My RCCD unit sometimes trips when I turn my main oven on

it could or a short in wiring ---circuit need a meter and test the system

You have a short, probably a wire came loose and is welded to the frame. I assume hte consumer unit is the braker for the stove in your panel.

The elements in ovens consist of an outer earthed metal tube and an inner resistive element that is insulated from the outer tube by what is effectively a compressed ceramic insulating powder. If the element is not used for a while, enough atmospheric moisture, (or from spills, etc), can penetrate the insulation to cause enough earth leakage to trip the RCD. If the RCD is tripping at the correct level, (They can get too sensitive - see this article here:
Diagnosing RCD earth leakage breaker nuisance trips), then the only long term solution is to replace the element, although they can sometimes be dried out by heating them.

your heater elerment has gone in the main oven i had the same problem if you need help takeing it out and see if its the problem get back to me ok

If you are sure there is 220v going to unit, it most likely is element or click / control. If you have a ohms meter, you can test the element

you need to upgrade your beaker

Sounds to me to me like a direct short. Hot wire in unit could be touching part of unit. Oven switch if it has one or main board could be shorted. Oven will have to be pulled to check. Slimm possibility weak breaker.

I have a u1421 with the same problem! I notice the fan doesnt run too well, sometimes it doesnt run at all, needs a prod to get it running. I suspect with no fan, that the element gets far too hot, and then starts to leak to earth, tripping the RCD. I'm gonna try buying a new fan motor - you should ckeck if your fan is running full speed OK.

You may have had a surge during the storm. Check main control board in console for damage.

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We need wiring diagram for HB905 Siemens double oven, to start with it kept tripping, element ok. Now we have no heat coming from the main oven.