Oven Isolator Switch

nickdel · 18 Jul 2007

My fuse blew on the 30 amp circuit so I replaced it and switch on my oven, all was fine. The next day the fuse had blown again so I replaced the fuse wire again however this time when I switch on the oven a very large spark appeared from the socket. Checked the main fuse and it had not blown. If I switch the mains power on and off the same large spark appears (still doesn't blow the fuse!).

Could this just be a faulty socket? If so, is it ok to put a 45amp socket on the 30amp circuit? Haven't been able to find a 30amp socket!

Thanks

Nick

ricicle · 18 Jul 2007

Sounds like you have an intermittent fault on the oven or a worn switch.I would recommend the services of a competant electrician to sort this out for you

JohnD · 18 Jul 2007

when you say "oven" do you mean "oven" or do you mean "cooker?"

When you say "socket" do you really mean "socket?" or do you mean "switch?"

Is it in a commercial kitchen, or a house?

What colour is this socket? Red or blue? Can you post a pic?

nickdel · 18 Jul 2007

John, it's a standalone oven and it is wired directly into a switch which says "Cooker" but also has a 13a socket on it.

This is in my house, oven is only about 1 year old and has been working fine, infact hadn't even been using oven when main fuse (30a) blew the first time.

Nick

nickdel · 18 Jul 2007

Sorry, can post a pic but looks just like this

http://www.screwfix.com/app/sfd/cat/pro.jsp?id=23484&ts=89012

Nick

JohnD · 18 Jul 2007

if it's just a single oven, it should take about 12Amps and should not blow a 30A fuse. If its a double oven it should take about 20A and not blow a 30A fuse.

If it's just an oven that the electric cooker circuit supplies then you must have a gas hob with rings in the kitchen as well.

If you have a 30A fuse it is probably very old.

If the fuse blew once and then not again, this often happens when there is a nail through a cable, as the short-circuit burns away the touching wires. It remains very dangerous and we know a case where a cutlery rack was screwed to a wall and the screw penetrated a cable and killed the householder.

It sounds like you mean the flash is coming from the switch. The switch might be faulty. Or there might be a fault on the oven or the cable (e.g. a nail or screw through it).

If the flash and the blown fuse happened when the oven was not turned on then it is quite likely a damaged cable, but obviously none of us can see it from here.

If you post some pics of the consumer unit (fuseboard), cooker switch, socket and any visible cable we may have some more ideas.

I agree that you need a qualified electrician to trace the fault.

oven

cooker

gas hob

electric hob

securespark · 18 Jul 2007

JohnD said:
it is quite likely a damaged cable, but obviously none of us can see it from here.

It would have to be a very big bang for that to happen!!

nickdel · 21 Jul 2007

Thanks John, as it happens and I'm only just thinking about this now, I recently had a new bathroom fitted, the kitchen is past the bathroom and I'm assuming the cables run past this at some point. I am now concerned that at some point during putting up the new plasterboard that a nail has penetrated the wire.

Is there anyway I can test this? My only access to the wire now would be to knock a hole in the wall which is obviously not on the top of my to do list!

Also, seeing how I've just splashed out 5k on a new bathroom, is this likely to be an expensive job to fix if I need to get an electrician in to repair/replace the cable?

Nick

electronicsuk · 21 Jul 2007

I would be more inclined to blame the switch or the oven than anything else based on what you've told us so far.

In the event that the cable has been damaged then it might be difficult to locate the exact point where the damage has occured. If it can be pinpointed then it can be repaired without the need to run a completeley new cable, so it shouldn't be too expensive. The preferable solution would still be an entirely new cable, but clearly this is going to be a lot more expensive and likely to cause disruption to the work you've already had done.

Finally, in answer to your original question...

Yes, you can use a 45A switch on a 30A circuit, as the rating of the switch is equal to or greater than that of the protective device (the 30A fuse in this case). A qualified electrician will have the test equipment necessary to deem whether or not the fault is with the switch, cooker, or elsewhere in the circuit.

breezer · 21 Jul 2007

only briefly read the post, i submit the problem is not the cable but the cooker since the flash from the switch is natural becuse that is whe it gets connected to the supply, its not an electrician you want but an aplliance engineer

nickdel · 21 Jul 2007

Thanks Guys, mind at rest a little. Could it really be the oven though (it's a stand alone oven, have gas hob). When I replaced the fuse wire for a second time, I turned the oven on, there was the big spark again, fuse didn't blow and oven was still working just fine!?

Nick

electronicsuk · 21 Jul 2007

nickdel said:
Thanks Guys, mind at rest a little. Could it really be the oven though (it's a stand alone oven, have gas hob). When I replaced the fuse wire for a second time, I turned the oven on, there was the big spark again, fuse didn't blow and oven was still working just fine!?

It's possible there's an intermittent fault with the oven. It could even be the case that the switch has been damaged by excess current from a faulty oven which is now resulting in arcing across the contacts. Get someone in to diagnose the fault - the best we can do right now is make educated guesses.

davy_owen_88 · 21 Jul 2007

Is the oven itself switched on when you operate the 'cooker switch'? I.e is the isolator making/breaking a loaded circuit? If not, then the flash is indicating a problem, possibly a loose connection or a faulty switch.

Turn off the 'leccy and have a look behind the 'cooker switch'. Take a picture and post it up for us all to see

JohnD · 21 Jul 2007

good point

A switch should not spark unless it has a substantial load on it. Even then, unless it is very worn or is damaged, you wouldn't get a visible spark at switch-on, only at switch-off.

Might be a worn out switch though, or a damaged oven flex esp. if something heavy has been put on top of it (like the oven)

Usually the oven or cooker is connected via a large outlet in the wall. If you disconnect the oven cable from here, and put in some other large load (e.g. a fan heater, iron or a toaster) does the problem recur, or does it go away when the oven goes?

If, as you say, it is just an oven, does it have a flex on it or a stiff plastic cable connected to the wall?

In the event that the cable has been damaged, a good electrician would be able to identify the fault within not many minutes.

nickdel · 21 Jul 2007

Ok, well I couldn't figure out how to upload an image here so I've stuck something on my own site.

Basic scenario:

Power is off
Oven/Cooker switch is set to on
Oven is off
I switch the leccy back on
Big spark from socket

here's a video, it's about half way in just as you hear a beep (which is my phone)

http://www.nicksplaysite.co.uk/leccy/leccy.html

Cheers

Nick

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Oven Isolator Switch

breezer

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