Oven still tripping rcd?

[noidea27]

Hi.

Zanussi oven. 10 years old. Couple of months ago, main oven was blowing the fuse. Replaced the element and fixed it, no problem.

2 months on, main oven has been blowing fuse again. Strangely it had been taking 5/10 minutes of being on before it blew. In previous experiences a bad element simply wouldn't heat up and would trip out within a few seconds.

Bought a new element again (hoping the second was a dud) but the exact same thing is happening. Oven getting hot but tripping after 5/10 mins.

We had the top oven on full whack earlier with no problem so I would suggest that would rule out an electrical issue outside the oven itself?

If not the element, could the fan be the issue? Although this seems to be running okay when the oven is on.

So, worth trying to figure out anything else or is it new oven time?

Cheers

 

[EFLImpudence]

There is a big difference between tripping an RCD and blowing a fuse so which is it?

 

[noidea27]

Apologies. It's tripping the RCD.

Just been back to the oven and turned the knob to turn the lamp on only (no heat) and that also tripped the RCD.

 

[ericmark]

Tripping on a dedicated RCBO then likely the element at fault, tripping a general RCD covering many circuits, you do need to test. I tested my own consumer unit, and for a single RCD it would be right on the edge. Permitted 30% or with a 30 mA RCD 9 mA, but only way is to test, for an oven I would tend to use an insulation tester, but to buy parts without knowing what is at fault is not really the way forward.

 

[noidea27]

It's definitely not the element. I simply turn the oven light on and it trips within a couple of seconds.

 

[Taylortwocities]

It's definitely not the element. I simply turn the oven light on and it trips within a couple of seconds.

Then there is another fault in there, perhaps a frayed piece of wiring. You are going to have to start disconnecting one item at a time until you discover the faulty item.

 

[jj4091]

What is the model number

 

[noidea27]

What is the model number

Zanussi ZOF35501XK (94417154301)

 

[jj4091]

Fistly try disconnecting and insulating the wires to the element then switch on again and leave for some time.If it does not trip that should suggest it is element related. Sometimes new elements can absorb moisture into the insulation, though it seems unlikely when it will heat for some time.
It could possibly be the fan so perhaps disconnecting that both with and without the element connected might show up something.
It sounds like something is touching the frame or covers somewhere as the oven heats and expands so if you cannot see any broken or burnt wires anywhere then try running it with the rear cover off.
Other than that it will be a case of tracing all the wires that have anything to do with the main oven to find some where that the insulation is rubbing against the frame.
Start at Item 3A shown here on the exploded diagram for electrical equipment https://www.ransomspares.co.uk/parts/brands/zanussi/cookers-hobs/zof35501xk (94417154301)/?gad_source=1&gad_campaignid=1531799912&gclid=EAIaIQobChMI4831lOjujwMV3plQBh2f8AENEAAYASAAEgLuqPD_BwE

 

[Harry Bloomfield]

Sometimes new elements can absorb moisture into the insulation, though it seems unlikely when it will heat for some time.

They can heat up, and expel the moisture, then reabsorb it whilst cooling.

There is also a likelihood, that the neutral remains connected to the element, and the live switched. That would mean the RCD/RCBO could trip, simply on the neutral to earth leakage from the element. The only way to confirm it, is as above, try disconnecting BOTH terminals from an element, insulate, and retest.

 

[jj4091]

They can heat up, and expel the moisture, then reabsorb it whilst cooling.

There is also a likelihood, that the neutral remains connected to the element, and the live switched. That would mean the RCD/RCBO could trip, simply on the neutral to earth leakage from the element. The only way to confirm it, is as above, try disconnecting BOTH terminals from an element, insulate, and retest.

I did write "wires ' to the element

 

[Harry Bloomfield]

I did write "wires ' to the element

Without troubling to explain why!

 

[jj4091]

Do you think it needed explaining

 

[Harry Bloomfield]

Do you think it needed explaining

In this case - yes - The OP might assume that just removing one terminal might be enough. In fact, I've known claimed pros, not grasp the principle.

 

[noidea27]

Thanks all. Changing an element is one thing but further testing/fault finding is a bit beyond me and tinkering with something like an oven is probably not advised. Ive got an electrician coming over to look. Difficult one as fault finding/fixes might end up being more trouble/costly than just buying a new oven?