Faulty RCD?

[nigel_jewell]

Hi all,

Recently our RCD has been tripping when we have been using the cooker grill. This has become more and more frequent, to a point where it is guaranteed that using the grill will trip the RCD every time, but at a random point in time.

My initial thought was that the grill element had reached the end of its life, so I bought a new one. Upon fitting it I found that the RCD would trip even quicker than with the old element (now 10 seconds). Suspecting that the new element may also be faulty, I asked the supplier to check it and send me another. The second new grill element also trips the RCD very quickly (also around 10 seconds). Unless I am very unlucky I don't think that two new grill elements will be faulty - unless the supplier has a dodgy batch.

My second suspicion was that the cooker may have a fault somewhere, so I have taken it apart, bypassed switches, limiters etc until I reached a bare bones connection where the grill element was essentially connected directly to the wall mounted cooker switch which is in turn connected to the cooker MCB and the RCD. Again, the RCD trips very quickly (about 10 seconds).

This has led me to suspect that the RCD may be at fault. So, I've opened our consumer unit and disconnected all other MCBs apart from the cooker (of course), and tried it again. Still the RCD trips, highlighting that the RCD is only being tripped by the leakage coming from the cooker/grill element.

So, I am getting more and more convinced that the RCD may be at fault. It is a Wylex WSES 80/2 30mA that is probably around 15 years old (or more).

Does this sound plausible, or is there a chance that I have missed something else? Do RCDs tend to fail in this way? Could it still be the grill element?

I've had a dig around the 'net and I can't find a direct replacement part (I am assuming that a new model will be required - Wylex WRS?) and therefore I suspect that the consumer unit will also need replacing. I don't want to get this done and still find that there is something else that it as fault.

Any ideas/help/advice appreciated. Please!

Regards,
Nige.

 

[RF Lighting]

It's highly unlikely that the RCD is at fault.

It suspect the cooker it self, but the fixied wiring may also be at fault.

Have you treid disconnecting the cooker from the cooker outlet plate?

Does the RCD still trip?

Does the RCD trip if the cooker is connected, and all its controls are off?

Does the RCD trip if you turn say the oven on, but not the grill?

Is there a socket outlet on the CCU? if so is there anything plugged into it?

Is the whole house protected by a single RCD, or do you have a split load setup?

 

[nigel_jewell]

Hi,

Thanks for your reply.

I haven't tried connecting the cooker without the outlet. Maybe that is the next thing to try.

The RCD does not trip when the cooker is connected and all of the control are off. Similarly, it does not trip when the oven is on and not the grill. It ONLY trips when the grill is turned on. With a new element this always takes around 10 seconds. With an old element this takes a random amount of time.

There is a socket outlet on the cooker outlet. There is nothing connected to that.

Regards,
Nige.

 

[bengasman]

Sounds like the grill and not the rcd. Is it possible internal wiring has come loose? Cooking residue somehow entered into an electrical connection? Dirt or damp in controls? Damaged or brittle insulation?

 

[securespark]

It's highly unlikely that the RCD is at fault.

Hate to disagree, Rob, but I find these often, where the RCD trips on the 1/2 x test & you do a ramp on it and it comes back with 15/6mA.

Also, elements can be damp which can trip RCD's. Could it be that?

 

[nigel_jewell]

Hi all,

I have tried "cooking" the element before use, this hasn't helped at all, and all of the cooker cabling and connections are in good condition.

Thanks for all of your replies - very helpful. I think that I've come to the conclusion that I'll get someone out to test the RCD and the element. I think I've reached the end of the line with what I can do.

Can anyone recommend a good electrician in the Bristol area?

Thanks,
Nige.

PS. Appologies if you've seen this subject on more than one forum. I often find the responses to messages on forums to be a little bit "random", so I thought that I would give myself the best possible chance of getting a decent reply .

 

[Steve3948]

If you speak to Wylex they will tell you that when the units were manufactured they never had the technology for accuracy as they have today, so a ramp test can show that this device could trip with a very low leakage.
Therefore it could be a bit of both.

Did you remove all the neutrals in your fuseboard, or did you just isolate the mcb's.
If all your neutrals were left in place in could be accumulative leakage combined with a sensitive rcd.

Replacing the rcd for a modern device could clear the problem, however the installation should be checked for further leakage if all the neutrals were left connected.

You could also have a fault in or around the regulator for the element.
Some elements are also secured with a bracket very near to the terminals and I have seen where the bracket or the cover plate is near to touching a element terminal and that was the problem.

 

[derekwalters]

I have exactly the same issue - did you get a resolution on yours?