Noob needs help

[thintin]

Hello, this is my first post so be gentle with me .

I have recently moved house and in my new house I have fitted a new kitchen. It includes a halogen hob and a split-level double electric oven.

Both were fitted by an electrician (it's a rented house so I needed a certified fellow for the insurance). This happened eight weeks ago. The oven was a graded second with full manufacturers warranty (Electrolux) and the hob was an ex-display model from IKEA (whirlpool)

Since this time I have had a problem with the mains tripping during the day when the appliances aren't in use (the oven has a digital clock/timer and the hob has LED's under the glass top to show when a hob is hot so both appliances are constantly live)

It is the RCD to the oven that is causing the trip as the main RCD will not reset without switching off the oven one first. After a few moments it all works fine again.

This has happened about four times so far.

How can I test the appliances for this kind of fault? Both the hob and the oven are connected to a single oven switch plate in the kitchen so I cant just leave one switched off to test the other when it happens.

I should also mention that the consumer unit was fitted new prior to our move and the wiring tested in the property.

Any advice gratefully appreciated.

Thanks.

 

[Qedelec]

Not a good idea to have the oven on the RCD side of the consumer unit, assuming you have a a split load CCu.
Get your electrician to move it to the other side of the board.
Electric rings can get 'leaky'.
Also you might have the appliance insulation tested.

 

[thintin]

"Not a good idea to have the oven on the RCD side of the consumer unit, assuming you have a a split load CCu. "

lets assume that I don't know what any of that means...

...the CU (is that the same as a CCu?)has a single row of about 6 or 8 circuit breakers, I called them RCD's but I'm not an electrician so they may have other names. At the end (RH) there is a bigger breaker which controls the whole lot.

I could assume it's an oven fault but if it isn't they'll charge me for the call out. If it's the hob I'm bugered cos I can't afford a replacement!

I just wondered if I could identify the fault before calling a sparky?

Are you saying the fault could be in the way it is all connected?

 

[JohnD]

The Consumer Unit (CU) is likely to be a split-load one. This means it will have a main Switch (probably marked 100Amp or 80Amp) which turns everything off; and and RCD (probably marked 30mA; Test regularly, then 100A or 80A or 63A) which provides Earth Leakage Protection to some of the circuits. These will usually be the Sockets and any electric shower, but not the lights.

Most often the cooker is not protected by the RCD.

You will also have Miniature Circuit Breakers (MCBS), one for each circuit. They act like fuses but look like switches. They are usually one-half or one-third the width of the Main Switch and the RCD.

They will usually be marked B6 (=6Amp for lights); B16 (16 Amps for immersion heaters); B32 (32 amps for sockets and some cookers); B40 (electric showers and big cookers).

However:
It is also possible to use an RCD as the main switch. This means that all circuits are protect against earth leakage. A disadvantage of this is that the light will go out due to, for example, a leaky steam iron, which can be inconvenient or dangerous if you are running downstairs; carrying a hot chip pan, or up a ladder.

Also:
It is common to have slight earth leakage on some appliances, particularly watery ones like immersion heaters and washine machines. this is usually very slight, and not enough to trip the RCD.
Cookers have large heating elements, and their background leakage can be enough to trip an RCD. This can happen with age or damage. As a cooker is not a particularly risky appliance (i.e. it is not portable, and will not be used out of doors or in the rain, like a lawnmower might) it is generally not considered necessary to put it on an RCD. This avoids the nuisance tripping that might otherwise occur.

If the Cooker Control Unit (big cooker switch) is one that includes a socket, it may be considered that someone will plug an extension lead to the lawnmower into it, and so it would be put on the RCD. Some people consider that this is one of the good reasons for not using CCUs with sockets.

 

[thintin]

I'll look more closely when I get home but I can confirm that the Cooker Control Unit has a socket on it (I dont currently use it just incase it was the cause of the trips) and the cooker control unit is definately wired to a trip switch.

With this being the case, can you guess at what is causing the fault, could it be this background earth leak building up to the trip switch's threshold?

If it is, what's the cheapest solution?

 

[JohnD]

I understand from what you say that the RCD is tripping, not the MCB. It is unusual to have earth leakage on an oven when the heateing element is not turned on. BTW have a look for any signs of water leakage near the switch or outlet.

1 - check if you have a split-load board or if all circuits are on an RCD.

2. If split load, the usual thing would be to move the cooker to the non-RCD side. It would be an advantage to replace the Cooker Control with a switch without a socket, in my opinion - though if your kitchen is short of sockets this may not be convenient. You will need an electrician to do these two things. (You may be able to persuade your landlord to pay on the grounds that it is not currently best practice, but this would be very arguable, and he may reasonably argue that it was done to standard by a qualified electrician, so it's your fault having a leaky cooker).

3. If not split load... will be harder. Let us know what make your consumer unit is; how many MCB positions it has, and if it has any blank spaces (and post a pic if you can).

It is possible to disconnect e.g. the Oven from the outlet plate to identify if it is the oven or the hob causing the problem. I do not know if you are competent to do that safely (not being rude).


If the CU was professionally fitted, and you have an installation Completion certificate by a qualified electrician with lots of test results, then it is unlikely to be the wiring at fault, much more likely to be the appliance. If the wiring was done by John Wayne or the landlord's granny, then you would be less confident.

 

[securespark]

If the cooker circuit has a socket outlet, it should be RCD-protected.

 

[JohnD]

I'm all in favour of sockets on RCDs, especially in a kitchen where water is present, but in many cases the CCU socket cannot "reasonably be expected to supply equipment used outdoors." We do not yet know if that is the case in thintin's property. No offence meant.

I greatly prefer the cooker switch not to have a socket on it. One of the other reasons is that people sometimes plug a kettle in and drape the flex over the hob where it gets burnt.

 

[flashbanger13]

Oops, wrong thread.

 

[thintin]

Thanks for all of your comments.

To answer the questions:-

"1 - check if you have a split-load board or if all circuits are on an RCD.

2. If split load, the usual thing would be to move the cooker to the non-RCD side. It would be an advantage to replace the Cooker Control with a switch without a socket, in my opinion - though if your kitchen is short of sockets this may not be convenient. You will need an electrician to do these two things. (You may be able to persuade your landlord to pay on the grounds that it is not currently best practice, but this would be very arguable, and he may reasonably argue that it was done to standard by a qualified electrician, so it's your fault having a leaky cooker).

3. If not split load... will be harder. Let us know what make your consumer unit is; how many MCB positions it has, and if it has any blank spaces (and post a pic if you can). "

I will include a photo of the board but all the switches look the same appart from the main one?

Now, where do I post pics?

Replacing the Cooker Control Panel with a socketless one is no problem, I feel confident to do that and there is a double socket nearby so no shortage of usable sockets.

So, just to confirm (can you tell I was a teacher)

The trip is being triggered by a build up of earth leak?

If the oven and hob weren't connected to an RCD (or whatever the trip switch thing is called) there probably wouldn't be a problem?

Moving the oven/hob to a non RCD supply would solve the problem but only if the Cooker Control Panel has no socket?

Does this cover it?

 

[JohnD]

I will include a photo of the board but all the switches look the same appart from the main one?

Now, where do I post pics?
//www.diynot.com/forums/viewtopic.php?t=8463 and photobucket

Replacing the Cooker Control Panel with a socketless one is no problem, I feel confident to do that and there is a double socket nearby so no shortage of usable sockets.

There are regulations controlling electrical work in kitchens and bathrooms within England and Wales.

So, just to confirm (can you tell I was a teacher)

The trip is being triggered by a build up of earth leak?
Probably. It doesn't exactly build up, like a bucket filling. You get several small leaks, and possibly a larger one from a defective appliance, each has a small current flow, and the flows reach an amount that is detected to exceed the trip current. Alternatively there can be a single major fault that would be capable of causing a severe shock, which will immediately trip the RCD all on its own.

If the oven and hob weren't connected to an RCD (or whatever the trip switch thing is called) there probably wouldn't be a problem?
Depends how much of a leak there is. There might be a significant flow due to a defect. Or it might be very slight and not worth worrying about. You would need to have it tested to find out. There is an assumption that cookers will leak a bit.

Moving the oven/hob to a non RCD supply would solve the problem
Well, it would certainly prevent the RCD tripping, which was the presenting problem. Without a test you will not know if the leakage is worth worrying about. I do not know how you would test for it (I have access to a PAT tester i would use, or a clamp meter might do it). Most electricians should be able to test. Somone else on here might have an idea. Otherwise you are no worse off than the other 95% of the population who have a cooker with no RCD on it.

but only if the Cooker Control Panel has no socket?
I don't think you are obliged to have a CCU socket RCD protected. The requirement is to protect sockets that could reasonably be expected to be used for equipment outside the equipotential zone (e.g. a lawn mower in the garden) and in most cases people would use the nearest socket to the back door, not the cooker socket. But it is preferable to have all sockets RCD protected to reduce the chance of shock.

Does this cover it?

Someone cleverer or better informed than me will probably be along in a minute to correct my errors and omissions.

 

[thintin]

I've sent the pics to the forum administrators to post for me but the details are:-

Main switch is 'RCCB 80A 30mA'

Shower, Cooker, Sockets, Sockets are all 'D247 B32 400v IEC898'

Shed Sockets 'B20 then as above'

Heating, Lights 'B16 then as above'

no other empty slots.

There is no manufacturer name, just a logo. It looks like a red, right facing triangle inside a black oval with a red line extending from the right hand tip of the triangle.

Does this help?

 

[JohnD]

Ah.

Sounds like you have an RCD as your main switch.

So all your circuits are controlled by the RCD (this will mean that your lights go out if it trips?) This is not considered best practice, as it will be inconvenient making a repair in the dark, and can be dangerous if you are running downstairs, or carrying a hot chip-pan, or up a ladder.

In which case you have no non-RCD ways available.

I feel an electrician's visit coming on to make a change to the installation.

I think I have seen the logo you mention, I have an idea it is the CGD brand. Is it like this?

In your position I would probably disconnect the oven and see if the hob runs OK.

 

[thintin]

Thats the feller! Add another half a dozen switches and thats my CU.

I ruled out disconnecting either the oven or hob because the trip only happens about every two weeks so it would be inconvenient to loose the use of either appliance for that long.

The house I'm in is rented and the CU was fitted just before I moved in so the landlord probably asked for the cheapest solution available!

I need to get an electrician in to connect my shower to the CU so maybe I'll be asking them to test the oven and hob whilst they're here?

Thanks for your help everyone. Please feel free to post any more solutions/thoughts about my problem.

 

[JohnD]

...I need to get an electrician in to connect my shower to the CU so maybe I'll be asking them to test the oven and hob whilst they're here...?

tell them you'll want an earth leakage test on the cooking appliances, otherwise they may not bring the appropriate tester and leads.

Good luck!