Built in cooker oven burning though housing shelf

[anrkyuk]

Last week my mothers built in cooker oven kept tripping the RCD when switched on at the wall. I removed the oven and the melamine shelf it had been sat on had been burnt through and the cable about 6 inches down from where wired into the oven had been burnt back to the copper. It looked like the oven was sitting on the wire.

I replaced the melamine shelf with same thickness tongue and groove flooring, cut the cable back and put an oven outlet box on the wall behind the oven and rewired the oven making sure the cable was well away from the shelf / oven.

The first time she cooked with it, itwas fine. Today the kitchen was filled with the smell of burning wood. The shelf the cooker sits on was warm around the edges and in the middle where the previous shelf had burnt though was too hot to touch.

At the moment I am letting the oven cool before pulling out to check the shelf.

The only thing I can think of is to once cooled switch just the top oven on for a while to see if the shelf gets warm, if it does not I can only assume the insulation on the base of the bottom oven has failed and that if it still warms up with just the top oven on that it is some kind of electrical fault, either way it looks like a new cooker.

Any thoughts or ideas to avoid this would be most welcomed indeed

Many thanks in advance
A

 

[anrkyuk]

First as the oven was cold I pulled the oven out and in the exact same spot that the previous shelf had burnt the new wooden shelf was blackened. The cabling was however fine.

I then switched on just the top oven at 200c for 30 mins, this did not effect the shelf as was cold to the touch.

Reading the manual something came to note, it said that there should be a 5cm gap top and bottom of the oven and vents above and below.

The top of the oven has only a 2cm gap and the bottom technically has none ( there are 2" struts on the bottom of the oven raising the base of the oven from the shelf so the base of the oven is not in contact with the self so not sure if that counts but still is only 4cm not stated 5cm required )

However this oven has been in place nearly 16 years and odd that only just started to happen so lack of ventilation I do not belive to be to root problem, probably just made worse due to this.

Checking under the oven the metal appears to be bright galvanized, in the area that the shelf has burnt the metal is dull with slight brown patches ( again noting this is not in direct contact with shelf )

Given the following an uneducated guess is that the insulation on the bottom of the oven has failed and the lack of ventilation in the area has caused the shelf to burn.

I'm going to remove the shelf I installed yesterday and making some struts create a 50-100mm void under the oven however given the age of the appliance I am unsure how / if I will be able to replace the insulation, any thoughts ?, worth getting a repair man out to it, or ?, any advice is welcomed.

Regards
A

 

[Burnerman]

Regard this one with massive caution.....either the insulation has collapsed or there may even be arcing within the oven carcass due to element coverings disappearing.
The last thing in the world you need is a fire - I'd consider replacing this appliance straight away.
John

 

[anrkyuk]

Thank you very much for your reply.

I have just spoken with my mother and I wanted to ask before ordering a new oven. Mum is worried ( has been convienced by others ) that there is insufficient ventilation in the oven housing. I am unsure as this was fine for over 15 years before this has happened.

As described above how does it sound ?, an easy option would be to add 80mm vent hole with grills above, below and on the side at the back to improve ventilation. Expanding the gap above the oven is impossible and below diffictult and slightly costly but not impossible.

I'm assuming that from my test yesterday that she is safe to use the top oven as with my test last night when the top is on the shelf did not warm up.

Many thanks in advance
A

 

[Nozzle]

Is there normally a running fan to force ventilation which has now failed or clogged up so much it doesn't flow well? Just a thought, addressing the apparent change in behaviour after all these years.

Nozzle

 

[anrkyuk]

It is a fan assisted oven, there is a fan in the main oven but that is only for circulating the air in the main oven. On the outside of the oven ( back top, bottom and sides there are no holes, vents etc.

The only vents are on the front. There is one front top above the smaller oven which is an actual vent for the oven, the other is a small vent front bottom under the main oven, this vent is not for the main oven but rather a vent for the 2" gap under the oven as stated above ( the oven sits on a shelf, the oven has 2" sruts lifting the base of the oven from the shelf and this vent is for this void ).

I have spoken to a local electrical supplier that my father purchased all his appliances from Joe Grahams In Luton, they advised that the housing is fine as described.

I am going to add one of these in the shelf the oven sits on, the shelf above the oven and one on the side

http://uk.rs-online.com/web/p/produ...-3633baf8113b&istItemId=xwimxtqll&istBid=tzit

And then replace the oven.

We used the top oven again this evening and again was fine, shelf the oven sits on did not warm up and difinatly no burning smell.

I don't think its just the insulation thats failed due to the dull patch on the metal underneath where it was burning the shelf esp as it was not in direct contact, something is super heating a 4" patch of metal under the oven.

Again thank you for all your assistance

Regards
A