Baumatic B144SS fan oven sometimes trips RCD after random amounts of time.

[teuchuno]

As the title says, we have a 10 ish year old fan oven which has started tripping the RCD. I replaced the element about a fortnight ago due to it getting damaged by a screw working itself loose and the element coming into contact with the fan. It has been running fine since then, the problems seemed to start after I slow roasted in it (so it was on for 6 hours at low temperature).

So far I've checked the element (26 ohms, seems to be about right). The element is also heating up no problems and the wiring to it is secure and undamaged. It is glowing red, but I assume it is meant to. Is there a chance it is overheating?

I've tried gently moving the heat up, 25 degrees at a time to see if there is a temperature at which it trips; this doesn't seem to make a difference and it still trips at seemingly random temperatures (125 one time, 250 the next etc).

I think it must be the thermostat, as the thermostat light is on when the cooker is off, although it goes off when the oven reaches temperature, but I assume that it shouldn't be on when the fan oven setting is off. Similarly, I suppose if the thermostat is NFG then the element may be drawing too much current, causing it to trip?

Does it sound like the thermostat needs replaced? Or is there a chance there is more going on?

Thanks in advance.

 

[flameport]

A thermostat is an on/off switch - even if faulty it will not cause the problem described.
The light being on when the oven is off is unusual, but if it clicks off when the temperature is reached, it is obviously working.

The most likely cause is moisture somewhere it shouldn't be - defective elements being the most likely cause, condensation within the insulation is also possible but less likely.
Doesn't have to be the element in use either - if the oven has other elements (top/bottom/grill) one of those could be defective and causing the problem, even though that particular element is not switched on at the time.

If it has other elements, switch those on, wait for it to get to full temperature and leave on for at least 15 minutes, which will either dry out any moisture there, or cause the defective one to fail, after which it will be easy to identify.

 

[teuchuno]

Aye that seems to have done the trick. Problem was that I couldn't get it to temperature to evaporate the moisture, but managed (for some reason...) to get it to max without it tripping. Left it on for half an hour and no probs since.


Thanks very much!