Smeg suk61mfx5 cooker blowing fuses

[iep]

I have just taken a chance on a faulty second hand smeg oven. It's a dual fuel model with four gas hobs and an electric oven.

The fault is that when the oven is switched on, it heats up fine for about five minutes and then trips out the fuse box. This is info from the seller (I haven't picked it up yet) so I don't know if it is triggering their MCB or their RCD (I'm guessing MCB as people don't tend ot put dedicated cooker circuits on the RCD).

Apparently the fan, controls, clock etc, all wortk fine. So, my theory is that the element may slightly deforming as it heats up and only then becoming a short circuit.

Does anyone have any ideas on this before I buy a new element for it?

Cheers,

iep

 

[jj4091]

(I'm guessing MCB as people don't tend ot put dedicated cooker circuits on the RCD).


iep

I would not bet on that, but either way faulty element most likely to be the problem.It could however also just be a wiring or burnt connector fault, so I wouldn't buy an element before I was sure. Do you actually have ownership of the oven already, if so then just disconnect the element & see if the fault dissapears.

 

[iep]

Thanks for that. I don't pick up the cooker until Saturday but I'll do as you suggest and switch it on after removing the element to see if it still blows the fuse. Fingers crossed it'll just be that.

Cheers,
iep

 

[iep]

I picked up the cooker yesterday and plugged it in today (13A fuse in the plug and using a spare 16A radial circuit in the garage for safety).

I can't get it to blow the 13A fuse in the plug let alone the 16A fuse in the fuse box. I have used all combinations of oven elements and fan setting and let it heat up to max temp for 20 mins on every mode (the garage is now sweltering!). Not only that but I used an inductive current probe to check current consumption and it is exactly correct (works out at the rated 2kW). There really seems to be nothing wong with it.

Looks like I have done well but I can't help but wonder what might have been causing the problem in the previous owners house. My guess is that it was tripping his RCD (although he was adamant that it was the MCB that was going) or that he simply had a wiring fault in his house.

We have an old rewirable fuse box so no RCDs, perhaps that is why it is working okay?

iep

 

[Leccy758]

Its possible that the RCD was blowing, you could always check by using a plug in type rcd and plugging the oven into that and testing each circuit in turn.
Not uncommon for elements to short to earth when they get hot and if you are not on an RCD you wont really notice apart from the possibility of getting a shock from the appliance.

 

[iep]

Hi Leccy758. I was thinking just that so I put a current meter in series with the earth connection to the cooker. Left it on to get hot abut still measured no earth leakage at all. This is consistent with the former owner telling me that it was the MCB that tripped.

Had another look around the back of the appliance with the cover off and then noticed a very small discoloured spot on the inside of the casing. This spot was just at the centre of a minor dent in the panel. When I held the panel back up against the appliance I realised that the spot lined up exactly with the live connection to the cooker element.

So, basically a minor dent in the back panel combined with the oven being pushed up against the wall in the former owners kitchen meant that the casing was within a fraction of a centimetre of touching the element's live contact.

Add a bit of heat expansion and the casing would get close enough to contact and then the MCB would blow.

So, hammered the dent out and hey presto, should be solved.

iep

 

[Leccy758]

sometimes its the simplest of things.