cooker trips CDC

[Mick1308]

After working ok for many years my cooker started to trip the CDC, not immediately but after a minute or so of being turned on.
Not necessarily the heating elements but just the interior light.
Thinking the fault was with the cooker I replaced it.
The new cooker does exactly the same.
I have replaced the CDC but the problem persists.
The wiring from the cooker goes to a terminal block which also has the hob connected.
The hob works fine, the problem occurs regardless as to whether the hob is on or off.
It seems unlikely that both the new and the old cooker had the same problem.
I could start testing the new cooker for faults but as the problem occurs only after several minutes I don't think that will work.
I am baffled, any ideas folks?

 

[poni]

whats a CDC?

 

[ProDave]

This is a lesson why fault finding by swapping random parts (in this case the cooker which I assume means oven) can be more expensive that just getting an electrician to do some proper testing to determine exactly what is wrong.

 

[Mick1308]

whats a CDC?

differential circuit breaker

 

[Mick1308]

This is a lesson why fault finding by swapping random parts (in this case the cooker which I assume means oven) can be more expensive that just getting an electrician to do some proper testing to determine exactly what is wrong.

A new CDC748M cost £18, if you will come and test it for less you're hired.

 

[Mick1308]

A new CDC748M cost £18, if you will come and test it for less you're hired.

the cooker was quite old and I already had the replacement ready to go. The problem just forced me to install it.

 

[newfutile]

is that Hagar (RCD) Residual Current Device ? where do you get them for £18 ? this will most likely cover many circuits and if so it don’t mean the cooker circuit is faulty , though it could be, tripping on any load suggest neutral to earth or neutral on wrong bar, can you post a pic of the Consumer Unit ?

 

[ProDave]

A new CDC748M cost £18, if you will come and test it for less you're hired.

I meant you replaced the oven and that turned out not to be the fault.

 

[Andy™]

my guess is the old oven had a failed element tripping RCD, the new one has been standing around for a while and the elements are damp so also tripping RCD. they have then jumped in with replacing the RCD when there nothing wrong with it, its just the new oven is also faulty. if it is dampness, then it can be fixed but im not saying how to do that, although you could probably figure out one of the few ways to get the oven on and hot enough to dry out without tripping an RCD...

 

[Mick1308]

is that Hagar (RCD) Residual Current Device ? where do you get them for £18 ? this will most likely cover many circuits and if so it don’t mean the cooker circuit is faulty , though it could be, tripping on any load suggest neutral to earth or neutral on wrong bar, can you post a pic of the Consumer Unit ?

The problem only happens when the cooker is switched on, the hob is on the same circuit and functions ok. The strange thing is that all I have to do is switch the oven on which only activates the light, none of the heating elements. It takes 30/40 seconds before the rcd trips.

 

[Mick1308]

my guess is the old oven had a failed element tripping RCD, the new one has been standing around for a while and the elements are damp so also tripping RCD. they have then jumped in with replacing the RCD when there nothing wrong with it, its just the new oven is also faulty. if it is dampness, then it can be fixed but im not saying how to do that, although you could probably figure out one of the few ways to get the oven on and hot enough to dry out without tripping an RCD...

Thanks for the suggestion but I don't think a failed element caused the original problem because the rcd tripped without any of the heating elements being on, just the light. If it is a damp problem then maybe it will fix itself after being in the house for a little while.

 

[Murdoch]

Reversed n- e on the new cooker?

 

[ProDave]

Post picture of where new oven is connected, presumably to a cooker outlet plate?

What IR tests have you done on any / all circuits?

 

[michael8554]

What make and model of oven was the old one ?

Most likely the oven element is permanently attached to a circuit board that is powered up when you switch the oven on.

Which incorporates the on/off, temp, and timer functions, rather than a simple switch.

So if the element is starting to fail, it may short out that board and trip your RCD.

 

[Mick1308]

Reversed n- e on the new cooker?

possible, I guess I will just have to open it up and start testing.

 

[Mick1308]

Post picture of where new oven is connected, presumably to a cooker outlet plate?

What IR tests have you done on any / all circuits?

 

[binky]

Thanks for the suggestion but I don't think a failed element caused the original problem because the rcd tripped without any of the heating elements being on, just the light. If it is a damp problem then maybe it will fix itself after being in the house for a little while.

Unless the light is on its own switch, then when you turn oven on it will almost certainly be energising a heating element. Your new oven may also trip the RCD purely down to damp in the oven insulation, it's a common problem with ovens that have been hanging around for ages but not in use. The fun bit is trying to dry it out.

 

[Mick1308]

The cooker connects to a terminal black together with the hob. The feed then disappears into the wall and emerges at the consumer unit. Didn't want to believe both cookers could have a similar problem but will have to concede defeat and start testing the new cooker.

 

[Mick1308]

Unless the light is on its own switch, then when you turn oven on it will almost certainly be energising a heating element. Your new oven may also trip the RCD purely down to damp in the oven insulation, it's a common problem with ovens that have been hanging around for ages but not in use. The fun bit is trying to dry it out.

ok thanks I will set about dehumidifying it.

 

[poni]

The problem only happens when the cooker is switched on, the hob is on the same circuit and functions ok. The strange thing is that all I have to do is switch the oven on which only activates the light, none of the heating elements. It takes 30/40 seconds before the rcd trips.

this does not look like a UK set-up, all the blacks and blues ( I never knew that is what a RCD was called a CDC/differential circuit breaker) the Double pole MCB's will help find the fault,
are the hob and oven on the same MCB?