New RCD necessary?

[katy1980]

Hi all. 

I hope I have come to the right place for advice on an issue I'm a little unsure of:

When we turn cooker on it works for about 30 seconds then electrics blow (cooker is pretty new - less than a year old Bosch double oven). It's as if when the heat starts to kick in it trips (but turing RCD switch back on after tripping - oven always works fine then and doesn't trip again). Electrician came to find fault and claims we need new RCD circuit board as our existing is too small for the house (its a single switch one so he is getting a double). My concern is that we only use one bedroom and landing plus main living room and kitchen - so would existing really not be able to handle that? (The house is quite big; 4 bedrooms, 3 reception rooms, a huge landing that I work on, kitchen and utility room so it is pretty big - but 3 rooms are guest rooms/not used for electricity - apart from lights - and one reception room never has anything plugged in either).

I guess I was a little unsure about how much we really needed a new board when I remember electrician saying he was struggling to find a circuit breaker for our board (the day before he came to work on the fault properly - which was when he said we need a new RCD and the fault cannot be fixed). In my mind I think we would just need a stronger breaker (or whatever it is!) for the board for the cooker switch - but I know NOTHING - and realise it's probably not so black and white so forgive my naivety!)

Anyway, £380 for a bigger RCD board to replace the existing RCD board (which is an OK quote from what I've been told - not great, but not bad either, I live in Huddersfield, Holme Valley area) and he's fitting it tomorrow - just before we go on holiday early hours Tues night/Wed morning so I'm stressed if need to do last minute work (I have an online business) or cleaning clothes etc. Paranoid it will all go wrong and not be able to shower before I go to the airport (catosraphising silly worrier? That's me!)

I'm wandering if this solution (new RCD) sounds correct? I don't get how we have had cookers etc working fine for nearly two years since we moved in - and all of a sudden our circuit board can't take it. We really need to get it done tomorrow because my aunt is looking after house and I can't leave her with a cooker that trips as going down to garage and turning the alarm off/on and flicking electrics switch is like asking her to run a marathon (she's of "mature" age and things like that would be a big deal for her).

Thanks and sorry to ask but it's playing on my mind and stressing me out before my jollies!

 

[katy1980]

P.S. I think we probably do need a bigger RCD due to house size - but my main concern is if this even fixes the cooker issue. I don't want an electrician here half a day doing a job that's not essential/relevant to the issue when I could have been getting work done before I go away

 

[steptoe]

Changing your consumer unit will not fix the fault. 

 

[katy1980]

Thanks for your reply.

Can you please elaborate? If that's the case I want to cancel the electrician as I'm not paying him for work I've effectively been tricked into needing (yes, I may need ideally a newer unit - but I'm not forking out for one if he's wrongly informing me/tricking me into unecessary work. I'd go elsewhere instead)

I could do with a reason so I can justify what I say to him?

Thanks

 

[steptoe]

Can you post a picture of your existing consumer unit and tell us which switch is actually tripping off,

Putting it simply,if you have a leaking tap, changing your stop cock isn't going to fix it. 

 

[katy1980]

Please find picture attached. oven has it's own connection

Thank you

 

[katy1980]

The cooker is causing the board to trip (right hand switch) - BUT the right hand switch doesn't trip at all - it's the main switch on the right that trips so perhaps it's true the system cannot handle all the power to the house...?

Sorry - I mean it's the main switch on the left that trips (the cooker switch didn't trip - but it's the cooker that causes the board to trip!)

 

[Doc Hudson]

A few problems I see here are;  A) From the information given it is impossible to tell if the electrician has done sufficient tests to verify if the RCD is working correctly or not and if you have a fault that still needs identifying. B) The RCD may be oversensitive and may just need replacing rather than the whole board.  C) It is not good practice to have a single RCD protecting the whole board which is probably why the electrician is saying it needs replacing.  D) Some oven manufactures specifically state that their appliances should not be connected via an RCD due to some natural leakage during operation.  E)  The RCD tripping is nothing to do with too much power going through the board, RCDs detect very tiny amounts of leaking electricity making a path to earth. they are there to prevent fatal electric shock, You may well have an issue with a faulty appliance or circuit cable that the RCD is detecting. F) You have left it rather late to seek a second opinion if it is due for replacement tomorrow!  You mention that you run your own business, how happy are you with customers agreeing to work then canceling at the last minute. (however legally you are probably within your right to cancel if the contractor hasn't given appropriate cooling off period as per the doorstep selling regulations.). I would suggest you get a second opinion with someone who can come and test the RCD fully and the associated circuits.  As Steptoe points out if there is a genuine fault on a circuit, or an excess of natural leakage through the single RCD then replacing the consumer unit will not fix anything.

Doc H.

 

[katy1980]

The issue started only last week. He came just a few days ago to work on finding the fault and that's when he said we need new RCD. Literally 2 days later (now) I've thought about it and wondered if it's necesary - hence not left it last minute as such - and just started to question the necessity. Trying to get someone - but very short notice so its unlikely.

As you say it's worth changing the board anyway so I guess we may aswell go with it. Thanks for all your help and the useful information. Much appreciated :Salute

 

[Sharpend]

So the left hand main switch is an RCD the others are MCB's, both devices are protective devices which operate under differing fault conditions. 

Given that the RCD trips I would suggest that the electrician should be testing the cable from the board to the cooker then providing this is satisfactory (and from what you describe it is) he should be testing the cooker. I suspect that this is an element of thermostat breaking down within the cooker. If the appliance is as new as you indicate I'd be tempted to call bosch and ask for an engineer to attend, he will know and test the appliance thoroughly. 

Ideally you need a better electrician. 

 

[Doc Hudson]

There are specified tripping times and current that the RCD must operate within for it to be compliant with BS7671 wiring regs and to offer safe disconnection of power in the event of a fault. A competent electrician can verify this comfortably within in 10 or 15 minutes using a suitable RCD tester. If the RCD is working correctly a new board with another correctly working RCD will most likely give the same symptoms. Have you still got the instructions for your oven, what do they say about electrical connections.

Doc H. 

 

[katy1980]

I'll dig out instructions and have a look. Thanks again all. What did we do before the internet?!

 

[Doc Hudson]

. What did we do before the internet?!

I think it was called the telephone and letters, or visits to a shop or trade counter.

Doc H.

 

[katy1980]

Letter? Never heard of it....

 

[ProDave]

If the RCD and cable tests okay, then testing the oven (is is just a double oven or an oven and hob?) is not quite so easy.

A lot of ovens won't turn on the elements until you have set the time, so testing them for leakage is not the whole story as the elements will not be on. you might need to take the oven out of it's housing take the covers of, and test the elements individually.

Like was said a few posts ago, you need a better electrician.

Did you see him actually doing any tests with a complicated looking meter at the consumer unit?

 

[katy1980]

Hi

As board is in garage I didn't really see much of what he was doing (I don't like to hover around tradesmen as I imagine that's a bit annoying!) I have messaged him and he said he did tests and it couldn't handle a high output of power - so this makes me think it's ok to add new RCD? However, I asked if he checked the element and he said he didn't "because it tripped when I was testing zs, the cooker was isolated" (hope that makes more sense to you than it does to me!) Does that help explain everything and I should just leave him to replace RCD as planned? I just don't want to be replacing it just before I go on holiday if that's not the cause of the issue.

My only concern is that I've read things on other forums (that I don't quite understand so probably can't explain very well!) - but I've read that it can trip as it hits a certain temp due to a leak/fault in the oven wiring (or element). So surely he should look at this first? (ours oven does work for a minute or two before tripping - but when I turn RCD switch back on it doesn't trip again which confuses me even more). Or does the fact he tested when cooker was isolated mean I don't need to be concerned about that?

I'm left wondering that - yes, we do need to update the RCD - but that won't fix the cooker issue? I guess I can't get my head around why it would work fine for nearly a year but then the RCD suddently can't handle everything (so then I'm back to thinking the RCD is fine - there's a system fault!) In a nutsheel; I don't want to be paying out nearly £400 just before I go on holiday if it's not necessary! Also, as I'm going away,I'm fretting for my aunt looking after the house, she doesn't have great health so I want her to be able to relax with no little niggles to stress her out.

 

[katy1980]

Oops, sorry - yes it's a double oven. Main oven at the bottom and grill at the top which also works as an oven. The RCD main switch trips regardless of which I use (but the oven's MCB switch doesn't trip - it's the main switch that trips indicating that perhaps it is just the system overloaded/hence new RCB possibly being the correct plan all along and I'm worrying for nothing?)

Whatever the outcome I'll post on here as it may come in usefull for anyone else who has the same issue.

 

[steptoe]

As said previously, the RCD has nothing to do with too much power being used, but rather with a fault somewhere.

Some test meters will cause some RCDs to trip while testing Zs, so this is not proof of a defective RCD,

Also, it could be a different circuit causing most of the leakage(fault) and the cooker is merely the tipping point.

Much more comprehensive testing is required,

In short, a better electrician required, it just sounds like a massive upsell to me,

How long has this 'electrician' been in trade for,? 

 

[ProDave]

Hi

As board is in garage I didn't really see much of what he was doing (I don't like to hover around tradesmen as I imagine that's a bit annoying!) I have messaged him and he said he did tests and it couldn't handle a high output of power - so this makes me think it's ok to add new RCD? However, I asked if he checked the element and he said he didn't "because it tripped when I was testing zs, the cooker was isolated" (hope that makes more sense to you than it does to me!) Does that help explain everything and I should just leave him to replace RCD as planned? I just don't want to be replacing it just before I go on holiday if that's not the cause of the issue.

That smells of either BS or incompetence.

That RCD ia rated at 100A so it can take all the power the house can use.

The issue appears he has neither tested the RCD for correct operation,. or tested any of the circuits to see which one(s) has the leakage.

There is an argument for changing the board as he suggests but that is ONLY so that only part of the house trips if there is a fault. Changing the board will NOT stop it tripping, unless of course the reason for tripping is the present RCD is over sensitive. and if that is the case you only need to replace the defective RCD, not the whole board.

 

[Rob_the_rich]

Katy, is it really necessary for your Aunt to have a working oven while you are on holiday? The hob will be working, the kettle and the microwave(?) too.

How many sunday roasts is she planning?

Just seems to be less stressful all round if she doesn't use it. You can then get it looked at by someone at your leisure.

Edit; oops, just saw your post about it being a double oven and grill. Your decision though still. I agree with the above, it would have taken the "electrician" less than a minute to plug in a test instrument into any socket and test the RCD. You would have then known whether the RCD would need replacing. The fact that he didn't do this means he is trying it on, and I would not have him back.