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Author: Subject: Domestic Electrics Issue - Advice Please
John P

posted on 25/9/21 at 02:39 PM Reply With Quote
Domestic Electrics Issue - Advice Please

Hi,

We have a 1960's bungalow which has obviously been rewired at some point although it does only have a single ring main which I appreciate isn't ideal but hasn't actually caused any issues.

Last month, when my wife had the oven on, the whole house suddenly lost power. (The only other items being used would have been things like the fridge and freezer).

I checked the consumer unit expecting the MCB on the cooker circuit would have tripped but it hadn't. Also the RCD switch was still in the correct position so initially I thought it may be a power cut but when I checked with the neighbours their supply was OK.

I turned the RCD off and then on again and everything went back to normal.

This afternoon, again whilst the oven was on, the same thing happened but I can't understand why the whole house should effectively be tripped out without any of the MCBs or any visual indication on the RCD.

The only thing I did wonder is if the oven element could be starting to fail. The reason for this is that although only 7-years old I have already had to replace the main oven element twice but on those occasions it either blew very obviously with a visible hole in the element or the cooker MCB tripped.

Any advice,
John.

PS. Although not a qualified electrician, before I retired I did work as an electromechanical engineer and when it was still allowed also rewired a number of properties so I do have some experience even though I know I can't officially do that much myself.

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Sanzomat

posted on 25/9/21 at 03:28 PM Reply With Quote
That is an odd one. As you say, if there is a RCD in the circuit then pretty much anything wrong would cause it to trip out, the only exception being a simple over-current on the circuit without any other fault (e.g. when an element fails giving a current surge but no short to earth or neutral). So, if the power has been cut off to the whole house then it seems to me that the RCD did trip but maybe the lever got stuck in the on position even though the contactor itself had tripped? That would also explain why turning the RCD off and on again brought the power back on.

So, my interpretation (for what its worth) is that the RCD is functioning but has a sticky lever and there is a fault somewhere that is intermittently causing it to trip out. All sorts of wiring faults could do this but an oven element on its way out can do this - I've had it happen too - kind of goes but then causes an arc that "welds" itself back together for a few days before it finally goes altogether.

Good luck diagnosing the fault - a methodical approach should get you there.

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BenB

posted on 25/9/21 at 03:29 PM Reply With Quote
How about this as a possibility- the RCD is knackered and partially tripping but it's only become obvious now because the element in the oven is earthing (I also knackered). When elements go it seems to be 50/50% whether they make a dead short and blow the MCB or leak to earth and trip the RCD.
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BenB

posted on 25/9/21 at 03:54 PM Reply With Quote
I was too slow!!!
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David Jenkins

posted on 25/9/21 at 04:56 PM Reply With Quote
Our RCD trips whenever a lamp blows in the oven...





The older I get, the better I was...

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gremlin1234

posted on 25/9/21 at 08:48 PM Reply With Quote
change the RCD for an equivalent new one, monitor for a week then bin the old one.
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cliftyhanger

posted on 26/9/21 at 09:35 AM Reply With Quote
quote:
Originally posted by gremlin1234
change the RCD for an equivalent new one, monitor for a week then bin the old one.


Yes, this is sensible unless you wish to pay an electrician to come out, test the RCD (my meter will slowly ramp up the earth leakage and tell me teh actual trip current, likewise it can tell me how fast it trips)

But a new RCD will be cheaper and likely fix the issue.

The problem is that RCDs are supposed to be tested every 6 months, it used to be more regular but few people bother. But it is essential to stop them sticking.

As to the cause, element is best bet.

But next week I am off to swap an RCD for a customer as their year old Bosch oven (extended warranty too) keeps tripping one RCD (2 RCDs in their board) and despite me testing the RCD and it being spot on, Bosch engineers can find no fault with the oven after 5 callouts. And suggested the RCD must be faulty.
I have explained in writing that I do not believe the RCD is faulty, and that I am changing it at her request and I expect to be paid even if the oven still trips.
Still, she will have a certificate to show it has been changed and all working fine.....

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britishtrident

posted on 1/10/21 at 11:59 AM Reply With Quote
Oven element we have had this a couple of times.





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― From BBC TV/Amazon's Ripper Street.
[/I]

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BenB

posted on 1/10/21 at 04:53 PM Reply With Quote
The one which got me was when we had a washer drier. The heater element blew on that a couple of times. The first time was nice and easy- you could put it on a dry cycle and the clothes would come out wet and cold. Second time was a head scratcher just because the RCD kept on tripping on wash cycles (which we do more of). Transpires when you start a wash cycle it would "blip" the air heater element (got knows why) so even in cycles for which the air heater was not used it would still blow the RCD as it had failed to earth.
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coyoteboy

posted on 1/10/21 at 11:44 PM Reply With Quote
quote:

The problem is that RCDs are supposed to be tested every 6 months, it used to be more regular but few people bother. But it is essential to stop them sticking



Are they? Christ, no chance in hell I'm resetting all my clocks every 6 months 🤣





Report your local potholes, it actually works!

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gremlin1234

posted on 2/10/21 at 08:42 AM Reply With Quote
quote:
Originally posted by coyoteboy
quote:

The problem is that RCDs are supposed to be tested every 6 months, it used to be more regular but few people bother. But it is essential to stop them sticking



Are they? Christ, no chance in hell I'm resetting all my clocks every 6 months 🤣

thats simple, just test it when the clocks go forward/back for summer time /gmt

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indykid

posted on 2/10/21 at 08:46 AM Reply With Quote
quote:
Originally posted by gremlin1234
quote:
Originally posted by coyoteboy
quote:

The problem is that RCDs are supposed to be tested every 6 months, it used to be more regular but few people bother. But it is essential to stop them sticking



Are they? Christ, no chance in hell I'm resetting all my clocks every 6 months 🤣

thats simple, just test it when the clocks go forward/back for summer time /gmt

You have to move them an hour every 5 and 7 months anyway.

Just test it at midnight





me? ambivalent? well, yes and no

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cliftyhanger

posted on 2/10/21 at 10:06 AM Reply With Quote
quote:
Originally posted by indykid
quote:
Originally posted by gremlin1234
quote:
Originally posted by coyoteboy
quote:

The problem is that RCDs are supposed to be tested every 6 months, it used to be more regular but few people bother. But it is essential to stop them sticking



Are they? Christ, no chance in hell I'm resetting all my clocks every 6 months 🤣

thats simple, just test it when the clocks go forward/back for summer time /gmt

You have to move them an hour every 5 and 7 months anyway.

Just test it at midnight


Which is exactly why the guidance changed from 3 monthly to 6 monthly.
At least you don't have to mess with the car clock...

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