Diagnosing/repairing an oven

[Ben Blaukopf]

I've been given a built in oven (electric). I wired it up last night, turned it on, and promptly tripped the RCB for the flat. It now appears to be electrically dead - that is, supplying it with power doesn't even trip anything. Which suggests the fault lies there. The switch unit on the wall still provides power out of the socket, so I'm assuming I haven't blown anything there (does a cooker unit have its own fuse?). It is, of course, on its own 30A circuit

The oven is a white double oven Ariston TC714. I don't have a manual for it, nor can I find any information on the web about it. Nor can I find anything useful about oven repair (except for microwaves!).

The only possibility that has occurred to me is that when the oven was removed from the old kitchen (not by me) someone dropped something - e.g. a screw in it, thereby shorting it. I know nothing about the workings of an oven. I am happy to go prodding with a voltmeter though, if someone can suggest where to look.

Any help/pointers very welcome,

TIA

Ben

[usenet]

Do you mean RCD or MCB? If it tripped the RCD that may well be par for the course until it's heated up properly and dried out the elements so the leakage reduces to an RCD-non-tripping level.

Oven elements are well known to often be marginal as regards leakage and even 'good' ones can sometimes trip RCDs.

It's odd that it now doesn't work at all, usually ovens are pretty simple things. Does it have all sorts of clever automatic timers etc.? If so it may well be that you have to press seven buttons at the same time and stand on one leg to get it out of some mode where you can't get the oven to turn on.

[John Key]

two usual causes:

wiring at the back of the oven has been dislodged in the move and needs checking

or

timer switch has been turned on and needs returning to manual.

after that poke around with a wet finger (joke)

JK

[Ben Blaukopf]

RCD :)

I don't know how I concluded it was dead yesterday. It's now back to tripping. I measured the resistance across live and earth and got over

1Mohm. Neutral is effectively completely isolated. So surely the current leakage should be less than 30mA and the RCD shouldn't trip (it goes as soon as I flip the switch on the connection unit)? I realise I'm probably missing something...

I've left the doors open for ventilation - I'll see how the resistance varies...

It does :(

Ben

[Andrew Gabriel]

The resistance might look quite different with mains across it.

An oven doesn't need to be on a 30mA RCD, and the metal sheathed mineral insulated elements when cold are allowed to leak, which means it's not a good idea to have it on a 30mA RCD or you can never warm it up;-). You would normally only need it on any RCD if the supply is a TT type, in which case it should be rated 100mA or more.

When PAT testing a non-portable appliance with metal sheathed mineral insulated elements, if the leakage is too high, you are supposed to repeat the test again having run the appliance to warm up the element. This issue most often arises if the appliance hasn't been used for a while.

[MattG]

You could try emailing Ariston UK and telling them you've lost the manual and ask for a replacement.

That's what I did with my Mothers second hand Delongi microwave, they sent a photocopied manual out first class, no charge.

Worth a try.