Electrical Mystery

[MartinAdvice]

Hi

I have a problem with small electrical installation:

My neighbor ask me if I can check why her OVEN is taking her MCB OFF. I find out that her OVEN (5.1kW) is connected to kitchen ring with all other stuff like Fridge, Washing Machine etc.and is protected by 32A MCB on 2,5mm Twin and earth cable. Not the right thing to do, I have explained that she needs designated supply to her oven with the right sizes of cable and dedicated MCB. 

I have replace an old spare 16A MCB with New 32A MCB, I run 10m of 6mm twin and earth cable from the MCB to brand new Oven Switch. Now is the mysterious part: 

The moment I put ANY LOAD on this circuit it take RCD OFF (RCD 63A, delta N 0,03A, TSB brand), on the first instance I was thinking that a OVEN itself is faulty but I have connect my site lamp and even a small charger to it and takes RCD right away. My next check was OVEN SWITCH, I test it and is OK, I even replace it with 2 different switches and still once the I SWITCH it ON the RCD goes OFF. Following that I have replaced my new 32A MCB with another one, still same fault. Ten I was thinking that it must to be a cable so I test it. Continuity test OK, Insulation Test OK (All test with FLUKE 1664 FC Multifuncion Tester). Everything else is fine, all other circuits works fine. It is ONLY the new bit I install it which takes RCD off the second I put the LOAD on it. No other MCB's goes OFF, only RCD. I have found that there is a small leakage on one of the circuits but it doesn't affect whole installation. I'm out of ideas. 

Anyone knows what could be a problem? 

Many Thanks

Martin A

 

[Joseph Howarth]

Is it a Dual RCD board?

You could have the neutral of the oven circuit on the wrong neutral bar

 

[Sharpend]

Checked neutrals at cu?

 

[ProDave]

The RCD trip problem is almost certainly wrong neutral bar as Mr Duck suggests

I will guess this is a double oven, so it will only draw that sort of load when both ovens are in use. A single oven typically takes a little over 2KW.  It would also not surprise me to find your new circuit also trips as there may be a fault in the oven itself. Although feeding it from a ring final is not perfect, I would not expect it to trip that unless you have lots of other things like washing machines, dishwashers etc all on at the same time.
 

 

[Blue Duck]

Where is Mr Duck?

I vote neutral in the wrong side of the arseedee there is also the consideration that the cooker maybe fubar'd ???

Just not doing any meaningful work this close to Christmas.

:bucking-reindeer-smiley-emotico

 

[Sharpend]

It's alright Daves getting new glasses for Xmas. 

 

[ProDave]

It's alright Daves getting new glasses for Xmas.

this sort? yes please :Y

 

 

[Sharpend]

this sort? yes please :Y

 

I was kinda thinking that perhaps you've had too many of that sort already!! 

 

[Lurch]

Anyone knows what could be a problem? 

Clueless person doing the work?

The "randomly rewire things until it sort of works" method is not how you are meant to do it. I would advise your friend that they need an electrician to do the work.

 

[Rob.]

So the only test you did was after installing it, after repeatedly trying to energize the circuit and replacing several parts....

Yeeee haaawww 

 

[kerching]

:shakehead

 

[Sharpend]

I thought he mentioned a fluke 1664fc ??

 

[Murdoch]

He did......oh and OP, this is notifiable under part P too - the icing on the cake I'm thinking!

 

[ProDave]

I do hope Martin A comes back to tell us if it was just the neutral in the wrong bar, and whether the oven now works or not.

P.S not all of the UK is covered by part P :innocent
 

 

[Murdoch]

I do hope Martin A comes back to tell us if it was just the neutral in the wrong bar, and whether the oven now works or not.

P.S not all of the UK is covered by part P :innocent
 

well maybe not but the OP is in London - so it does apply and in a recent article it would seem Select is pushing for this in Scotland!

 

[MartinAdvice]

Hi Guys

Many thanks for you help, as the matter of fact I had fed Neutral from right hand side bar of DB (new MCB is on right side), hopefully that will work. I will let you know ASAP.

In the mean time I wish you all a Happy New Year!!! 

 

[M107]

Clueless person doing the work?

The "randomly rewire things until it sort of works" method is not how you are meant to do it. I would advise your friend that they need an electrician to do the work.

:slap  

I've just got in from sorting out an oven for a customer who had a new cooker to go on existing circuit...... "it tripped rcd now he's changed the wiring on the back of cooker & not put the switches back to the wall, it wont even turn on"..........the clueless diyer.......sorry handyman,  was still there with the customer to see what the actual issue was as he thought it was the old wiring at fault. 

1. at the switch trying to push everything into a 25mm back box, crushed neutral onto cpc tag of backbox (he did find this himself so fixed it ............with tape, but RCD still tripped.
   
2. dropped one of the oven terminal screws (1 of three neutral terminals) in the back of the housing, couldn't reach it as no torx drivers to undo the rear casing so had used a gutter bolt he found in the van.
   
3. the dropped screw had fallen behind the thermal insulation onto the light & was sat across the terminals & chassis ..... RCD didn't like it.
   
4. had also lost one of the link bars  between the line terminals (hence it didn't work) in the housing along with the screw.
   

What did I do ....

The handyman was given a deeper back box to chop in.

I retrieved the screws/link bar & binned the gutter bolt, gave them to the handyman to refit

Tested circuit .

watched handy man connect the cooker.

switched on.

Took the £50 off the handyman he was charging & told him to give up electrics, told customer to use competent trades persons in the future & a cooker connection should be no more than £25 / £30..........job done

 

[Lurch]

a cooker connection should be no more than £25 / £30.

I'm subbing out all my cooker connections to you then.

 

[Murdoch]

a cooker connection should be no more than £25 / £30..........job done

Excellent - I assume that includes all the parts required and as I'm not too far away I sub you all my cooker installs ...... then sit back and take the profit

 

[Sharpend]

Well if it includes travel, I might have a few for you too!!