likely a L-N fault.  But with it tripping that often it should be easy to identify what's wrong (may be harder to get to it to fix it though)

Do let us know how you get on.
 

 

[Doc Hudson]

If it's tripping the mcb and not the rcd, it's more likely a L-N fault.  But with it tripping that often it should be easy to identify what's wrong (may be harder to get to it to fix it though)

Do let us know how you get on.
 

But the opening post says it trips the RCD? and supposedly the cable has all been tested as clear?

The electrician who carried out the work has been back to our house & isolated everything and checked the current and earth and the circuit is clear.

And it is also supposed to trip with nothing connected?

Yesterday (Saturday) was the worst day so far ! we started the morning with everything connected and the fuse blew 15 times from 10.30am to 1am, each time I removed an appliance from the circuit until the last time there was nothing on the circuit at all apart from a dining room plug socket switched in the on position but no plug plugged in (didn't spot it until this morning).

Either some miss-information or wrong terminology being used here I think. Something taking out a 32A MCB (15 times in two and half hours) would have given a few give-away flashes or bangs I would have thought?

Doc H. 

 

[ProDave]

I quite agree DOC we might be getting unclear information.

Did the "electrician" some today? did he find the fault?
 

 

[NigelDent]

So the electrician came this morning and the live cable from one plug socket to another plug socket had failed. Luckily we were able to drill down behind the worktop and run a new cable behind the sink and back up to the other socket to complete the circuit again. £15k of brand new kitchen, plastering and flooring it could have been a lot worse!!

Thanks for all your help

 

[ProDave]

Glad you got it sorted, and thanks for letting us know.
 

 

[Lurch]

£15kk kitchen and nothing down to protect worktops?

Hope their insurance premiums are up to date.

 

[NigelDent]

Would just like to say that my electrician has been amazing throughout. I didn't post on here because I  was disappointed with the electrician I was looking for a second opinion on what the problem could be.  The electrician rearranged his diary to fix my problem today and he has been available on the phone every time I called him. He has made good all of the mess and I wouldn't have known he had been there when I got back from my work meeting.

 

[Sharpend]

Well that just goes to confirm that there are some of us good guys still about.